Welcome To Winter, A Little Dew Point Talk & Well Wishes To Flt. 1404

Welcome to winter? Some of you are probably saying have you checked the weather reports lately.

Old man winter has slammed much of the country with wicked weather, in particular, the northern half of the country.

Although winter storms have been impacting us for quite some time, winter officially just arrived yesterday, along with the shortest day of the year in terms of sunlight.

So there is a silver lining to this for all those ready for spring --- it's an uphill climb from this point forward.

Days will slowly but surely grow longer and before you know it, spring will be here.

Winter continues to chill the Pacific Northwest, with more snow for Seattle and Portland.

Snow is also flying around the Great Lakes and in the northeast as the latest weekend storm pulls away.

In between, it is just plum cold for millions!

Single digit temps can be found all the way into northern Arkansas, with teens nearly to the Gulf of Mexico.

Locations on the immediate Gulf Coast are hovering in the upper 20s to middle 30s for the most part.

Over the weekend Bill from Missouri left a blog comment asking about his weather station's recording of a negative dew point temperature.

And WxWatcher from Missouri did a great job answering.

Indeed you can have a negative dew point temperature, just like we sometimes get negative air temperatures.

All a negative dew point means is that the air mass overhead is very dry.

When looking at a dew point, just consider it a guide as to what the air temperature would have to cool down to for the atmosphere to be completely saturated.

Meteorologists often use the dew point for helping predict the overnight low temperature, esp. this time of the year.

You see, the air temperature cannot drop lower than the dew point. And in the winter, it's often a good indicator of how low the temps may go overnight.

So it is was 4 pm, clear skies, 10 degrees above zero with a nice, fresh and somewhat deep snow pack, and a dew point of negative 10, as a forecaster, I would first figure out what the winds were going to be doing overnight.

If they are expected to be light to calm, I'd go for an overnight in the -5 to -10 degree range, using that current dew point of -10 as a guideline for the lowest possible overnight low.

The problem is things change.

Two hours later, that dew point could have risen to -5 if moisture advected into the region, or dropped to -19 if drier air had moved into the area.

Regardless, it is still a great weather parameter to monitor when trying to figure out how low the temps will go.

And finally, I know most of you heard about the crash of Continental Airlines flight 1404 here in Denver over the weekend.

All I can say is THANK GOD all 100+ passengers/crew survived.

I cannot even begin to imagine what they have been through, nor do I ever want to experience it.

I read a very well written story this morning online as one passenger accounts his experience.

Click here to read it.

So if anyone from the flight reads this blog,I am so glad you are alive, and I wish you a speedy recovery.

Vegas Hits Jackpot

I stole that title from the National Weather Service's story, but it's just too good. See below.

...LAS VEGAS HITS THE JACKPOT FOR SNOW IN DECEMBER... AN ALL-TIME RECORD SNOW FOR THE MONTH OF DECEMBER IN LAS VEGAS WAS SET YESTERDAY DECEMBER 17TH 2008. 3.6 INCHES OF SNOW WAS MEASURED AT THE NATIONAL WEATHER SERVICE OFFICE LOCATED ABOUT 2 MILES SOUTHWEST OF MCCARRAN INTERNATIONAL AIRPORT. THIS BROKE THE RECORD FOR THE MOST SNOW EVER IN THE MONTH OF DECEMBER IN LAS VEGAS SINCE THE START OF OFFICIAL RECORDS IN 1937 WHICH WAS 2.0 INCHES ON DECEMBER 15TH 1967. THIS IS NOW THE 8TH GREATEST SNOWSTORM EVER IN OFFICIAL LAS VEGAS WEATHER RECORDS FOR ANY MONTH. THE 3.6 INCHES OF SNOW MEASURED YESTERDAY ALSO SET A NEW DAILY RECORD FOR SNOW FOR DECEMBER 17TH BREAKING THE OLD RECORD OF A TRACE SET IN 1992. MEASURABLE SNOW HAS ONLY FALLEN ON 5 INSTANCES SINCE 1937 IN THE MONTH OF DECEMBER IN LAS VEGAS COUNTING YESTERDAY...2.0 INCHES OF SNOW WAS MEASURED ON DECEMBER 15TH 1967...0.4 INCHES OF SNOW FELL ON DECEMBER 5TH 1972...1.0 INCH OF SNOW WAS RECORDED ON DECEMBER 6TH 1998 AND MORE RECENTLY 1.3 INCHES OF SNOW WAS RECORDED ON DECEMBER 30TH 2003. THUS THE 3.6 INCHES OF SNOW THAT FELL YESTERDAY IS THE MOST SNOW TO EVER FALL ON A CALENDER DAY IN DECEMBER IN LAS VEGAS. THE 3.6 INCHES OF SNOW THAT FELL AT LAS VEGAS YESTERDAY WAS THE MOST SNOW TO FALL IN LAS VEGAS FROM A SINGLE STORM SINCE 7.8 INCHES OF SNOW FROM JANUARY 30TH THROUGH FEBRUARY 2ND IN 1979. DECEMBER 2008 WILL NOW RANK AS THE 6TH SNOWIEST MONTH EVER IN LAS VEGAS SINCE 1937. THE SNOWIEST MONTH EVER WAS WAY BACK IN JANUARY 1949 WHEN 16.7 INCHES FELL. THE LAST TIME THIS MUCH SNOW FELL IN ANY MONTH IN LAS VEGAS WAS IN JANUARY 1979 WHEN 9.9 INCHES FELL. SNOWFALL RECORDS IN LAS VEGAS WERE RECORDED AT MCCARRAN INTERNATIONAL AIRPORT THROUGH JANUARY 31ST 1996 AND SINCE FEBRUARY 1ST 1996 HAVE BEEN KEPT AT THE NWS OFFICE ON DEAN MARTIN ROAD. IN ADDITION...A DAILY LIQUID PRECIPITATION RECORD WAS SET AT MCCARRAN INTERNATIONAL AIRPORT YESTERDAY WITH 0.73 INCHES OF PRECIPITATION RECORDED. THIS BROKE THE OLD RECORD OF 0.44 INCHES FOR DECEMBER 17TH SET IN 1940. THIS ADDITIONAL PRECIPTATION BROUGHT THE DECEMBER MONTHLY TOTAL UP TO 1.02 INCHES OF LIQUID. THIS MAKES FOR THE 9TH WETTEST DECEMBER ON RECORD. ALSO...THE HIGH TEMPERATURE ON DECEMBER 17TH ONLY REACHED 39 DEGREES. THIS BROKE THE PREVIOUS LOW MAXIMUM TEMPERATURE RECORD OF 43 DEGREES SET IN 1967.

Three Dog Night

The other night when it was -19 here in Denver, the bassets were huddled on the couch warming up after going out to potty.

Here is a cute picture.



Cold and unsetteld weather remains in the future for many as winter approaches, as well as the shortest day of the year.

A new storm system is moving into the northwest while the most recent one exits the northeast.

The CoCoRaHS maps and comments have been busy as of late, with many of you reporting snow.

Just look at how much of North America has snow on the ground today!

Need To Warm Up? Head North! Plus, Read About Cold Science Fun!

Head north? What?

Can you believe that as I type this blog, it's 24 degrees ABOVE zero in Barrow, Alaska -- and 24 degrees BELOW zero in Glendive, MT.

There are some below zero temps in the interior of Alaksa, but a pretty amazing statistic nonetheless --- considering Barrow is usually in the deep freeze!





It was a brutally cold -19°F in Denver overnight. That set a new record low for the date.

We've been holding at about -13°F to -10°F for the past few hours.

I have a science experiment for those of you in the deep freeze.

Boil some hot water on the stove or in the microwave. About 1/2 a coffee cup's worth, maybe slightly less.

Get a good grip on the handle, go outside, hold the glass at your waist and then with all your might, raise your glass, throwing all the water straight into the air.

You will make a cloud as it instantly turns into water vapor!

The colder the better. I tried it last night when it was about -7 or -8°F and it worked, but some drops of water fell back to the ground. (so when you loft the water into the air, do it at a slight angle away from you or you might get a little wet!)

Once you get into the minus teens or lower this experiment really works well.

The trick is the hotter the water, the better. So pour your coffee cup and immediately get outside and launch the water.

The higher you hoist the water the more dramatic.

Ice storm warnings are in effect for the mid-south, from east-central Arkansas into western Tennessee.

Areas around Memphis could see up to an inch of ice -- repeating what we saw happen to New England a few days ago.

Winter Storm Warnings cover the Ohio River Valley.

And in the upper midwest and the high plains, it's just plum cold! Dangerously cold in many locations.

A winter weather advisory is in effect for the greater Las Vegas area for up to 2 inches of snow! Some flakes may even fly on the strip!

And in southern California, who sang that it never rains?

Heavy rain is currently falling as I blog over the Los Angeles area, with flash flooding a threat over all the burn scars from recent fires.

In the mountains of Los Angeles, Ventura and Santa Barbara counties, a winter storm warning is in effect for 12-18 inches of snow!

And talk about weather weenies, these are my kind of guys and gals.

The folks at the National Weather Service office in Seattle/Tacoma made a great powerpoint recap of the winter storm that hit over the weekend, bringing a rare snowfall to downtown Seattle.

Click here!

After such a BORING fall season, the weather has become quite active and in many cases dramatic and out of the ordinary these past few weeks.

Snow in Houston, New Orleans, Jackson, Seattle, maybe today Las Vegas?!?

Crippling ice storms and a cold fornt that made many locations in the middle of America drop 50 to 70 degrees in 18 to 30 hours.

Here in Denver we were 58 degrees on Saturday afternoon and minus 19 degrees about 2 am Monday. That is a 77 degree change in less than 2 days.

Is it dramatic climate change? And aren't we supposed to be in the middle of global warming?

In some cases yes, I think climates are changing -- but I'd also pose that in some places where they think climates are changing, maybe it's just a really "out of whack" weather pattern that takes a few years to correct.

Who really knows?

That's why we track weather data -- more and more now than ever before -- so there is written documentation to compare the present with the past.

And some research does show the planet is warming. But it is just part of the planet's cycle? Or are humans causing it?

Who knows?

Regardless of what is happening on the big, long-term picture, it doesn't stop Mother Nature from showing us her awesome power and it doesn't stop the forces that control weather on Earth from showing us the extremes.

Climate is a delicate system that always returns to a point of equilibrium and those frozen today will thaw out, and those bone dry will eventually get wet, those too wet will dry out and those too hot will some day cool off.

The frustrating thing is it doesn't always happen on a time scale we like -- but that is kind of the beauty of it.

In a world of self-gratification and I want it now, Mother Nature sometimes says you know what, you'll have to adapt!

Don't forget that I have changed the settings for leaving comments so it should be MUCH easier now for you to chat with me and all the blog readers.

I love hearing from you.

Have a great day and please stay safe and warm!

Can You Find The Low Pressure?

Click the image below and it will open a bit bigger.


That is the "tightly wound" area of low pressure responsible for sucking down sub-zero air from the heart of northern Canada.

Good morning from Denver where the temperature is hovering from 0 to -2°F. It was 58°F above zero here in the Mile High City just about 18 hours ago.

We picked up a fresh blanket of white overnight, enough that I'll be heading out to shovel in a little while -- perhaps when we hit 5 above!

Back to the surface map I attached to this blog -- so it was pretty darn easy to find the low, right?

Now here is a challenge -- click on the picture again and this time draw the cold front. It is somewhere between Minneapolis and Fargo.

That short 3 hour ride up I-94 takes you from 36 above to 7 below zero!

Isn't weather exciting -- and so powerful.

North Dakota is all but closed for business today as I-94 is nearly shut down border to border, and I-29 IS shut down border to border.

And can you see why? As I type, the report coming out of Fargo is a balmy -8°F, heavy snow, and a sustained wind of 33 MPH gusting to 44 MPH out of the north.

There are some pretty good snow totals coming in from that region, with nearly a foot of new snow between Williston and Bismarck.

If you are a weather nerd like myself, and read some of the storm reports from that part of the world, you will notice sometimes the snow reports are estimated.

And that is ok -- in areas where wind blows the snow all over, including here at my house in the eastern suburbs of Denver where either there are no trees OR all the trees are new and offer no protection, sometimes you just gotta do your best to put the pieces of the storm puzzle the wind blew around back together.

In the Pacific Northwest, 38" of snow has been reported at June Lake on Mt. St. Helens.

And 1-3" is on the ground now in the greater Seattle metro area.

I was asked what kind of weather is associated with the occluded front in Friday's blog?

Typically along or ahead of the occlusion the weather is unsettled, cloudy and often wet. Overcast may be a good way to describe it.

Behind it things improve.

Because this is where one air mass overtakes another in a storm system, the weather can be extremely variable over a short distance.

So in the picture below, you can see the storm --- a cold and warm front associated with a low pressure.

At the top, where all the weather wraps back into the low pressure system (counter-clockwise circulation here in the northern hemisphere) the two air masses blend into one and form an occlusion.

More About Fronts

A few weeks back I did a string of blogs all about fronts.

I just realized I never finished up with the occluded front.

When a cold front catches up to and over takes a warm front, the boundary between the two air masses is called an occluded front.

Or simply, an occlusion.

It is drawn on the surface weather map as a purple line with alternating cold-front triangles and warm front half-circles.

Both symbols point in the direction the air mass is moving.

You can have an occluded front opposite of the one I described above. In otherwords, the warm front can catch up with the cold front, but it isn't as common.

Wacky Winter Weather

Wow what a busy day for meteorologists in almost all parts of the country!

First the good stuff -- snow in Houston, Galveston, New Orleans, Baton Rouge and Jackson!

It was the first snow in Houston since Dec. 24, 2004 -- and only the 7th snow in New Orleans in 60 years!

As you can imagine, the snow wreaked havoc on the roads, with all kinds of accidents and closures.

The Mississippi River bridge on I-10 is closed as of this blog posting.

I went to a few television station web sites and looked at viewer pics. I know from growing up in Arkansas the excitement a snowfall brings to people of all ages in that part of the world.

And let me tell you from experience, this isn't a dry and fluffy snow like we are used to here in the Rockies.

This is like taking a spoon full of mashed potatoes and plopping it onto the floor.

It is a very high water content snowfall -- perfect for making snowmen and snowballs.

Here is a great web site with links to media outlets by state. Click here.

The same storm bringing snow to the south is also bringing heavy rain the areas thirsty for moisture -- I am talking about the drought stricken areas of Alabama, Georgia, Tennessee and the Carolinas.

A widespread 1-3 inches of rain has fallen here, with some locations recording over 5 inches near Huntsville, Alabama.

In the northeast, heavy rain is falling from Boston to D.C. with a significant icing event expected from Albany, NY to portions of Maine.

After the ice will come the snow -- making for a miserable time in this part of the world.

And in the northwest, a new storm moving onshore will bring cold air and rain/snow -- with snow levels eventually dropping to sea level by Sunday.

This will spread into the Rockies and across the northern tier of states heading into next week, along with bitterly cold air.

Temperatures may not get above zero in some of the northern states come Monday and Tuesday!

If you are looking for quiet weather, you pretty much have to head to the deserts of the southwest.

I have made some changes to the setting for leaving comments on the blog. It should make the process a little easier for you to communicate now.

Complex Winter Storm

A large storm system has swept across the center of the country bringing everything from snow to tornadoes.

In fact, much of central Mississippi was under the gun on Tuesday with several reported tornado touch downs as a line of severe storms moved through.

Most of the damage was to trees, but some structures were impacted, including a church.

Now they are under a winter storm watch and could see up to 3 inches of snow by Thursday night!

The Jackson weather office has placed that region under a Winter Storm Watch in case the snow materializes.

Several homes were damaged as a tornado moved through the Alexandria vicinity in Louisiana.

This lastest storm system has brought down a lot of cold air form Alaska and Canada, and that translated into some good snows for many locations.

Check out the latest US Snow Cover map.

As you can see, many states including most all of Canada has snow on the ground.

Speaking of Canada, I got the nicest comment left on the blog from someone up there yesterday. If you are reading today, I just want to say thank you.

Be Your Own Forecaster

I've had a few people write me recently asking what forecast models I look at to predict the weather, and which models are the best this time of the year.

Both are hard questions to answer.

Models all tend to have their own quirks, and some do better than others when it comes to a particular type of weather pattern.

They also tend to vary by location -- with most all models having a tough time in places like Colorado due to the varied terrain.

Still, they help give an overall idea of what might happen on the larger scale, and then it's up to the forecaster to fill in the details here at home.

I have a variety of places I like to go on the web to look at data.

First, I like to check the climate prediction center. Click here for the CPC. In particular, I look at the 6-10 day outlook and the national US hazards forecast.

Now if you aren't too savvy on reading forecast models on your own, then one thing you can do is to read the local forecast discussion from your local National Weather Service forecast office.

Essentially, they are reading all the models, both long and short-term, then writing a discussion of what they see, think and feel about the forecast.

The only problem is they will use some weather jargon that you may not be familiar with, such as FROPA.

FROPA is short for frontal passage.

Click here and you will get a US map. Click on your state and it will bring up a page showing your state and 10 options to click on.

One of those options is the forecast discussion.

If your state has more than 1 forecast office, just scroll through until you find the one from your area.

It is interesting to read surrounding offices though, because forecasters don't always agree on things.

If you want to do your own forecasting -- to get a feel on the forecast, first you need to look at the regional snapshot of what is happening in terms of wind, temps, and precipitation. Click here and when the page loads, click on surface -- then your region.

And finally, from the link I just put above, you can also click on forecast and get some of the more common weather models.

The RUC is a short-term model, the Eta is a medium-range model and the GFS is long-term.

When looking at the model, a good plot to look at is the 500 mb winds under the "aloft plots" section.

This will show you what is happening with weather patterns at approx. 22,000 feet -- which is free and clear of all forces that impact weather, such as high mountains.

Major Winter Storm Looming?

I was looking at the 180 hour computer forecast models this morning and one of them paints a pretty potent winter storm late next week sweeping from Colorado and New Mexico, east across the Tennessee and lower Mississippi River valleys.

It would also bring down a good dose of arctic air that would cover much of the eastern US, with the core of the cold around the Great Lakes.

It's just a computer model and can change outputs several times between now and then, but it still is worth watching.

Under a fresh snowpack, Denver dropped to 5 below zero late Thursday night, and that tied our record low last set in 1909.

If you are traveling today, anticipate more lake effect snows around the Great Lakes states.

It will be windy and near whiteout conditions today across southeast Wyoming.

The biggest weather story is the cool air. Almost everyone east of the Rocky Mountains will see afternoon highs no higher than the 40s.

The immediate Gulf Coast will see highs only in the 50s, including Houston and New Orleans.

If you need a little warmth, head to south Florida or southern California and southern Arizona where you will find 70s and even a few 80s, particularly in Florida.

Hurricane Sesaon Ends, Records Set

The 2008 Atlantic Hurricane Season ended on Sunday with some new records established, including the longest lived July tropical system in the Atlantic basin (Bertha) at 17 days.

Click here to read a complete season summary written by the National Hurricane Center.

Meanwhile, it continues to be an early winter for much of the US east of the Rockies. A large trough of low pressure is keeping the area under a northwest flow, sending waves a cold air down from Canada.

Places in the southeast like Nashville and Atlanta have been seeing conditions more prone to January over the past several days.

They've even seen some snow!

Click here and check out the interactive US snow cover map.

Snow is on the ground from northwest Arkansas to Michigan.

Much of Illinois, Indiana and Missouri have snow on the ground.

All of Wisconsin and Michigan have snow cover.

It is important for a forecaster to look at the extent of snow cover because it can greatly impact the weather.

If northwest winds are blowing across that huge area of snow cover, it could mean locations downwind will be colder than computer forecast models indicate.

You also have to consider snow depth.

In many of these locations, there is snow on the ground but it isn't very deep -- at lower latitudes where the sun angle is a bit higher.

Therefore it will melt quicker than locations immediately off the Great Lakes...so it may or may not have such a large impact on the regional weather.

Just another consideration a forecaster must take into account when working on the daily forecast.

This is one reason why we ask you to report a daily snow depth on your CoCoRaHS report.

Even if there is no precipitation and no new snowfall, you very well may have several days where both of those fields on your report are ZERO, but there is a total in the daily snow depth column.

It gives a history of what is happening at your station regarding the overall, large scale weather pattern.

The data can be very helpful to both a forecaster or a researcher.

Hurricane Season Coming To Close, New Record Set

Here is a great article about the 2008 Atlantic Hurricane Season, which ends on November 30.

Click here for article.

You may have to scroll down the page a little to see the article once it opens.

Happy Thanksgiving!

Thank you so much for all you do for CoCoRaHS!

When you take a look at the daily US maps and see all the data points, it really makes you feel proud to be part of such a cool organization with so many great people!

Unsettled In New England, Hurricane Force Winds On Mt. Washington

Well they say some of the worst weather in the world happens on Mt. Washington!

Look at the live weather conditions from 11:30 am Tuesday!



A sustained wind of 86 MPH gusting to 109! And the air temperature is only 20 degrees!

Wow can you imagine?!?

Elsewhere in New England that windy, but it is cold, unsettled and blustery.

Heavy rain is falling at the coast and in lower valleys, while moderate to heavy snow is falling in the mountains!

Wrapping Up Fronts

There is another type of cold front sometimes mentioned during the weather report -- and that is the "back door" cold front.

It's no different than a typical cold front except it moves in from the east or northeast, where as most cold fronts approach from the north or northwest.

It can happen anywhere, but is most common on a large scale in the New England states.

On a smaller scale, we get a lot of back door cold fronts along the eastern side of the mountains here in Colorado.

Cold air from Nebraska will pool and spill down the South Platte River Valley and into the Denver/Front Range area.

We had that happen this week in fact!

When a back door cold front moves into the New England states, often the cold air hits the Appalachian Mountains and can't go any further.

This is because cold air is heavy and dense, and it can't rise up and over high barriers like a mountain range.

We call this cold air damming.

So the cold front stalls along the mountains (cold air damming) and will actually become a stationary front since it stops moving.

Back door cold fronts combined with the terrain barrier make for tricky forecasts -- because you just don't know how much "umph" the front will have to make it up and over the mountain barrier.

Quiet For Most, And Some New Weather Lingo

Well it continues to be quiet for most today.

Heavy snows continue around favored areas of the Great Lakes. Winds continue to blow from a northerly direction over the warm, open waters -- picking up tons of moisture and dropping it in the form of snow at and just inland from the lakeshore on the south side.

Below normal temps continue in the southeast and will persist into the weekend.

And here in Denver, we dropped from the upper 70s to the 30s over the past 48 hours, and now we have a little light snow/freezing drizzle.

A new storm moving into the northwest will bring unsettled weather to Seattle and Portland to round-out the work week.

Here are some new weather terms to throw out at your next dinner party.

When a cold front weakens and the temperature gradient weakens (meaning with distance, the difference in temperature becomes less drastic) -- you call that frontolysis.

And when you have the opposite, and the temperature gradient strengthens, meaning the front and associated storm system (low pressure) is growing stronger, it is called frontogensis.

Quiet For Most, Now Let's Find That Cold Front

It's a quiet weather day for much of the country.

More heavy lake effect snow is expected today and over the next few days across portions of Michigan.

Marquette looks to pick up another 6-18 inches of snow depending on where you live in that region.

The terrain and exact orientation of the wind off the lake can bring a foot of snow to one spot and just an inch or two down to another.

Jacksonville, FL set a new record low last night of 28 degrees.

Denver set 2 new records on Tuesday. One was a high of 78 degrees. The other was the overnight low, which was only 47. That is a new record high low temperature for the date.



The map above will be very hard to read but I want to use it for today's lesson about cold fronts.

I believe the picture will get bigger if you click on it.

So if you were to take a weather analysis class, this is an exercise you would likely have.

It's called find and draw the cold front! This map is showing surface observations at major reporting stations around the US for 8 am Wednesday, Nov. 19.

It shows different weather parameters for each location, including temperature, dewpoint, wind direction and speed.

Actually reading and decoding the observation could be another entire lesson within itself, and we may do that at some point if there is any interest.

So if a meteorologist had this map, to find the cold front, he or she would...

Look for sharp temperature changes over a short distance (such as the pocket of 40s and 50s over southern Kansas versus the 30s not too far to the north over Nebraska, Iowa and points north.

Changes in moisture (or dewpoint)-- which is much harder on the map I provided you because much of the country is under a dry air mass. It's much easier to find a cold front using dewpoints in the warm season.

Shifts in wind direction -- look from Texas up to Kansas, winds are blowing from the south. But above that in to Nebraska and Iowa northward, winds are coming in from the north.

You can also look at pressure and pressure changes if you have maps that span a few hours, or you can also look at the clouds and precipitation patterns.

So just in taking a quick glance at the surface map above from this morning, simply by checking the temperatures and wind, we could porbably draw in a cold front somewhere in the central plains states, likely across southern Nebraska and extending toward Michigan on the east and the Rockies on the west.

Who knew finding the cold front could be so much fun!

Now I should say if we pull a surface map from mid to late afternoon, it could be much easier to spot the cold front -- because we will be at maximum daytime heating and the atmosphere will be completely stirred up.


The problem with the 8 am map above is overnight the atmosphere mixes out and settles down with no sunshine to act as the "oven burner" to cook things up.

So although we clearly get an idea something is happening in the Nebraska/Iowa vicinity from the 8 am map above, if we looked at a 3 pm map this afternoon, the front may be a little more obvious.

Then again -- it may not be any more clear than the map above.

This front isn't terribly dynamic, meaning there is already some cool air in place over much of the country, so the clash of the air mass in front of and behind the cold front isn't as dramatic as it could be -- so the afternoon map may not be more obvious than the one above.

That is why people get into weather -- it is always different from day to day, hour to hour and in many cases minute by minute.

You just never know -- and you can never say for sure because there are so many variables involved that can shift ever so slightly and make all the difference in the world to the outcome.

From Frosty Florida To Cookin' Colorado

The lake effect snow machine has been cranking the past few days and a strong northwest flow of cold air pours out of Canada.

Some places have picked up 1 to 2 feet in the favored area between Cleveland and Buffalo, as well as in portions of Michigan.

Some flakes have been seen as far south as the Smoky Mountains of eastern Tennessee and western North Carolina.

So while Denver is expected to set a new record high today, and possibly for the entire month, southern Georgia and much of northern Florida is bracing for overnight lows in the mid to upper 20s tonight.

Over the past few days we've been discussing fronts. It's time to talk about the cold front.

I found a great picture snapped as a cold front moved through the Memphis, Tennessee area.

Click here to check it out.



The cold front is the dividing line between a cold, dry and stable air mass versus one that is warmer, more moist and less stable.

It is drawn as a solid blue line with the triangles pointing in the direction the front is traveling.

Tomorrow we'll chat more about cold fronts.

Snowy Around The Lakes; More About Fronts

Well if you want winter, head to the Great Lakes!

A strong northwest flow is creating pockets of heavy lake effect snow today along the southern and eastern shores of all 5 lakes.

Some places, especially in the upper peninsula of Michigan, could see 6-12 inches of the white stuff.

Meanwhile here in the west we are having round 2 of Indian Summer, with Denver expecting upper 60s to mid 70s over the next couple of days.

Ok on Friday we talked about the stationary cold front.

The type of weather one would see along this type of front actually depends on the type of air mass on either side.

Sometimes the weather along a stationary cold front is clear to partly cloudy and dry, with much colder air behind it.

This happens when the air mass on either side of the front is dry.

Other times, warm moist air may ride up and over the cold dry air, bringing widespread clouds and precip to a large area.

An example of this: say you drive from Chicago to Milwaukee in clouds, drizzle and fog and experience a temperature of 45 in Milwaukee and 71 in Chicago.

Once either of the two air masses begin to move, the stationary front will get erased off the weather map and either a cold or warm front will be drawn.

It just depends on which air mass wins out.

Weather Fronts -- More Than You May Want To Know

Well we've been discussing air masses over the past few blogs, and yesterday I told you a front is the "front-line" so to speak of these air masses.

Today we'll start learning more about fronts.

Cold fronts, stationary fronts, warm fronts, back door cold fronts, occluded fronts...you may have never realized there are so many terms out there.

It all just depends on what is happening at the boundary between two air masses.

Let's start with a stationary front.




This is just a front that has no movement. Neither air mass is strong enough to overtake the other.

Waves of lower pressure, or disturbances, may ride along the front bringing unsettled weather to a region, sometimes for several days.

Eventually either the two air masse kind of just equal out and blend into one another, sometimes described by a t.v. weatherman as the front "washing out".

Or other times a new weather system may come along and give one air mass the strength it needs to push on and win the battle.

On a colored weather map, the stationary front is drawn as an alternating red and blue line.

The semicircles point toward the colder air on the red line.

The triangles point toward the warmer air on the blue line.

(Kind of opposite of what one might think -- welcome to meteorology!!)


Winds at the surface tend to blow parallel to the stationary front, and in opposite direction on either side of it.

Up above in the atmosphere, winds also tend to blow parallel to the front.

(Remember you now have to think 3-D -- the cold front extends from the surface up into the atmosphere)

Monday we will talk about the types of weather you can expect along a stationary front.

The 3-Dimensional Front

Over the past few days we have talked extensively about air masses.

The leading edge of these air masses are often where you find a front.

A front is simply a transition zone between two different air masses.

More specifically, it is a transition zone between air masses with different densities.

And since density differs between hot and cold air, we are talking air masses with different temperatures.

Along with temperature, we often find a difference in moisture too.

Now here is where things can get tricky. To wrap your brain around a full degree in meteorology, you eventually reach a point in the coursework where you have to start thinking in 3-D.

So picture in your mind a big, cold air mass moving south from Canada.

On the weather map you see on television, the leading edge of this air mass will be noted by a cold front.

So now pretend you are standing in your yard looking north and you can actually see this cold front moving toward you, evident by the line of clouds and sometimes by the dust the winds kick up out ahead of it.

Once it reaches you, look up -- the cold front also extends up into the atmosphere.

This is why you have to picture weather in 3-D.

This upward extension of the cold front is called a frontal surface, or frontal zone.

The frontal system not only extends out horizontally along the surface, but also vertically up into the sky.

Tomorrow we'll talk more about different types of fronts.

Maritime Polar Air Masses

During the winter, cP (Continental Polar) air masses move east-southeast from Asia over the Pacific Ocean around the Aleutian low.

The ocean water modifies this air mass by adding warmth and moisture to it.

It gradually transitions from a cP air mass into a mP air mass.

By the time it reaches the USA, it is cool, moist and unstable.

You often hear the television weather folks call this a warm storm, and it usually brings a lot of rain to the Pacific Northwest with some high mountain snow.

We can see mP air masses move into the New England states off the North Atlantic, but it isn't nearly as common due to the westerly winds that prevail up at the jet stream level.

Maritime Tropical Air Masses (mT) originate from the tropics and move across oceans toward land.

The best example of this is the "Pineapple Express" -- which is a flow of moisture from Hawaii toward the west coast of the US.

This flow of moisture can be really powerful -- with the best example coming from January 1997.

The "pineapple express" slammed central and northern California with tremendous flooding that sent thousands running for higher ground.

Yosemite National Park was closed for 2 months due to flood damage after the storm event.

In the eastern US, maritime tropical air masses that impact the weather mostly originate over the Gulf of Mexico or the Carribbean Sea.

Finally, we have Continental Tropical Air Masses and these originate in the deserts of the southwestern US and northern Mexico.

This is when we see an area of high pressure bring several days of 100+ degree heat to the center of the country, typically in late June to early August.

Air Masses And Your Weather

Here in the lower 48 states of America, we typically see a few different types of air masses impact our weather.

cP (Continental Polar) often visit during the winter. This air mass is sometimes called cA (Continental Arctic).

They usually bring bitterly cold weather.

These air masses originate over the ice and snow covered regions of northern Canada, Alaska and sometimes even Siberia.

Once an air mass slides south along the Rockies and enters the plains, there are no barriers to stop it -- so it moves all the way to the Gulf of Mexico.

Sometimes this is called a Texas norther.

Cumulus clouds are rare -- even during the warmest, most unstable part of the day -- because these air masses are dry.

At night, with clear skies and light winds, temperatures drop like a rock.

These air masses can make heavy snow when they move over a warm, large body of water, such as the Great Salt Lake or the Great Lakes.

These snow bands are common on the eastern shores typically when a large cP or cA air mass moves south and into the USA.

The Rockies, Sierra Nevada and Cascade mountain ranges usually protect much of the west coast from these bitterly cold air masses.

But if the right weather pattern sets up, they too can see the frigid air.

One very memorable arctic outbreak in the US took place between December 21-24, 1989. There were over 350 record lows set east of the Rockies.

$480 million dollars of damage was done to crops in Florida and Texas.

That same week in 1990, a bitterly cold air mass settled into the west, causing over $300 million dollars of damage to crops in California.

Lows dropped into the 20s all the down into the Los Angeles region. It was the coldest weather in over 50 years.

During the summer we look forward to seeing a large cP air mass move south out of Canada because they cool us down and lower the humidity for a few days.

Tomorrow we'll talk about maritime polar air masses. (mP)

More About Air Masses

In my post last Tuesday, we talked about where air masses originate and 4 different classifications.

They were cP, cT, mP, and mT.

If you ever do any additional reading or want to "study-up" a little more on the subject, let me introduce two more letters you may find in the classification.

k

w

If the air mass is colder than the surface it's over, the lowercase letter "k" is added.

Just think of "k" meaning cold.

And if the air mass is warmer than the surface below, the lowercase letter "w" is added.

So adding this 3rd classification, you could potentially see an air mass described as cPk.

That would be an air mass of continental (c) polar air (P) that is colder than the surface below it (k).

I know, I know -- for some it may make sense and others it may have went right over your head.

If the latter describes you, don't worry...

When I was in meteorology school I could not wrap my brain around this concept to save my life!

Now I totally get it.

Unless you have taken a meteorology class, until reading this blog, you may have never heard of the concept where one can identify air masses based on origin and their temperature/moisture characteristics.

Or have you?

There are a lot of "nicknames" that describe some of these types of air masses...and they are often said by meteorologists on television.

Arctic Express or Siberian Express -- a large, bitterly cold and typically dry air mass that moves down from Siberia and into the lower 48 states during mid-winter. Well since this is an air mass that forms over land (Sibera) it is "continental (c)" and Siberia is located in a polar region (P) and depending on how far south if travels, it will either be colder or warmer than the surface it is above -- so let's assume colder (k). So this air mass is a "cPk" air mass.

Pineapple Express -- when a flow of air that feeds into the west coast of the US directly from Hawaii and brings ample moisture. Since it forms over an ocean (m) and is from a tropical location (T), it would be an air mass labeled "mT" -- and then if the air is warmer than the surface below, you would add "w" and if cooler "k". So this air mass would be either "mTk" or "mTw".

We'll chat more tomorrow!

Back From Trip, Lots To Talk About

Well I am home from my business trip -- had to work in Salt Lake City for a few days.

We still have not seen our first flakes of snow in Denver (at the official reporting station).

A few higher suburbs have -- including my house -- but it doesn't count until a trace or more of snow falls at Denver's snow measurement site.

Salt Lake City, however, has seen it's first significant snow of the season -- I landed during a snow band off the lake and drove in it all day Wednesday.

I had no idea they could see "lake-effect" snowfalls -- much like they do in the Great Lakes.

Portions of the region were even under lake-effect snow warnings.

As I drove from the airport south toward Sandy, the snow really picked up in intensity.

And speaking of snow, my goodness -- the upper plains got whalloped this past week, esp. the Dakotas!

I didn't get much time to follow the news story due to work, but have enjoyed seeing all the online reports.

And the 2008 Atlantic Hurricane Season just doesn't wanna give up as Paloma churns across Cuba.

The storm is weakening from major hurricane status, and is now a tropical storm.

The remnant low is expected to linger off the coast of northern Cuba this week.

That could mean unsettled weather for south Florida and the Bahamas.

And if you haven't seen an episode of "Storm Chasers" on the Discovery Channel, check it out tonight at 10 pm ET/PT.

I caught an episode on my flight back to Denver the other night. (That is why I fly Frontier, for the Direct TV at every seat!!)

It is action packed and at times will have you sitting on the edge of your seat.

Where Do Air Masses Originate?

There are basically 2 source regions for where air masses form, but 4 general categories to classify the source of an air mass.

First, the two main source regions, each defined with a capital letter...

P -- air masses that originate in Polar latitudes

T -- ones that have warm Tropical origins

Now the 4 general categories to classify an air mass.

If the source region is over land, it will have a small letter "c" before the initial. If it is over water, there will be a small letter "m" before the main source region initial.

cP -- cold, dry and stable air throughout the air mass

cT -- hot, dry, stable air aloft with unstable air at the surface

mP -- cool, moist and unstable air throughout the air mass

mT -- warm, moist and usually unstable air found throughout the air mass

There are a few other classifications, such as cA (continental Arctic air masses) but if you master the 4 main ones above you are in business!

I am traveling on business out of state the next few days and will not have access to a computer.

BUT -- when I return I will pick up with the air masses of North America in more detail.

Get out and vote -- your voice could be the deciding one!

Happy Election Day!

Air Masses and Fronts

I got away from the "daily lesson" in recent weeks just due to a hectic work life, but will attempt to get back in the grove.

This week we're gonna talk about air masses and fronts.

An air mass is an extremely large body of air where the temperature and humidity are similar as you increase with height or travel across the air mass.

So let's take a large, winter air mass that moves down from Canada across the lower 48 states.

It may have highs of -15 in Minneapolis with a dew point of -18, and in Little Rock it may have a high of +10 with a dew point of +7.

Although those temperatures are not similar as you travel the 1,000 miles across the air mass, both are very cold and very dry for the respected locations, and would be associated with the same air mass.

Now suppose Minneapolis is still -15 with a dewpoint of -18, but Little Rock has a high of 45 and a dew point of 38 -- the two locations would not be under the influence of the same air mass.

Minneapolis would be very cold and very dry while Little Rock would be cool but moist in that scenario.

Air masses originate in what we call source regions.

These are places that are typically flat, have light surface winds and a uniform topography and other characteristics -- i.e. deserts, the frozen arctic

Here in the much of the lower 48 where we live (also known as the middle latitudes (between 30 and 60°N on the globe) -- most locations are not good source regions because surface temperatures and moisture characteristics vary considerably.

We live in what is known as a transition region -- a zone where air masses with different physical properties move in, clash, and produce an exciting gamma of weather.

Tomorrow we will talk about the classification of air masses.

Will November Be As Quiet As October?

All in all, October was really a quiet weather month for the entire country.

We had a few strong cold fronts move through that brought a taste of what is to come.

There was some October snow, mostly in either the northern Rockies or New England.

We also saw just a little bit of severe weather in the central states, but nothing like what some October's have brought.

So what does this mean? Will the bottom drop out as we head into November?

It's anybody's guess -- but I can tell you we will see the weather pattern become a little more active, at least for the northwest and northern tier of states over the next 5-7 days.

The current national hazard outlook is calling for heavy rain and snow across eastern Wyoming, Montana, and the Dakotas around the middle of next week.

Heavy rain is also forecast for the Pacific Northwest.

This will all be courtesy of a few storm systems moving in from the Pacific.

I know here in the Denver area, November is typically our cloudiest month of the year as we see frequent storm systems moving across the state this time of year.

It will be fun to watch and see how all this plays out.

If you have a thought or opinion on the subject, feel free to leave a comment for everyone to see.

Interesting Weather Facts

I am such a nerd when it comes to trivia and weather facts.

I'd vote we should call Game Show Network and get a weather jeopardy game show
on the docket!

Just teasing!

I was surfing for weather facts the other day and come across this web site.

Click Here.

I am not sure who maintains this site and where the data came from, but it was very neatly compiled and fun to read.

Enjoy.

Cooling Down

Last night was a chilly night for many across the central and southern plains.

Numerous states along the Mississippi and Ohio Rivers were under either frost or freeze advisories.

The National Weather Service issues these when temperatures will be cold enough to harm tender vegetation.

A frost advisory means to protect tender plants while the temperature flirts with freezing for a few hours.

A freeze advisory means a hard freeze is expected (usually at or below 28° for 4 to 6 hours) and that the growing season will be over.

The weather is extremely quite around the nation right now with no huge storms expected this week.

A northwest flow of wind over the open waters of the Great Lakes will keep some lake effect snow showers in the forecast over the next few days in that part of the world.

History Of Daylight Savings

Well we are just a few days away from Daylight Savings ending -- November 2.

I pulled the following info off the US Naval Observatory website. I thought it would make for interesting reading for you.

Here is the link or you can read the info below.

Standard time zones were instituted in the U.S. and Canada by the railroads in 1883, but were not established into U.S. law until the Act of March 19, 1918, sometimes called the Standard Time Act.

The act also established daylight saving time, a contentious idea then.

Daylight saving time was repealed in 1919, but standard time in time zones remained in law. Daylight time became a local matter.

It was re-established nationally early in World War II, and was continuously observed from 9 February 1942 to 30 September 1945. After the war its use varied among states and localities.

The Uniform Time Act of 1966 provided standardization in the dates of beginning and end of daylight time in the U.S. but allowed for local exemptions from its observance.

The act provided that daylight time begin on the last Sunday in April and end on the last Sunday in October, with the changeover to occur at 2 a.m. local time.

During the "energy crisis" years, Congress enacted earlier starting dates for daylight time.

In 1974, daylight time began on 6 January and in 1975 it began on 23 February. After those two years the starting date reverted back to the last Sunday in April.

In 1986, a law was passed that shifted the starting date of daylight time to the first Sunday in April, beginning in 1987. The ending date of daylight time was not subject to such changes, and remained the last Sunday in October.

The Energy Policy Act of 2005 changed both the starting and ending dates. Beginning in 2007, daylight time starts on the second Sunday in March and ends on the first Sunday in November.

First Flakes Of The Season

I pulled into my garage last night around 10:30 and said was that a snow flurry?

And sure enough, by 10:35 or so, it was lightly snowing.

I went to bed around 1 am and had a dusting on the ground, but it was gone by 8 am when I got up.

Talk about exciting!!! Bring on the winter season, homemade stew and chili!!!

Severe weather broke out as expected across extreme eastern Colorado, SW Kansas and the panhandles of Texas and Oklahoma on Tuesday.

Large hail fell around Garden City, KS and strong winds were reported in Buffalo, OK.

Today, some severe weather is still possible around the Ark-la-tex.

Speaking of hail, it is a form of precipitation that is probably the least documented but one we want to know the most about.

Hail forms when supercooled water droplets (that means the drop of water is below freezing but doesn't turn into a solid) freezes when contacting condensation nuclei.

A condensation nuclei is something like a dust particle.

Once this happens the updraft from the storm carries the newly formed hail stone up and down in the cloud.

With each cycle of going up and down, more supercooled water droplets freeze instantly on contact with the former condensation nuclei (now hailstone) and it grows.

The longer this process repeats the bigger the hail will get.

Once the weight of the hailstone overcomes the strength of the updraft, it falls to the earth.

If you cut a hailstone in half, you can actually see the layers of growth it went through in the cloud.

Another Winter Storm Set To Roll By

A cold front moved through the Denver area Monday evening.

While driving to my part-time job I saw several huge bolts of lightning.

One was right in front of me as I barreled down I-70 at 70 mph -- it made me see spots it was so close and bright.

Interestingly enough, I never heard thunder. But I talked to several people who did.

The cold front may trigger a little bit of severe weather on Tuesday over western Kansas, extreme eastern Colorado and the panhandles of Oklahoma and Texas.

The threat for severe weather will shift southeast toward the Ark-la-tex by Wednesday. (Ark-la-tex is where Arkansas, Louisiana and Texas join together) Also know as the Red River Valley.

On the cold side of the storm, there will be a rain-snow mix from extreme northeast Colorado up through western Nebraska and the central Dakotas.

1 year ago this week we saw one of the worst tornado outbreaks ever in the month of October with dozens of twisters touching down between October 17-19, 2007 -- from lower Michigan to the Gulf Coast.

One of the worst twisters was an EF-3 that struck Nappanee, Indiana.

Storm Chasers Returns To Discovery Channel

If you like storm chasing, then you will want to watch Discovery Channel this Sunday (Oct. 19) at 10 pm for the debut of Storm Chasers, Season II.

Discovery Channel returns to the heart of “Tornado Alley” for a firsthand look at one of nature’s most destructive forces in an all new season of STORM CHASERS, premiering Sunday, October 19, 2008, at 10 PM (ET/PT).

Click here for a preview.

Veteran research meteorologist Dr. Joshua Wurman and filmmaker Sean Casey go head to head, toe to toe and fender to fender with newbie chaser Reed Timmer racing to capture rare footage and valuable scientific data.

Last season, Casey’s tank-like TIV or Tornado Intercept Vehicle, raised eyebrows roaring down the nation’s highways and byways looking for the shot of all time – filming from inside a tornado.

Now, his new and improved creation, the TIV-2, raises the stakes, providing the astonishing footage and the terrifying excitement of storm chasing.

Water-Logged Kansas And Some Weather History

The city of Wichita, Kansas broke their annual precipitation record on Wednesday with the latest total since January 1 sitting at just over 50.00 inches!!

50.49" to be exact.

Can you believe that? When I grew up in Arkansas I could, but after living so long in Colorado, it's hard to imagine.

Denver is essentially a high-desert as many of you know, and we are lucky if we get our annual average of just over 15" per year.

With every drop that falls (either rain or snow) between now and December 31, the new annual precipitation record for Wichita will just continue to be rewritten.


And here is a little weather history I saw on the wire from the Goodland, Kansas office of the National Weather Service.

I thought it was interesting.

IN 1860...THADDEUS HYATT...PRESIDENT OF THE NATIONAL KANSAS
COMMITTEE...WROTE A LETTER TO THE PRESIDENT OF THE UNITED STATES
IN AN EFFORT TO OBTAIN ASSISTANCE FOR THE SUFFERING INHABITANTS OF
KANSAS. HE DESCRIBED IN DETAIL THE NEEDS OF THE
SETTLERS...INCLUDING THEIR LACK OF ADEQUATE WINTER CLOTHING AND THE
SCARCITY OF FOOD. ACCORDING TO HIS PERSONAL OBSERVATIONS...HYATT
CONCLUDED THAT THE ONLY OPTIONS LEFT TO KANSAS SETTLERS WERE EXODUS
OR STARVATION. THE SETTLERS WERE SUFFERING FROM A PARTICULARLY
SEVERE DROUGHT IN 1860.

Tropics Heating Up, But No Threat To U.S.

After a few busy days without much internet or tv time, I was almost shocked when I logged into the National Hurricane Center's website this morning.

Tropical Storm Omar sitting southwest of Puerto Rico, Nana way out in the Atlantic and Tropical Depression #16 way down near Central America.

The good news is none of these storms will impact the US mainland or even come close.

Omar is expected to strengthen into a hurricane and it tracks northeast, very close to Puerto Rico, and then out to sea over the coming days.

Meanwhile the first major winter storm of the season here in the west has moved on. No snow in the immediate Denver area, but we did have our first hard freeze AND an entire weekend with cold, fog and drizzle.

Snow was measured in feet across portions of Wyoming and Montana over the weekend.

Hurricane Norbert To Make Baja Landfall

It has been 30 years since a hurricane made landfall on the Baja of California during the month of October.

The last was Hurricane Pauline on October 2, 1968.

There have been a handful of tropical storms that made landfall during October.

So this is a pretty rare event.

Norbert should move onshore sometime early Saturday before the noon hour.

Meanwhile a second system is moving northwest, parallel to the Mexican coastline. This is Tropical Storm Odile.

Odile may briefly gain hurricane status in the next 48 hours.

First Major Winter Storm Of Season Looms

A potent winter storm will impact portions of the west over the weekend -- and for some it will be the first major storm system of the year.

It could also quite possibly become a very memorable storm system.

The southern half of Montana and the northern half of Wyoming could see historical snowfall totals, with periods of snow starting as early as tonight and lasting through Sunday.

Some of the highest elevations and locations on favored slopes could see up to 2 feet of snow, which for this time of year is pretty significant.

It will also be a heavy, wet snow -- and with many trees still leafed out, that snow could cause a lot of damage.

We are still potentially facing the first snow of the season here in Denver too over the weekend.

Anything greater than a TRACE of snow is considered measurable and would count as the season's first snowfall.

Severe weather is in progress this morning across portions of Florida, SE Georgia and coastal S. Carolina.

In fact, while writing this blog I see a tornado warning has been posted for locations around Fargo, Georgia.

Get ready for a BEAUTIFUL weekend in New England with ample sunshine.

Frost, Freeze, and Winterization

The Front Range of Colorado was under a frost advisory this morning and most of us woke up with temperatures between 35 and 40 degrees.

Not everyone saw frost -- but as a precaution we were placed under the frost advisory.

Visible white frost forms on cold, clear, calm mornings when the dew-point temperature is at or below freezing.

When the air temperature cools to match the dew point, now called the frost point when specifically trying to forecast for frost, water vapor in the air changes directly to ice without becoming a liquid first -- a process called deposition.

These delicate, white crystals of ice are called hoarfrost, white frost, or simply frost.

Frost has a treelike branching pattern that easily distinguishes it from the nearly spherical beads of frozen dew that can sometimes occur.

In dry climates such as here in the west, the air temperature can rapidly drop below freezing without the process of frost ever happening -- this is called a freeze, or sometimes a black frost, because it can be so damaging to crops.

So for those in the colder climates who have not winterized your home, and especially irrigation systems, it is definitely time to do so.

I would make plans to turn the water off and have the sprinklers blown out sometime within the next 1 to at most 3 weeks.

One important note for CoCoRaHS observers -- frost and dew are not precipitation. These processes are taking place at the ground due to physical processes involving temperature and water vapor.

Precipitation as you know takes place up at cloud level and falls to the ground.

It is good, however, to note things like dew and frost in your comments because it does help "paint the picture" of what was happening weather-wise that day at your station.

For example, if you have zero precip but stated it was a frost covered morning -- I know it was clear and calm at your house. The dew-point was probably between about 29-32 and the air temperature was similar long enough for frost to form.

Severe Thunderstorms Possible Today

There is a slight risk for a few severe thunderstorms today across eastern Oklahoma, SW Missouri, NE Texas and western Arkansas.

A cold front is pressing across the center of the nation with rain extending from Canada to Texas.

It is a narrow band of rain associated with the cold front.

An area of low pressure, along with the cold front and some warm, moist air will be the mechanism for kicking off the isolated severe weather today in the southern plains.

Much of the west is sitting sunny and dry but a new storm system building over the Pacific will bring more unsettled weather to the west by the coming weekend.

Here in Colorado the lower elevations saw a chilly rain on Sunday. Enough snow fell in the mountains to close a portion of the highest paved US highway in America.

Trail Ridge Road (US 34) which connects Estes Park to Grand Lake, passing through Rocky Mountain National Park, will likely remain closed for the rest of the season.

It is typically open from Memorial Day until the first significant snow of of autumn.

They are dropping well below freezing now above the timber line (11,000 feet) so that snow will start piling up with each passing storm system up there.

If you've never been here to drive it, you have to come visit next summer! I was up there 2 weeks ago to see the elk and the fall color.

As a bonus I also saw 4 moose!

If you want some snow, and can get away this week, head to Fairbanks, Alaska. This week's forecast calls for highs near 30 and lows around 20 with occasional snow showers possible.

Pacific Storm Moving On Shore

A large storm system is moving across the western US today and it will bring the most widespread taste of autumn so far this season.

Most of the intermountain west will see rain and even snow showers over the weekend with highs only in the 50s and 60s with lows in the 20s and 30s.

It's even been frosty around the Great Lakes states the past few mornings!

I love this time of year.

Today I mowed the yard, shut down the sprinkler systems and did some other "winterizing" chores.

Welcome Lucy Lu! She is my new basset that I adopted this weekend so my boy basset (Samson) would have some companionship.

I am also babysitting Sierra (also a basset) so it is nothing but puppy love around here.

As I worked in the yard they ran their little hearts out. Now all 3 are stretched out in the living room taking a lunchtime nap.

Trough Building Over Pacific

A trough of low pressure and a pool of colder air is building over the Pacific Ocean today.

Winter weather advisories cover much of east-central and southeast Alaska, including Fairbanks and areas east of Anchorage.

By early next week we should see the first signs of this cooler air sweeping across the lower 48.

Denver will see highs drop from around 80 this week to just above 60 next week, and our overnight lows are forecasted to dip into the mid and upper 30s.

Some locations closer to Canada have already seen some chilly weather. In fact, central Wisconsin (north of Madison) is currently under a frost advisory for lows dropping into the 29-32° range tonight.

A frost advisory is issued when temps may drop into the upper 20s and lower 30s briefly, but not long enough to end the growing season.

A freeze advisory is issued when temps are expected to drop below 29 degrees for several hours, putting an end to the growing season.

What Will October Bring?

This can be a fun month if you like changing weather.

Here in Denver, we usually start out with 70s and lower 80s, see our first freeze by the 7th or 8th and our first snow by the 19th.

Highs usually are only in the 40s and 50s by Halloween.

We've had some Octobers that were high and dry and warm, and some that were cold and snowy.

A lot of people remember the blizzard of 1997 in Denver.

If it does snow this month, it is usually a wet and heavy snowfall with a lot of moisture content.

So what about where you live?

It is a transitional month for much of the country.

We usually see a small spike in severe weather across the midwest and the south as cold fronts start moving south out of Canada and the clash of airmasses being, much like we see in the spring.

Fall's Finest For Now

Much of the country continues to experience quite and tranquil weather.

Days are still warm but nights tend to get a chill, which lets us know it is only a matter of time until some colder weather comes down from Canada.

Some colder air has built over portions of Alaska. As I write this blog, Fairbanks is sitting just above 20 degrees with fog.

Their rivers and lakes are still open which may contribute to additional dense fog.

That pocket of colder air will move south over the next few days, but by the time it reaches the lower 48 it will have modified significantly.

Overnight sub-tropical storm Laura developed in the central Atlantic. It will move north and then east, potentially approaching Britian.

Hurricane Watch Posted For Coastal Maine

Wow, something you don't see everyday.

Hurricane Kyle is steaming north across the western Atlantic and the latest forecast model projections have it possibly making landfall on the upper-east coast of Maine or slightly east of there in New Brunswick.

As a precaution, the National Hurricane Center has posted a watch for the eastern coast of Maine.

It will bare watching today and tomorrow to see exactly how this plays out.

We certainly would not be talking a major hurricane or even a strong hurricane like Ike, but nonetheless, some stormy times, with heavy rain and strong winds may lie ahead for this part of the world.

Watching The Tropics Once Again

The National Hurricane Center is busy watching two areas of disturbed weather today.

One has been absolutely soaking Puerto Rico and Hispanola over the past few days and will continue to do so for at least the next 18-36 hours.

Another is located much closer to home, off the coast of the Carolinas.

This isn't really a bad things as they still need plenty of moisture across the region.

Take a look at the latest drought monitor.

Elsewhere is it very quiet, but I bet it won't be too long before we see the first significant cold front of the season move south out of Canada.

It is that time of the year now!

Hail Cannons Create Stir in Vermont

There are several forms of weather modification, most notable probably being cloud seeding.

But another form of weather modification that some of you may have never heard of is the hail cannon.

We have several here in Colorado, esp. in the San Luis Valley growing region of south-central Colorado.

A hail cannon shoots off incredible sound into an approaching thunderstorm, and the shock wave is thought to disrupt the formation of hail, causing what would be hail to fall as slush or rain.

The device fires about every 4 seconds during the approach of a thunderstorm.

Hail cannons date back to the 18th century.

There is a lot of debate as to rather they really work or not, but farmers who have hail cannons swear by them.

I ran across the following article about hail cannons in Vermont, and how they have neighbors irritated.

Click here.

Happy Fall To You!

Well autumn is here, my favorite season of the year.

There is just something about the air each morning that I find so refreshing.

Fall arrived at 11:44 am eastern, 8:44 am Pacific.

I apologize for the quiet blog over the past few days. I've had a few projects going on that has kept me away from the computer.

I need to also cut today's short but hopefully I can get a full entry listed tomorrow.

Have a great one!

Chill Of An Early Fall

I am not talking about that old George Strait song, but about the cold weather on the way to New England.

Frost and freeze, yes freeze! -- advisories are in place for much of New England. I think several locations may wake up in the upper 20s and lower 30s tomorrow.

I was driving in the foothills west of Denver the other day and noticed color already showing up on some aspens. Even some places around the city have color on certain species of trees.

It is still hot out west in some places with wildfires burning in California and Oregon.

And the tropics remain quiet, which is a good thing!

Look at yesterday's CoCoRaHS national precip map on the front page. Pretty quiet!

That is common for this time of the year. There are no real widespread major weather makers on the map really. Just some small scale features.

That will change in the days and weeks to come as the sun angle continues to lower and cold air builds up north.

It will eventually break off and move south in the form of cold fronts, and interact with the warm air still over the southern US.

The result will be severe weather for some (the second seasonal peak in the mid-south) and winter storms for others.

It is an exciting time of year! I really love the fall weather and crisp air.

Here is a cool link to images of the Gulf Coast after Hurricane Ike. I came across this on the homepage of the NWS this morning.

Tropics Are Tranquil

What a beautiful image! Hopefully the season will quiet-down and we can get our coastlines cleaned up.

My was Ike ever a monster. I am sure that name will be retired soon if not already.

Hurricane names are retired if they cause a large amount of death and destruction.

Sadly, Ike lived up to both of those criteria.

Heavy Rains, Hurricane

Wow what a busy past 30 hours in the weather world. I had visitors in town with work and have been so out of touch.

So although I was dog tired after driving 600 miles in 4 days and working 14 Macy's stores, I stayed up until 5am watching the hurricane make landfall on tv.

It amazes me how much those reporters put on the line to get the story. I won't lie, I'd give my left leg to be one of those weather channel reporters! (okay not really, but you know what I mean)

Let's start with the non-hurricane rain.

Wichita, Chicago-land

Both the Wichita, Kansas and Chicago, Illinois metropolitan areas saw 6-12 inches of rain over the past 2 days.

We have a great network of CoCoRaHS observers in both locatons so you can check out the maps and see the precipitation footprint left behind by the storm.

The Wichita airport set a record rainfall on 9-12.

I heard one report that over 100 basements were flooded in the Chicago area from all the heavy rain.

Hurricane Ike

What do I say, it was amazing to watch and it is all over the news so I am sure you don't need me to write about it here in the blog.

My family is surrounded by tornado warnings even as I write this blog Saturday afternoon. They live in central Arkansas.

The storm made a direct hit on Galveston/Houston and hammered the entire coastline -- all the way into Louisiana.

I was just reading the local storm reports from Houston and the Tomball CoCoRaHS observer was called out with a foot of rain. (12.10" to be exact)

I talked with my 4 co-workers in the greater Houston area via text message and they all made it through, but all have damage to trees, roofs and/or fences.

Someone left me a message on Friday asking if I thought the hurricane had shifted slightly to the right.

I apologize for not getting that until today and for not being able to answer you.

As hurricanes near land, regardless of what forecast models show and try to predict, they wobble and can move erraticaly left to right.

Which is really tough because a small shift means someone gets in the eye and someone gets the brunt of the surge.

Did anyone watch Foxnews and Geraldo as he reported from the eye? Wow -- really something.

Forecasting is a difficult science, let alone forecasting a storm over water where there are no surface weather observations...but I have to say models and forecasters really had a handle on this storm.

Ike Eyes Houston, Galveston Vicinity

The Texas coastline is set to take a lashing from hurricane Ike. But the storm will be felt by thousands of people all across the region in just a few days.

If you haven't seen a recent map, the storm is huge! It's cloud shield covers much of the Gulf of Mexico.

Today's blog is short as I have an early meeting at work, but either tomorrow or over the weekend I will attempt to answer a few great questions I recently received.

Have a great day and if you are in the path of this hurricane along the Texas coastline, don't wait too long to make your storm action plans.

The latest forecast track from the National Hurricane Center has the storm coming on shore just a tad bit south of Galveston. That would put Houston, Galveston and the area bays in the right front quadrant -- where the highest and most dangerous storm surge will be.

This isn't good news -- especially since there is such a large population along the hurricane's path.

Blog Questions

An observer left the following questions yesterday so I will try to answer them as best I can.

Q. How many Traces of rain = an inch of rain?

A. Subjective so no answer. What I call a trace of rain may differ from what you call. Neither are actually measured in the gauge. Meaning the first line on the gauge is 0.01 inches. There isn't a "trace" line.

If I am out doing yardwork and a shower or strom approaches but barely misses me, and I feel about a dozen drops of rain and actually see the drop mark left on the sidewalk -- I would definitely call it a trace.

You might want to see the entire sidewalk and other surfaces completely wet before calling it a trace. Or since it "traced" so much, but still didn't quite measure in the gauge, you might go ahead and call that big trace a 1 hundredth of rain.

Does that make any sense?

So since a trace is not really measured, but interpreted, who knows how many equal an inch.

Personally, if that question were on an exam I would answer zero, then give a verbal explanation like I did above.

Q. Concerning hurricane Ike, are hurricane hunter planes allowed by Cuba, to over fly their country?

I found online that NOAA is the only federal agency with hurricane tracking capabilities that is authorized by Cuba to fly in its airspace.

Ike's Cuban Wrath

Hurricane Ike has given Cuba about the worst blow a storm could give, literally hammering the entire island nation coast to coast with high winds and surf and very heavy rain.

The good news for the US and the main population centers of the Gulf Coast is that it seems like with every model run the westerly storm track gets pushed further and further south.

Current thinking is the storm will impact extreme south Texas, somewhere from Brownsville to Corpus Christi, which is not such good news for these folks.

It's just something we'll have to watch.

In response to my blog question Monday, here is one reply from Missouri.

"Here in Mid-Missouri, there are big, thick, black wooly worms. Lots of folks think that means a hard winter ahead. We had almost 30" at this station last year, so it would be something to beat that! "

Could the black, wooly worms be a tell-tale sign from nature of the potential winter months ahead?

Any more things you all are seeing out there?

Sorry for the short blogs this week. My boss is in town and we are doing a lot of traveling.

What Are Your Cold Season Predictions?

Good morning from a chilly Denver -- it is hovering just about 40 degrees.

There was even a few reports of snowflakes in the southern burbs this morning.

So what are your predictions for the upcoming fall and winter season? I saw one report not too long ago that the Farmers Almanac, which claims an 80-85% forecasting success rate, saying that all but the extreme west and southeast coasts are in for a cold season.

The almanac predicts above-normal snowfall for the Great Lakes and Midwest, especially during January and February, and above-normal precipitation for the Southwest in December and for the Southeast in January and February.

The Northeast and Mid-Atlantic regions should be unusually wet or snowy in February according to the almanac.

The Climate Prediction Center is showing warmer than normal temperatures as we head into the fall season.

So what are your thoughts? Are you seeing any natural signs of a hard winter where you live?

(i.e. the animals are storing up earlier than normal)

I know as a kid in Arkansas, I was always told that thick foliage in the warm season was a sign that a long, cold winter lie ahead.

I don't know that there is any truth to that but that is what some believe.

I heard a reference the other day comparing this year's hurricane season to that of 1995.

So I looked up the winter of 1995-1996 and found this article.

If indeed there is a comparison between the two hurricane seasons, will there be one between the winters too?

According to this one example, then maybe the Farmers Almanac will be right?!?

Of course the bottom line is all we can do is wait and see -- but I do think it is fun to not only look at climatology (past weather) but also any signs our environment might be showing us, if any at all.

Hanna Bringing Beneficial Rainfall

Hanna has moved on shore in the Carolinas, and the CoCoRaHS maps should be quite colorful today from this region.

It will be neat to follow the progress of the rain shield up the coast this weekend as Hanna moves northeast.

Now our eyes will turn to Ike -- a dangerous hurricane. South Florida is really gonna have a close call with this one, and even potentially a direct hit.

If it doesn't hit the mainland of Florida, it may move over the Keys and then get into the Gulf of Mexico - and could potentially threaten Louisiana and Mississippi yet again.

I was checking out websites and found a great video on WRAL in Raleigh, NC that shows storm surge from a landfalling tropical system.

Click here to watch.

Gustav Soaks Chicago-land

Look at the maps for Thursday -- esp. Illinois and Michigan.

Heavy rain soaked much of this region as the remains of Gustav passed through. It dropped a widespread 3 to 5 inches and in some cases more.

Now eyes turn to our east coast CoCoRaHS states as Hanna moves by this weekend.

Then there is Ike -- a major hurricane that is closing in on giving south Florida either a close call or a direct hit.

If you live in this area, have family and friends there, or are planning travel early next week, keep on top of the latest this weekend.

Right now, if the projected path comes true, it will pass just off the tip of south Florida, impacting the Keys, Miami-Dade County, and surrounding areas.

Tropical Trio Threatens Coast

Wow, Hanna is still with us after spinning over a week between the Bahamas and Hispanola.

Now she is on the move and will impact the weather along the coast of the Carolinas this weekend.

Although a threat, I think the real danger is coming on her heels with Ike. Currently a category 4 storm, Ike will be near the Bahamas in a few days.

The remains of Gustav will drop moderate rains today from the Gulf Coast to Michigan. The CoCoRaHS maps remain busy tracking the footprint of this storm system.

Today's Lesson

So yesterday we teased today's topic -- convection!

This is the transfer of heat by the mass movement of a fluid (such as air and water). This type of heat transfer takes place within gases and liquids because they can move freely and currents can set up within them.

In the atmosphere, convection happens naturally.

Once the sun rises each day, the process begins as some areas of the earth's surface absorb more heat from the sun than others.

As a result, the surface is heating unevenly and you get currents or pockets of rising air. Some of the pockets or currents rise higher than others.

This is called differential surface heating and it is one reason why your airplane flight can be bumpy.

Ever flown into Vegas or Phoenix during the summer with clear skies but horrible turbulance? Differential surface heating and thermals in the desert are part of the reason for such a rough ride.

The heated air becomes less dense and expands, rising up. Heat is transferred up in this process.

This air expands and spreads out, eventually cooling and then it slowly begins to sink.

The now cooler, heavier air flows toward the surface to replace the rising air. Eventually the cooler air heats and the process starts all over.

This vertical or upward exchange of heat is called convection, and the rising bubbles of warm air are called thermals.

The cycle of rising air, being replaced by the cooled sinking air, only to heat up and rise again is called a thermal cell.

Taste of Fall

A pool of chilly air has been on the move in the west.

The Front Range awoke to morning temps between 40-45 degrees, with Denver at 46 degrees.

It was cooler north of town toward Ft. Collins and Cheyenne.

Some impressive rain totals keep streaming in from the remains of Gustav.

Some storm totals in Louisiana have reached the 10-15 inch range.

Notice the big hole on our map -- Arkansas. They have seen a widespread 3 to 7 inches and it continues to rain.

Hopefully they will be part of our network next year.

All eyes remain on the tropics. Hannah wants to get her act together and become a hurricane once again. Current models take it very near the northeast coast of Florida, turn slightly northeast and then make a landfall near Myrtle Beach, SC.

That is still days away so we will just have to watch it and see what happens.

Currently, the storm is moving north at 2 mph.

Today's Lesson

Conduction is the transfer of heat from molecule to molecule. An example of this would be to hold one end of a straight pin between your fingers and an open flame and you will soon feel the heat of that flame!

Heat flows from warmer to colder regions.

Some materials, such as the metal pin, are good conductors of heat.

Other materials, such as air, are bad conductors of heat.

Air is such a bad conductor of heat that on a clear, calm day -- heat stored in the ground only warms a shallow layer of air immediately above the ground.

Yet the air can carry energy rapidly from one region to another with no problem. So how if it isn't a good conductor?

The answer is convection.

Tune in to tomorrow's blog for more.

1-2-3-4 Punch?

Well, Gustav is now inland and still doing some damage from flooding rains and tornadoes.

I want to show you an example of how your CoCoRaHS data is being used. (this is just one of dozens of potential examples)

The Hydrometeorological Predction Center, which takes over forecasting tropical systems once they are inland and convert to a remnant low pressure, puts out public statements a few times each day. They always include rainfall totals.

Click here to see the most recent statement. Scroll down and look at the rainfall totals. Notice how many are from CoCoRaHS!

Are any of these totals your total? I'd be pretty excited if they were using my data.

Back to the 1-2-3 and maybe even 4-punch.

There are 3 systems potentially to go.

The most imminent is Hannah, formerly a tropical storm, then hurricane, now back to tropical storm.

It should reclaim hurricane status over the next day or so as it begins to move along the eastern coast of Florida.

Locations from Miami to Virginia Beach should keep an eye on this storm.

Behind Hannah comes Ike and Josephine -- both way out in the Atlantic, but both poised to move into the Caribbean and eventually may threaten the US.

If you like following the tropics and have never been to the National Hurricane Center's website, I encourage you to click here and visit now.

We'll get back into the daily weather lesson hopefully tomorrow. I am short on time today.

Tribute To Odie And A Little Tropics Talk

Odie's Obit

Friday was Odie's viewing and Saturday was her funeral. Wow it was really tough to process that she has departed this world.

I have known Odie since about 2002 when I joined CoCoRaHS and started doing student work with the Colorado Climate Center.

One thing I loved about her was she was very passionate about students. In my educational career, I met all kinds of people. Some that you had to earn your way into their life, and others that met you once and immediately connected -- there to help you with whatever it was you needed, with a very positive attitude.

Odie definitely fell into the immediate connection category.

Later after I graduated with my degree and worked at Channel 7 as the weather producer, I cannot tell you how many times she helped me find weather data for something I was working on.

I was fortunate that I got to visit her two times since the middle of July. Each trip to the climate center we got to visit for about 30 minutes.

On my last trip, near the beginning of August, I told Odie she looked like she was losing weight. In her sweet but slightly sarcastic way, she chuckled and said what are your eyes not working?

I laughed back and said no you are losing weight, I can really see it in your face.

Little did I and anybody know, that was probably outward signs of the cancer her body was fighting.

Odie had been tired and having pain in her legs from what people at the funeral told me. She went for tests to see what was wrong on Aug. 21 and was diagnosed with stage 3 ovarian cancer that was spreading to other parts of her body on Aug. 22.

And just after midnight on the 25th, she passed away suddenly and very unexpectedly.

One of her dear friends spoke at the funeral. She said as hard as it is to think she is gone, the reality she would have faced over the weeks to come with extensive surgery and chemo, the outcome likely would have been the same.

Although no one wants her gone, at least she didn't suffer this way.

I think that was very brave of Odie's friend to say -- and I completely agree.

Please say extra prayers and send warm thoughts to all her friends, family and her husband, Jim.

Also keep your thoughts going Nolan's way too. Next week will be hard for him, returning to the office where he and Odie worked side by side for 30 years.

I am not sure if he is ready for a ton of emails and phone calls. Besides the emotional aspect of returning to work on Tuesday, it will also be back to business with dozens of phone calls and probably hundreds of emails to return.

If you want to reach out, you might consider a thinking of you card. Here is the address to the climate center.

Nolan Doesken
Colorado Climate Center
Department of Atmospheric Science
1371 General Delivery
Colorado State University
Fort Collins, Colorado 80523-1371

Nolan and the climate center are surrounded by a lot of people willing to pitch in and do anything it takes to get through this tough time.

Tropics Talk

It looks like Hurricane Gustav will make landfall in SE Louisiana on Monday as a strong, major hurricane.

Tropical Storm Hannah, currently being impacted by Gustav, is expected to gain strength and parallel the east Florida coast once Gustav moves inland and weakens into a rain producing low pressure.

The SE states (Geogria, N. and S. Carolina) could see impacts from a landfalling Hannah later this week.

There are yet 2 additional disturbances in the far east Atlantic, and they could become the "I" and "J" storms sometime this week.

The hurricane season in the Atlantic Basin peaks around Sept. 10 so this level of activity isn't really all that unusual for this time of year.