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.