Thursday, July 31, 2008

Dogs Days of Summer

The "dog days of summer" are upon us. This refers to the hottest, most sultry days of the year, typically starting in mid to late July and lasting through most of August.

The period is best described as hot and stagnant with little progress or change in the weather patterns.

The term "dog days" was used by the Greeks and Romans as they tracked Sirius (the Dog Star). It was popularly believed to be an evil time when the seas boiled, wine turned sour, dogs grew mad and man became sick with fever and hysterics.

The "dog days" originally were the days when Sirius rose just before or at the same time as the sun.

For ancient Egyptians, the star Sirius appeared just before the season when the Nile River flooded. The this also was the time the weather turned hot and sultry. It prompted the saying, "Dog Days bright and clear, indicate a happy year. But when accompanied by rain, for better times our hopes are vain."

"Dog Days" are also associated with the US Stock market, since in the summer stocks tend to be slow and poorly performing stocks with little future potential are called dogs.

And in hot, humid climates, the dog days are associated with "dogging" around, or being "dog tired."

Today's Lesson

If you were to go out and start a meteorology degree, chances are you will have to get a minor in math, or at least take several classes in the field.

Meteorology coursework involves a lot of work with equations.

We'll do a little basic math in today's topic.

Although the atmoshere extends several miles above the Earth, most of it can be found closest to the surface.

This is because of gravity, pulling down on the air above, and squeezing (or compressing) air molecules closer together.

The more air above a certain level, the greater the squeezing force.

Gravity also has an effect on the weight of objects, including air. In fact, weight is the force upon an object due to gravity.

Mathematically, weight = mass X gravity.

Here is an example. Say you have a container of air, it'd weigh the same anywhere you travel on Earth. But if you instantly went to the moon, where the force of gravity is 1/6 of what it is here on Earth, that same container of air would weigh 1/6 less on the moon.

Now let's talk about two different measurements, mass and volume.

Mass is the weight of an object, and is measured in grams or kilograms typically.

A volume is telling you how much matter is in a given space. Since it is a space, volume is expressed in cubic measurements. (usually cubic centimeters or meters)

I know that is a lot to take in -- esp. if you are one that tends to get lost with any type of math talk.

I had to introduce that before we dive into density and pressure, two things you really have to grasp to understand weather.

We'll get into that tomorrow.

Wednesday, July 30, 2008

Hot For Most, Wet In The Middle

Well it seems like a broken record, more rain for the middle of the country -- with Missouri being the bullseye.

This time is seems to be heavier on the west side (Kansas City) as opposed to the east side (St. Louis) but that could change as the day wears on.

I was reading about several flooding reports in and around Kansas City due to 2-4 inches of rain overnight.

Go to the maps section of CoCoRaHS and click on Missouri, then pull up just Jackson County.

That is really something to have that many widespread reports right at 4 inches. Usually you see a good size thunderstorm with a small target of one report at 4 inches, and all the surrounding reports might be more in the 1-3 inch range.

That thunderstorm had a large and VERY WET center, and put down BILLIONS of gallons of water on that county.

It remains hot all over, including here in Denver. Today will be Day 18 with temps in the 90s -- which ties the longest streak of 90-degree days ever for the city.

We are expected to be in the upper 90s and even lower 100s well into next week. Pretty remarkable!


There are a few more aspects of the atmosphere we need to explore. Ozone -- not the pollution found at the Earth's surface, but the atmospheric kind, found way up high in the stratosphere.

It forms naturally as oxygen chemicals combine with oxygen molecules.

The ozone layer shields life on Earth from the sun's harmful ultraviolet rays.

There are also impurities from both human and natural sources that become airborne within the atmosphere.

They are called aerosols -- and include smoke from forest fires, ash from volcanoes, dust from dry fields, and small saltwater droplets from the oceans.

Some natural impurities are beneficial to us because they act as surfaces on which water vapor condenses to form clouds. (almost like cloud seeding)

But there are also bad, human-made impurities called pollutants in the atmosphere, such as exhaust from automobile engines.

Now that you have an introduction to the atmosphere and it's composition, it is time to look at the vertical structure.

If you took a slice of the atmosphere, meaning from the ground up as far as the eye can see, and looked at the profile of it -- you would notice that it could be broken up into a series of layers.

Each layer could be defined in a number of ways, including how the temperature varies through it, the gas composition and it's electrical properties.

For weather, however, there are really two main things you need to worry about when looking at the atmosphere in the vertical (from the ground up) and that is air pressure and air density.

Tomorrow we will explore this more...

Are you enjoying these lessons? I know it is a little dry and you probably want to dive right into thuderstorms, hurricanes, tornadoes, etc.

But you have to have at least a basic understanding of the atmosphere before the rest will make sense.

We'll get there soon enough, I promise!

Tuesday, July 29, 2008

Rains Soak Much Of Kansas

Much of western and central Kansas saw a good rainfall on Monday, which was really welcome. It was all thanks to the remnants of Hurricane Dolly.

Some locations in eastern Colorado and western Kansas have been extremely dry.

Another area that saw liquid gold from Mother Nature was the Smoky Mountains of western N. Carolina and eastern Tennessee.

Click here and you will be able to see that both of these areas really needed the moisture, as shown by the US Drought Monitor.

What they didn't need was the damage that came along with the rain in parts of North Carolina. Observer NC-CK-1 left a note in today's comments that they had to assist the fire department in clearing downed trees from the thunderstorm.

Today's Lesson: Carbon Dioxide

Carbon Dioxide is a natural component in the atmosphere, and occupies a small but important percent of the air.

It comes from the decay of vegetation, volcanic eruptions, the exhalations of animal life, deforestation and the burning of fossil fuels.

It is removed from the atmosphere by photosynthesis of plants, and is stored in roots, branches and leaves.

The ocean is also a huge reservoir of carbon dioxide, as phytoplankton (tiny drifting plants) trap the gas. Carbon dioxide also can mix down into the water and circulate with the ocean currents.

The problem with carbon dioxide is that it is a greenhouse gas, just like water vapor, which we talked about in yesterday's blog lesson.

It traps a portion of the Earth's outgoing energy.

Consequently, with everything else being equal, if carbon dioxide increases, then so should the average global temperature.

Scientists have proven that since the industrial revolution, the levels of carbon dioxide on our planet have continued to rise.

There are a few other greenhouse gases that have been getting attention over the past few years....methane, nitrous oxide and chlorofluorocarbons.

Tomorrow we will learn a little more about the atmosphere before we take a look at the vertical structure -- which should help you start understanding a little more about the weather around you.

Monday, July 28, 2008

Earth's Atmosphere -- Water Vapor

More heavy rains fell across New Mexico on Sunday, all thanks to the remnants of Dolly.

Can you believe that some places have seen nearly an entire year's worth of precipitation in just one weekend?

A large complex of strong to severe thunderstorms developed over central Iowa and pushed southeast, almost following the Mississippi River perfectly late Sunday. In fact some locations saw two rounds of storms.

These people just can't seem to catch a break from all the heavy rain and flooding.

Between 4pm Sunday and 1am Monday, the Ankeny Airport in Polk County, Iowa saw 4.88 inches of rain.

Several places also saw large hail, up to 3 inches in diameter in parts of the region.

The town of Pollock, Missouri (Sullivan County) saw up to 5 minutes of very large hail that measured 4.50" in diameter at times. There was a tremendous amount of damage to cars and windows as you can imagine.

Most of the St. Louis metro area picked up 1-3 inches of rain from the storms.

The CoCoRaHS maps will be exciting today to say the least so be sure to explore the maps and the daily comment reports.

Over 2 dozen intense rain reports were filed on Sunday -- great job volunteers!!!

On to our first weather lesson...the Earth's atmosphere.

The Earth's atmosphere is a complex, thin, gaseous envelope made up mostly of nitrogen and oxygen.

There is another gas found on Earth called water vapor. It varies greatly from place to place.

In warm, tropical places it can account for up to 4% of the atmospheric gases, but in cold, arctic areas it can be a mere fraction of the atmospheric composition.

Water vapor is invisible until it becomes either a liquid or solid, such as cloud droplets or ice crystals.

The changing of water vapor into liquid water is called condensation (think of dew) and the opposite is called evaporation.

Water vapor is EXTREMELY important to our atmosphere and the weather we experience. Not only does it form into liquid and solid cloud particles that grow in size and provide precipitation to the Earth, BUT it also releases large amounts of heat -- called latent heat -- when it changes from vapor into liquid water or ice.

Latent heat is an important source of energy for storms.

Water vapor is also a potent greenhouse gas because it abosrbs a portion of the Earth's outgoing radiant energy. (kind of like the glass in a greenhouse keeps the heat from escaping and mixing with the outsdie air)

So as you can see, water vapor plays a significant role in the Earth's heat-energy balance.

Sunday, July 27, 2008

Hello Dolly!!!

The remains of Dolly really brought some liquid gold to much of New Mexico on Saturday, with one observer in the town of Sunspot racking up over 6" of rain.

The comments were really fun to read. One person said it was the most rain since 1981! Many had their inner tube overflow. (which I can say from personal experience is VERY exciting!!)

In yesterday's blog I asked for your feedback. All I can say is WOW!

Thanks for the phenominal comments -- they really meant a lot to me.

For the most part you all like what I have been doing, but some have asked for me to teach basic weather principals.

Others asked for precipitation outlooks. Someone even asked about old weather folklore.

Well here is what I have decided to do.

I dug out all my old textbooks and classwork from when I was in college, and have decided to give myself a refresher and hopefully teach you a thing or two also.

So we'll start right at the beginning with Introduction to Meteorology.

If anyone is curious as to what I am looking at, I am using my textbook called Meteorology Today, An Introduction to Weather, Climate, and the Environment -- Sixth Edition.

Here is a link to that on Amazon if anyone is so into weather that they would like a copy.

Click here.

It will bring up the 7th edition, but I am sure if you look in the used books you can get an earlier version cheaply if you want to.

So starting tomorrow I will just pick through Chapter 1 and highlight things that you might find of an interest.

Also, for those interested in long range outlooks -- here is a great website for you to bookmark.

The Climate Prediction Center. Click here.

There you will find some great info on both short and long-term outlooks, and well as weather hazards expected over the next few days.

So get ready for class tomorrow -- it will start at 8 am SHARP!! Only kidding, you all should know by now that I am NOT an early riser. ;-)

Saturday, July 26, 2008

Readers Survey

Happy Saturday everyone!

I just want to take a quick poll of the blog readers.

If you could just tell me where you live and what you like about the blog or what you would like me to write about that would be great.


Friday, July 25, 2008

Foot Of Rain Falls In Show Me State

CoCoRaHS observer MO-FSA-001 said it was the biggest rain they have ever witnessed -- with over 12" falling in 31 hours.

The gauge actually overflowed and they aren't sure how much data was lost.

This report comes from Adair County, near the town of Kirksville.

2-3 feet of water covering approximately 30 roads in and around Kirksville has prompted over a dozen water rescues.

Up to 4 feet of water has surrounded homes and covered highways in Ralls County near the town of Perry, where several large unoccupied campers were washed away by Lick Creek.

There are several flash flood warnings in effect today for central and northern Missouri.

The area hard hit by heavy rain is basically the same locations hit by floods earlier in the summer. (north and northwest of St. Louis)

Thursday, July 24, 2008

Mesoscale, Synoptic Features & Dolly

Well it is not surprising to see the highest rainfall totals on today's national map coming from south Texas.

Hurricane Dolly dropped a swath of 6-12 inch rainfall totals from near Brownsville to San Miguel.

We finally saw rain here in the Denver area on Wednesday, and should see more later in the weekend as the remnants of Dolly are forecasted to move through as it gets caught up in the monsoonal flow from the southwest.

Elsewhere there was some very heavy rains in New York yesterday, with flash flooding reported in several communities.

There was even a family trapped in their home by rising flood waters in Sullivan County.

Golf ball sized hail fell on Wednesday in Rapid City, South Dakota from a left-turning supercell thunderstorm.

Penny-sized hail fell at the airport in Philly, and there was some wind damage associated with thunderstorms in Florida.

This time of year the weather is very random -- there are all kinds of "small-scale", or as we call it in meteorology, "mesoscale" features going on.

Yesterday we were tracking a hurricane, a few small cold fronts, daytime heating interacting with low-level moisture in place, a low pressure, etc.

In the spring and winter months we are usually tracking one big "large-scale" or "synoptic" feature like a cold front that sweeps across the entire US.

Wednesday, July 23, 2008

Dolly Moving In, Some Heating Up

A bubble of high pressure and hot air will strengthen over the south-central plains the rest of this week.

A broad area of 100-105 degree heat will be found from southeast Colorado and southwest Kansas, down into northern Texas. (roughly from Lamar, Colorado to Dodge City, Kansas -- and extending down through Oklahoma City into the Dallas area)

Meanwhile, residents of extreme south Texas and northeast Mexico will deal with heavy rain, wind and a few tornadoes as Dolly roars ashore today.

We have already had 1 intense rain report today from Cameron County, Texas. I am sure there will be more if the observers can safely file a report, or if they have power!

Tuesday, July 22, 2008

Heat Index

Well it's July and you'd expect nothing less from Mother Nature this time of the year -- but I have to say that I am SO glad to be in Colorado where there humidity is low and not in Mississippi where it is high!

I was just checking a few observations in the southern states and there are places already at 85 to 90 degrees with a heat index above 100! It is still morning!

The heat index is just a "feels like" temperature -- meaning what your body feels due to the amount of moisture in the air.

Here in the west, we actually have a negative heat index at times during the summer because it is so dry.

The sweat evaporates off your body so fast it actually has a cooling effect.

The other day here in Denver it was 98 degrees with only 8% humidity. I think the heat index was something like 95 degrees.

Monday, July 21, 2008

C'Mon Dolly -- Bring Us Some Relief

Tropical Storm Dolly (although I am sure sometime today it will become a Hurricane) is over the Yucatan and ready to move into the warm Gulf of Mexico.

The current projected 5-day path has it making landfall as a strong hurricane not too far away from Brownsville, Texas.

The storm is then anticipated to move inland across northern Mexico and dissipate.

So where will that HUGE plume of moisture go -- I am hoping it can sneak in under the high pressure over the west and join up with the monsoonal flow into the Rockies.

Arizona, New Mexcio and southern Utah and Colorado have been getting some very beneficial rainfall.

But in the Denver area, we can't buy a drop of rain, much less a good thunderstorm.

Yesterday we had a fire breakout not too far from the southwest suburbs of Denver, very near where the largest forest fire in Colorado history burned in 2002.

It was quickly fought, and although still burning, hasn't grown much more than the 140 acres burned so far as of writing this blog.

As usual it seems (as far as this summer goes) the Monday CoCoRaHS map is lit up like a Christmas tree across the midwest, from Iowa to Indiana.

The observer near Clive, Iowa has recorded over 4.50 inches of rain since Friday.

Some good rains also fell in the northeast states on Sunday, with nearly 2 inches of rain in south-central Upstate New York.

Sunday, July 20, 2008

Cristobal Grazing By Carolinas

Tropical Storm Cristobal is just barely skirting by the outerbanks of North Carolina today, but other than the angry sea, you would hardly know that a tropical storm is just 50 miles off shore.

The circulation of winds around Cristobal is sucking in a lot of dry air, so with the exception of the extreme outerbanks, most locations are reporting sunny to just partly cloudy skies.

There could be a few squally, gusty thunderstorms that put down a lot of rain in a short period of time, but on the whole, Cristobal is really no big deal for local residents.

Friday, July 18, 2008

Heavy Rain Event Captured By CoCoRaHS

I am not sure how many of you saw a national radar map on Thursday evening, but a huge complex of showers and thunderstorms made its way through southeast Nebraska and portions of Kansas and Iowa.

I sat there and thought to myself, wow -- I wonder how well CoCoRaHS will record this "storm footprint"?

All you have to do is look at today's national map and you can see it like a clearly marked target.

There was definitely a bullseye in southern Jefferson and Thayer counties (in south-central Nebraska) with some 4 and 5 inch reports.

But there were numerous 3-inch+ reports in Kansas, Iowa and Nebraska.

Thursday, July 17, 2008

More Big Rains In Florida

Florida has seen another day of widespread heavy rain, and it is thanks to a tropical low sitting over the state.

If this low was just a matter of miles east or west of the peninsula, it would have potentially developed into something tropical.

However, since most of the circulation has been over land, it has remained weak and not been able to take on tropical characteristcs.

BUT what it has been able to do is create enough lift in the atmosphere to drop locally heavy rains --- mainly over the central peninsula from Tampa to Orlando and surrounding areas for the past few days.

Elsewhere it is more of the same. The west is dry and hot with the exception of the monsoon moisture. The upper midwest is wet and stormy, as has been the case much of the season.

The observer 3.4 NNW of Hoover, AL received 0.40 inches of rainfall on Wednesday and left "GOT LUCKY" in the comments.

I know several of us have all felt that way at some point this year!

Wednesday, July 16, 2008

Western Fires

I had a nice comment yesterday from an observer asking me about western fires.

The first question is what do they mean when they say a fire is so many percent contained?

This is referring to a defense line being built around the actual perimeter of the fire. This is usually either built by hand or dozer.

So if a fire is 65% contained, they are saying they have built a line around 65% of the fire and that it should not spread beyond that boundary.

It does not mean that the stated percent of the fire is out.

Sometimes a containment line is built and then winds pick up and the fire jumps the defense line.

As you can imagine this is VERY frustrating for firefighters, but part of the reality.

The second part of the question was where does all the fresh water come from to fight fires, given that water isn't as plentiful in the west as in other parts of the nation.

The water comes from area lakes and reservoirs typically. I imagine there are politics involved and which lakes provide the water likely depends on each individual fire.

If towns are immediately threatened, I would think that higher priority lakes (public reservoirs for example) are allowed to be used as a source.

If the fire is serious but not threatening an immediate large population, they probably use lakes that aren't a major water supply source.

That is just my opinion, but I do know in general much of the water you see dropped from air tankers and helicopters is scooped up come from lakes.

Tuesday, July 15, 2008

Soaking Rains In Louisiana, Florida

As of 9 am MT Tuesday, the top CoCoRaHS report for Monday went to the observer 0.9 NNW of Labadieville, Louisiana -- with a whopping 4.33 inches of rain from a thunderstorm.

The observer described the lightning as intense and close along with some flooding.

There were also some heavy rain reports in Florida with a few locations pulling in over 3 inches of rainfall.

We sure could use that here in the Mile High City!! So far this year we are nearly 6 inches behind normal, making it the 4th driest year on record to date.

11 observers filed intense rain reports on Monday, from Georgia, Florida, Virginia, Texas, Louisiana and Maryland.

Monday, July 14, 2008

Quiet For Most, Wet For Some

It's a fairly quiet start to the weather week for most with the exception of the southern and eastern fringes of the USA.

Starting in the deserts of Arizona and New Mexico, the monsoon is really dumping a lot of rain on some.

There's been all kinds of flash flooding over the past week.

You can many great reports and comments from the CoCoRaHS spotter network in New Mexico.

The flow of monsoonal moisture will push north this week into the central part of the Rocky Mountains, great news for Colorado, portions of Utah and Wyoming.

Along the Gulf Coast states, an old front has been kicking up showers and thunderstorms with some MUCH NEEDED rainfall.

This past weekend dumped 1-2 inches of rain on places like Atlanta, GA and Birmingham, AL.

The CoCoRaHS observer near Valley, AL recorded 3.51 inches of rainfall on Sunday from a good ole GULLY WASHER!

A cold front pushing off the east coast of the US will keep unsettled weather along most of I-95 today.

Sunday, July 13, 2008

Tropics Heating Up

The National Hurricane Center is still tracking Bertha, now a Tropical Storm.

Check out the forecasted track over the next 5 days.

The storm really has nothing significant to steer it one way or the other so Bertha is just kinda meandering around, being influenced by the sub-tropical high pressure over the Atlantic, the westerlies aloft and an approaching cold front off the east coast.

Hopefully Bertha won't linger too long out there -- because if it does and conditions change, she could eventually be a problem for someone.

Meanwhile, two new areas of disturbed weather are being watched, including one right off the coast of the Carolinas.

An old frontal system is parked off the coast and is stirring up some showers and thunderstorms along with an area of lower pressure.

A third area of unsettled weather is being tracked about 1600 miles east of the islands -- not too far from where Bertha originated. The only difference is this new aera is a bit further south and west, which means if it develops, it would have a better chance of impacting the islands and maybe even areas closer to the US mainland in time.

It should definitely be watched over the next week!

Thursday, July 10, 2008

Bertha Turns North, Heads For Cooler Water

The second named storm of the 2008 Atlantic Hurricane Season is making a turn toward the north today and will move east of Bermuda over the next 48 hours.

The storm will continue to weaken over the next 5 days as it heads into the colder water of the northern Atlantic Ocean and gets caught up in the jet stream.

If you are traveling to the western coast of Mexico this weekend -- there are a few areas of disturbed weather along the SW coastline that could hamper some plans.

So keep an eye on the National Hurricane Center's website for the latest information.

Wednesday, July 9, 2008

Record Heat Continues Across California

It's hard to imagine what day after day of 100°+ temperatures must feel like for most of us CoCoRaHSians.

A really strong, persistent ridge of high pressure continues to dominate much of the west.

Highs have been reaching into the 100s for locations in the LA Basin all the up to north and east of San Francisco.

The heat is expected to last into the weekend, with only a slight cool down for some.

If you want to escape the hot weather, head to the UP of Michigan -- where the Queen City of Marquette is forecasting highs in the upper 60s and lower 70s over the next few days.

Tuesday, July 8, 2008

Monsoon Season Is Here

A huge part of the summer weather pattern here in the west is the annual monsoon.

The North American Monsoon, sometimes called the Mexican Monsoon, usually begins during the first week of July and lasts into the month of September. It can start as early as late June.

What exactly is a monsoon?

It is a seasonal shift in the wind pattern that usually lasts for a few months -- and in our case or the case of places like India -- that shift brings the wind pattern off a major body of water, and thus it transports moisture into the region.

For states like Colorado, Arizona, New Mexico and Utah -- it is a VERY critical part of the local climate, and provides very beneficial moisture to this arid part of the world.

Up until this year, the monsoon was declared active when the dewpoint temperature in Tucson, Arizona reached 54 degrees or higher for 3 consecutive days. The start date could range anywhere from June 25 to July 10.

Now, the National Weather Service is simply defining a monsoon season, which runs from July 1 through September 30. It is just easier when teaching public awareness to define an exact date range rather than waiting each year to see when it officially starts and ends.

Monsoon season brings a huge threat of flash floods.

If you like to watch the US satellite and radar, keep an eye on the 4 corners. Almost like clockwork, over the next several weeks, our states like up like a Christmas tree with radar returns shortly after the noon hour.

The daytime heating interacts with the moisture coming off the Pacific Ocean -- and we get numerous showers and thunderstorms.

Usually they have gusty winds, small hail and brief but very heavy rain. Tornadoes aren't usually a threat this time of year, but sometimes they can spin up for a few minutes.

Monday, July 7, 2008

Pert Near Washed Away!

Ok many of your know I am from the south originally -- and between Minnesota and Colorado I have managed to lose SOME of my "twang."

My family thinks I sound like a northerner -- but others still know where I am from.

Anyways -- the "pert near" is kind of a popular phrase where I come from in Arkansas.

Over the 4th of July weekend I decided ok, starting Monday, you have to get back to blogging -- so I made a vow to do so today (Monday).

And boy do I have a story to tell.

If you go to maps and look at the Denver Metro map, you will see my dot. Unless another area observer (and there aren't many as my part of town in new and still developing) filed a report after me, someone looking at the data would think there was a mistake.

All area reports are about a quarter inch or so and there is my 1.50+ inch rainfall!

I wasn't home, I was on the westside of town but could see the dark, nearly black cloud to the east. I knew it was near my place, but one can never tell -- the sky exposure is so huge in this part of the world what looks like right over your house may actually be 40 miles further east!

Well, I came home to see my flowerbeds washed away -- all the mulch and some dirt washed up against the fence. Mud was splattered and caked all along the bottom of the fence posts.

I estimate based off the incredible erosion that the rain fell over an hour or so, and really intense for about 20 to 40 minutes.

See the pictures below. Check out the dirt formerly in my yard that is now on the greenbelt path behind my home!