Ramblings of a Graduate Student

Friday night I discussed the possibility of setting up another southern snow storm.  All current indications are the are suggesting another Texas snow storm late Monday night into early Wednesday.  This will be the second snow storm for portions of central and northern Texas in less than two weeks.  (Remember, 11-12 February portions of northern Texas – including the Dallas-Fort Worth metropolitan area – received over a foot of snow.)

The image above is from the National Weather Service’s Hydrometeorological Prediction Center.  It is the probability of a given point receiving over 8″ of snow between 00Z Tuesday (6 PM CST Monday) and 00Z Wednesday (6 PM CST Tuesday).  Notice how areas south of the Dallas-Fort Worth metropolitan area have a 10% chance of receiving 8″ or more of snow – including the Waco, TX area.  Per the NWS office in Fort Worth, the last time Waco, TX received 4″ of snow was 1982.  This has been one of the greatest winters ever!

As many of you may already know, I’m currently attempting to take “a snow shot of America” tomorrow.  For those who don’t know what that is, you may be wondering what on earth is “a snow shot of America”.  Simply put, it is a collage of pictures taken of the snow on the ground from every state.  Why tomorrow?  There is a chance that there will be snow on the ground in all 50 states at the same time.  It is unclear if this has ever happened in recorded history.

Above is this morning’s National Snow Analysis; it excludes Alaska and Hawaii, but I’ll get to those states in a minute.  As you can see by looking at the analysis, snow exists in same form or fashion in every one of the contiguous states, with the exception of Louisiana and Florida.  However, a storm moving across the southern United States is poised to change that map drastically by tomorrow.  Local National Weather Service offices in the Deep South are currently forecasting up to an 1″ of snow as far south as the beaches of far western Florida Panhandle.  2-4″ may be possible in areas just north of Pensacola, FL.

Below is the current National Watch/Warning graphic.  The hot pink color is Winter Storm Warnings.  It isn’t very often you see these extended all the way to the Gulf Coast.  Nor do you see it over such a large area this far south.  Here’s to hoping for Florida snow tomorrow!

Now, about Alaska and Hawaii…Alaska has a lot of snow in the state, so I’ve never worried about them.  I was led to believe based on a The Weather Channel tweet that there was snow in the mountains of Hawaii.  This seemed perfectly logical to me, so I didn’t question it too much.  Old webcam images showed snow, and a blizzard in the past few weeks blanketed the mountains.  However, further investigation has led doubt to finding snow on the mountains.  It certainly seems possible that there is snow in a sheltered patch, however, finding the snow will be tough.  I keep reminding myself that “absence of evidence is not necessarily evidence of absence”.  In other words, just because we can’t find it, doesn’t mean it isn’t there.  Here’s to trying!

In any event, Florida snow is more rare than Hawaiian snow, so getting 49/50 and the 48 contiguous states is still an impressive feat!

A very active weather pattern continues across the contiguous United States this evening.  There are no less than five upper-level lows, two jet streams (Polar and Subtropical), two very well defined warm conveyor belts, and much, much more!

Today’s post is a little bit different than previous posts.  Instead of me discussing a map, I’m giving you a chance to test your own skills.  Take a minute to try and identify all of these things on your own and then click below for the answer.  Good luck!

For those who would like some help, here is an animation of the 24 hours leading up to the image above: 10 February 2010 Water Vapor Loop.

Answer Key

Edit: After being contacted and asked if there were more than the 5 upper-lows / vorticity maximums / shortwave troughs that I have annotated, I have uploaded a new answer key marking the two most commonly identified upper-lows / vorticity maximums / shortwave troughs that I did not have marked in my initial answer key.  There could easily be more (such as associated within the warm air advection occurring off the west coast), but I’ve now identified 7 more obvious ones.

Today weatherpersons all across the United States are celebrating National Weatherperson’s Day.  I know a lot of people consider Groundhog Day (2 February) to be National Weatherperson’s Day because, after all, what screams weatherperson more than a furry rodent looking for its shadow?  However, they would be wrong.  It is celebrated on 5 February because today is the anniversary of American John Jeffries’ birth, who began recording daily weather observations in Boston, MA in 1774.  Jeffries is considered to be one of the first weather observers in what became the United States.  This day celebrates meteorologists’ continuous efforts to produce the best forecasts and warnings.

With this said, there is a lot of high-impact weather to observe across the United States today.  The strong shortwave trough over eastern Colorado last night has continued to dive east-southeast into central Kansas and is aiding in the development of widespread snow across eastern Kansas and much of Missouri.  Also, the conglomeration of weak shortwave troughs over the Gulf of Mexico last night continue to track off to the northeast aiding the development of extremely widespread precipitation across much of the eastern United States.

The areas shaded in blue are places where a computer model believes the precipitation is falling as snow; orange is a mixture of rain, freezing rain, sleet, or snow; and green is rain (or thunderstorms).  As you can see, snow is evident from the far western edge of the map (in reality it extends all the way into Missouri) all the way to the east coast.  All of this precipitation will slowly move east over the next 24-36 hours yielding a near historic snowfall for the Washington D.C. area.  In fact, Washington D.C. is under a Blizzard Warning!  16-22″ of snow is expected to fall overnight!

Below is the text of a Special Weather Statement issued by the National Weather Service Forecast Office in Sterling, VA (which covered the Washington D.C. metro).  Notice the strong wording and the 20-30″ totals that are expected.  Earlier today I saw some model guidance that predicted almost 40″ of snow!  Sheesh!

000
WWUS81 KLWX 051734
SPSLWX

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1234 PM EST FRI FEB 5 2010

DCZ001-MDZ004>007-009>011-013-014-016>018-VAZ042-050>057-501-502-
060145-
DISTRICT OF COLUMBIA-FREDERICK MD-CARROLL-NORTHERN BALTIMORE-
HARFORD-MONTGOMERY-HOWARD-SOUTHERN BALTIMORE-PRINCE GEORGES-
ANNE ARUNDEL-CHARLES-ST. MARYS-CALVERT-LOUDOUN-ORANGE-CULPEPER-
PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-
ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA-
KING GEORGE-NORTHERN FAUQUIER-SOUTHERN FAUQUIER-
INCLUDING THE CITIES OF...WASHINGTON...FREDERICK...WESTMINSTER...
GAITHERSBURG...COLUMBIA...BALTIMORE...ANNAPOLIS...WALDORF...
ST MARYS CITY...LEESBURG...CULPEPER...MANASSAS...MANASSAS PARK...
FAIRFAX...ALEXANDRIA...FALLS CHURCH...FREDERICKSBURG...WARRENTON
1234 PM EST FRI FEB 5 2010

...RECORD SNOWFALL FORECAST IN THE BALTIMORE-WASHINGTON DC REGION...

...EXTREMELY DANGEROUS WINTER WEATHER CONDITIONS DEVELOPING TONIGHT...

GUSTY NORTHEAST WINDS 20 TO 30 MPH WITH VISIBILITIES FREQUENTLY
FALLING BELOW ONE-QUARTER MILE DUE TO HEAVY SNOW WILL DEVELOP
TONIGHT TO PRODUCE NEAR-BLIZZARD AND EXTREMELY HAZARDOUS WINTER WEATHER
CONDITIONS TONIGHT THROUGH SATURDAY MORNING.  TRAVEL IS HIGHLY
DISCOURAGED TONIGHT AND WILL BE VERY DANGEROUS.

LOOKING BACK AT THE BIGGEST STORM OF RECORD FOR WASHINGTON DC... THE
JANUARY 1922 KNICKERBOCKER STORM...28.0 INCHES OF SNOW WAS
PRODUCED FROM 3.02 INCHES OF LIQUID WATER.  CURRENT FORECASTS FOR
THIS EVENT HAVE TOTAL LIQUID FALLING FROM THIS STORM APPROACHING 3
INCHES...WHICH ACCORDINGLY WOULD CREATE A SNOWFALL THAT WILL RIVAL
THE KNICKERBOCKER STORM TOTAL.  GENERALLY ACROSS THE REGION...20 TO
30 INCHES OF SNOW WILL FALL BY SATURDAY EVENING.

BALTIMORES RECORD OF 26.8 INCHES FROM THE PRESIDENTS DAY FEBRUARY 2003
STORM WILL ALSO BE THREATENED.

A FEW PRECAUTIONARY AND PREPAREDNESS ITEMS TO NOTE:

1.  FOLLOW MANUFACTURERS INSTRUCTIONS WHEN OPERATING A GENERATOR OR
AXILLARY HEATER.  ENSURE PORTABLE GENERATORS ARE ADEQUATELY VENTILATED.

2.  TRAVEL CONDITIONS TONIGHT ACROSS THE REGION WILL BE EXTREMELY
DANGEROUS AND LIFE THREATENING.  HELP YOUR LOCAL AND STATE
GOVERNMENT FIRST RESPONDERS AND TRANSPORTATION AGENCIES BY STAYING
OFF ROADS LATER THIS EVENING AND TONIGHT.

3.  FOLLOW LOCAL AND STATE GOVERNMENT EMERGENCY DECLARATION ORDERS.
IF YOU ABSOLUTELY NEED TO TRAVEL IN AN EMERGENCY...DO NOT TRAVEL
ALONE.  LET SOMEONE KNOW YOUR TIMETABLE AND YOUR PRIMARY AND
ALTERNATE ROUTES.  CARRY WITH YOU A WINTER STORM SURVIVAL KIT WHICH
INCLUDES A MOBILE PHONE...BLANKETS...FLASHLIGHT WITH EXTRA
BATTERIES...HIGH CALORIE NON-PERISHABLE FOOD AND WATER...AND A
SHOVEL.

4.  IF YOU GET STRANDED IN YOUR VEHICLE...DO NOT LEAVE YOUR CAR TO
TRY TO WALK FOR ASSISTANCE...YOU CAN QUICKLY BECOME DISORIENTED IN
WIND DRIVEN SNOW AND COLD.  THIS STORM WILL SUBSIDE SATURDAY
AFTERNOON...SO WAIT IN YOUR CAR FOR EMERGENCY HELP TO ARRIVE.
PERIODICALLY RUN YOUR ENGINE FOR ABOUT 10 MINUTES EACH HOUR FOR
HEAT. ENSURE YOUR EXHAUST PIPE IS CLEARED OF SNOW AND ICE.  CRACK
YOUR WINDOWS TO AVOID CARBON MONOXIDE POISONING. TIE A COLORED CLOTH
TO YOUR CARS ANTENNA TO BE VISIBLE TO RESCUERS. FROM
TIME-TO-TIME...MOVE YOUR ARMS...LEGS...FINGERS...AND TOES TO KEEP
BLOOD CIRCULATING.

5.  AVOID OVEREXERTION WHEN SHOVELING SNOW.  BREAK THE SHOVELING
DOWN INTO SMALLER JOBS AND TAKE FREQUENT BREAKS.

6.  IN CASE OF POWER SUPPLY DISRUPTIONS...HAVE AVAILABLE FLASH
LIGHTS WITH EXTRA BATTERIES...EXTRA FOOD AND WATER...EXTRA MEDICINES.

7.  ENSURE ANY PETS AND FARM ANIMALS HAVE PLENTY OF WATER...FOOD...
AND SHELTER.

FINALLY...THE KEY TO GETTING THROUGH THIS AND OTHER PERIODS OF
HAZARDOUS WINTER WEATHER IS WITH ADVANCE PLANNING AND BEING AWARE OF
CURRENT CONDITIONS.  THIS STORM WILL BE WINDING DOWN EARLY SATURDAY
EVENING...SO DO YOUR PART AND LET YOUR LOCAL AND STATE GOVERNMENTS
RESTORE ROADWAYS TO NORMAL CONDITIONS BY STAYING AT HOME.

$$

LEE/CS

As I alluded to in last night’s post, the mid-Atlantic states are preparing for what could be their second major snow storm this winter.  Back in mid-December, portions of the mid-Atlantic received upwards of 2 feet of snow from storm very similar to the one forecast to affect the area tomorrow into early Sunday.  Tonight I thought I’d take a few minutes to jot down a few remarks about the ingredients coming together in the mid-troposphere to enable such a major winter storm.  We’ll begin with my favorite piece of observational data – the water vapor satellite image.  I’ve previously mentioned why water vapor imagery is so valuable to meteorologists, so I’ll spare you the repeat of information.  Suffice it to say, if I could only look at one chart a day, this would be the one I would choose.

I’ve identified several shortwave troughs (upper-low) / vorticity* maximums in the above water vapor image via a yellow ‘X’.  [As an aside, meteorologists are often interested in minimums (min) and maximums (max) in vorticity.  To label these phenomena, meteorologists use a 'N' for the miNs and a 'X' for the maXs.]  Looking at the above image, I’ve used two big ‘X’s and two small ‘x’s.  The size of the ‘X’ is to help identify the stronger maximums in vorticity (shortwave troughs / upper-lows).  We’ll ignore the strong shortwave trough off the west coast as it will have little, if any impact on the east coast snow storm.

There is a minor shortwave trough over central Texas that is heading northeast toward eastern Oklahoma.  This shortwave trough will most likely be absorbed into the larger trough that is moving east-southeast out of eastern Colorado.  There is also a minor shortwave trough over the central Gulf of Mexico that is lifting northeast toward Georgia.  It is this shortwave trough that will begin to affect the east coast late tonight into Friday with the first bout of precipitation.  I’ve also circled an area of the western Gulf of Mexico in yellow.  I believe that there is another minor shortwave trough somewhere in the circled area, but it is not discernible from a single satellite image.

Over the next 48 hours, the shortwave tough(s) over the Gulf of Mexico will move toward Georgia and then off the mid-Atlantic coast. This trough will help to draw warm, moist air northward from the Gulf of Mexico into the mid-Atlantic region.  This warm, moist air will encounter very cold air at the surface causing the warm, moist air to be lifted into the atmosphere.  Widespread precipitation – in the form of snow in areas away from the coast – will begin to develop and spread northward overnight into tomorrow as a result of this.  At the same time, the stronger trough over eastern Colorado will continue to track east-southeast toward eastern Tennessee.  This stronger tough will continue to strengthen over the next 48 hours and help to draw even more warm, moist air northward into the storm.  The interaction of the two troughs will help to generate a very strong low-pressure system at the surface that will further enhance the precipitation in the vicinity of the Delmarva Peninsula (general area of Washington D.C.).  Just north and west of the eventual track of the surface low will receive a prolonged period of very heavy snow that will allow for accumulation of up to 24-30″ in some areas.  Furthermore, as the two upper-level lows (shortwave troughs) continue to interact with each other, and the surface low moves over the warm waters of the gulf stream current, the low should continue to strengthen.  As the low does this, very strong northeast winds will develop along the coast (hence where we get the name ‘Noreaster’) and blizzard like conditions will be possible.  In fact, portions of New Jersey already have Blizzard Warnings in effect for this potential!

People in the Washington D.C. area are hopefully prepared for a winter storm that could potentially shut down the city through the weekend.  Some good-natured citizen has created a “snowpocalypse” website for Washington D. C. residents to gain the latest information.  So, as a public service for those who might be affected by the east coast winter storm, please visit http://snowpocalypsedc.com/for the latest information.

*Vorticity is a mathematical quantity used to quantify the potential for an air molecule to exhibit ’spin’.  Over simplifying this complex phenomenon, where ’spin’ is being blow toward tends to experience rising motion and wherever the ’spin’ is blowing from tends to experience sinking motion.

Above is a computer generated forecast for Tuesday morning (6 AM CST) 9 February 2010.  This forecast comes from the Global Forecast System (GFS) model and is used by meteorologists around the world to help predict the weather.  It is run 4 times a day (00Z, 06Z, 12Z, 18Z — 6 PM CST, 12 AM CST, 6 AM CST, 12 PM CST) and goes 384 hours into the future.  Now, as the forecast goes farther into the future the less accurate it tends to be.  This is why you will hardly ever see a meteorologists make a 384 hour prediction.  Often times something that is seen in the later parts of a forecast run (200+ hours into the future) will change from run to run.  This means that a major snow storm forecast at hour 288 might not be there on the next run.

If the forecasts are so unreliable that far into the future, then why do the models run that far into the future?  Well, the short answer is that while the exact details may change, often a pattern will emerge and you can get a big picture idea of what may happen in the future.  Take the above forecast image (valid 216 hours into the future).  The green on the map is areas where the model is predicting precipitation and areas to the north of the blue ‘0′ line are places that are forecast to be below freezing.  Based on this forecast, a meteorologist might make a prediction that there is a chance of snow in northeast Oklahoma, SW Missouri, and NW Arkansas.  However, being so far into the future, that is not a good idea.

What a good meteorologist should take from this image (and the entire forecast) is that the model is forecasting cold air to come southward out of Canada into the southern plains sometime next week.  Furthermore, the model is predicting some precipitation mechanism to develop in the southern plains / Gulf Coast around the same time.  Now, will this occur at 12Z (6 AM CST) on 9 February?  It’s too far out into the future to know for sure.   If several model forecasts in a row try to develop a storm on 9 February 2010, then a meteorologist would have more confidence that will happen.  If the model continues to change the date and time of when this might occur, a good forecaster will refrain from making a specific prediction about where and when, but understand that ingredients are coming together for a possible winter storm.

As for what the models are currently forecasting?  Well, I wouldn’t put too much stock in the exact timing of things, however, several models are forecasting cold air to move south from Canada.  At the same time, the models continue to have cyclones (lows) move across northern Mexico or southern Texas into the southeast United States.  The cyclones will provide a source of lift for the atmosphere and help to bring moisture from the Gulf of Mexico northward into the southern United States.  Add in the cold air from Canada, and the models are hinting at the potential for more winter storms in the coming weeks.  It’s far too early to tell where and when and how much.  However, it isn’t too soon to begin paying attention to forecasts for next week and beyond.  A lot can (and probably will) change in the coming days, so stay tuned!

After several days of more technical discussions, tonight we’ll tone it down a bit.

The winter storm that has blanked much of the Texas Panhandle, Oklahoma, and western Arkansas with a coat of ice, sleet, and snow is slowly moving east.  The graphic above displays all valid warnings.  Notice all the hot pink in the south?  Those are current winter storm warnings associated with the shortwave trough we’ve discussed this week.  Last night, the hot pink extended west into eastern New Mexico, and tonight it extends to the Atlantic Ocean.  This will certainly be a storm that is talked about for years!

As for where I live?  I received 1″ of glaze ice on the windward side of objects and 0.25″ of glaze ice on the leeward side of objects (freezing rain), 1″ of sleet, and 6-7″ of snow.  A taste of just about every form of winter precipitation!