These links and facts are compiled by Aron Sterling of Fairfax County Public Schools, and the general information pertains to the Northern Virginia area. Many of the links will be helpful to all. Enjoy!

10/28/07

Hello Weather fans,

After a long, hard drought period we are ready to begin facing a changing environment for fall’s decent into winter.  You may have noticed the absolute lack of Weather Alerts due to the lack of change in weather, but this long period of silence has allowed me to study the winter weather data like never before.

First, let start with the Winter Weather advisory:

At 2pm the weather service in Sterling, Virginia issued a Frost Advisory for this area:  Here is that advisory:

...FROST ADVISORY REMAINS IN EFFECT FROM 3 AM TO 8 AM EDT

MONDAY...

A FROST ADVISORY REMAINS IN EFFECT FROM 3 AM TO 8 AM EDT MONDAY. COLD HIGH PRESSURE WILL BRING CLEAR SKIES AND LIGHT WINDS

BY TOMORROW MORNING. LOW TEMPERATURES WILL RANGE FROM THE LOWER TO MID 30S.

A FROST ADVISORY MEANS THAT FROST IS POSSIBLE. SENSITIVE OUTDOOR PLANTS MAY BE KILLED IF LEFT UNCOVERED.

While this seems like a minor thing, this change to colder weather will have an immediate impact on our students.  Remember that this has been a quick transition to cold and our bodies take time to acclimate to the new weather.  Tonight’s low will seem exceptionally cold to some, as will the early morning temperatures on Monday, Tuesday and Wednesday mornings.  Be prepared for students who are not sure whether to keep a jacket on or not and kids who seem to be underdressed, not to mention buildings that are colder as we need to change over to having the heat on.  With low temperatures only in the 60’s and the increasing angle of the sun’s rays, the outdoor temperatures will stay cool longer before warming up for short periods of time.  Please take personal care, as this is the time of year that we begin to see lots of tow trucks, as car batteries that are weak begin to stall out and tires react to the rapid contraction and expansion of air (though I have heard that the tires filled with nitrogen work better).

Winter Weather Prediction- Part #1

After reading and reading and reading, my winter weather prediction is mostly complete.  My data sources included NOAA forecasts, Ocean data, Observations of previous winters, data from natural resources and animals, almanacs and weather discussion boards.  Piecing all this information together is not an easy task, but the relative calm we experienced really helped give me time to do all this.

Here are the facts:

1.)  The main weather-maker for the US is the Pacific Ocean.  It is currently in the La Nina mode and strengthening.  La Nina is basically colder than normal temperatures found in the Pacific.  This makes the ocean more alive, but does produce some unusual weather across the country.  Luckily, La Nina events seem to follow a fairly consistent pattern (ok, consistent is a pretty strong word).  Usually for our area, a La Nina event will bring us below average snowfall and warmer than usual temperatures.  That is not to say that we cannot have significant snow storms.  In fact there have been two very significant snow storms late in the year during La Nina.  This is due to the fact that the other Ocean, the Atlantic, seems to change over its trend late in the season allowing a Nor’easter to develop.

2.)  The jet stream seems to be tilting in a sharper direction, which will produce unsettled weather above us and warmer than usual temperatures below us.  We, as usual, are on the line between, which means we observe more weather events around us, rather than through our area.

3.)  All discernable natural data (Wooly worms, trees, birds) seem to indicate a mild winter.  Now, not everyone places much stock in these bits of data, but as for me, of the American Indians place some level of reliability in these sources, so do I.

4.)  The Atlantic and other oscillations (these are tilts in temperature/pressure gradients and winds) seem to be a strong support for the La Nina to hold on and be uninterrupted for much of the winter.


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11/8/07

For those of you who want to experience some early-season snow, hang in there!

In any case, the La Nina effect seems to be right on track.  We are experiencing a normal fall and sliding into a start for winter.  By the way, we are expected to stay in a moderate La Nina pattern through December and the have it gradually ease.  This pattern is close to the 1996 La Nina event.  In 1996, the weakening of the La Nina was followed by a large Nor’easter and a late January storm with the largest snowfall for the DC area (28 inches on January 27-28).  In 2000, there was a storm with a foot of snow (more in Baltimore).  This also was during a weakening La Nina area.

I did want to return to the frost on the grass and cars, as it is often something younger students struggle to understand. Often elementary students believe that frost fell from the sky or that frost is caused from freezing of the object (grass or windshield).

Here is a great experiment to do with the kids to understand frost:

http://www.weatherwizkids.com/dew.htm

The Weather Savvy page has a good explanation, as well http://weathersavvy.com/Q-Winter_Frost.html

In addition, for those of you who are weather junkies:  An explanation of why frost forms faster on the windshield of your car than on the side windows!  http://www.newton.dep.anl.gov/askasci/gen01/gen01425.htm


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11/14/07

According to the weather service for tonight into tomorrow: 

EXPECT WIDESPREAD 0.50 TO 1.00 RAIN AMOUNTS ACROSS THE CWA (this is the weather advisory area).  

THAT MAY SUPPORT ISOLATED

THUNDER. GIVEN THE FORECAST VERTICAL PROFILES...CONVECTIVE ELEMENTS

WILL LIKELY BE LOW TOPPED IN NATURE AND WILL HAVE THE POTENTIAL TO

PRODUCE GUSTY WINDS. CONVECTIVE ELEMENTS MAY ALSO PRODUCE HEAVIER

RAINFALL AMOUNTS IN EXCESS OF AN INCH.

The update goes on to say:

THEN COLD ADVECTION IS STRONG ENOUGH TO PRODUCE FALLING TEMPERATURES BEHIND THE FRONT. IN ADDITION...COLD ADVECTION

WILL MIX DOWN POST-FRONTAL WINDS UP TO 30 KT. AS TEMPERATURES FALL DURING THE DAY...RAIN WILL MIX WITH/CHANGE TO SNOW 
ALONG/WEST OF THE ALLEGHENY FRONT WHICH WILL PAVE THE WAY FOR AN UPSLOPE SNOW EVENT AT THE BEGINNING OF THE LONG TERM. 
NEXT SIGNIFICANT

WX MAKER WILL BE AN UPSLOPE SNOW EVENT FOR AREAS ALONG AND WEST OF THE ALLEGANY FRONT. QUITE POSSIBLE TO RECEIVE SNOW 
ADVISORY AMOUNTS(1-4 INCHES) STARTING LATE THURSDAY AND LASTING INTO FRIDAY.

So, those of you driving from the far, far west… expect some snow!  For those of you wanting to see snow, head to the Alleganys!

But the rest of us… sadly….

MODELS DIVERGE ON MONDAY WITH THE EC TRACKING A FRONT ACROSS THE AREA WHILE THE GFS NOSES HIGH PRESSURE SOUTHWARD ALONG 
THE COAST AND THUS IS DRIER. WENT WITH THE GFS SOLUTION FOR MON-WED PERIOD WITH SFC HIGH TRACKING SLOWLY ACROSS AREA FOR 
THE PERIOD. THE EC IS NO LONGER ADVERTISING A COASTAL LOW FOR MONDAY NIGHT SO KEEPING A DRY FORECAST FOR EARLY NEXT WEEK.

L-  but you never know, huh???

In any case, tomorrow is going to be a good day to look at the weather with the students.  So, let’s get some weather links up that you can use:

http://www.erh.noaa.gov/lwx/  (our local weather office)

Check out WeatherBug Achieve’s information on the upcoming storms: http://achieve.weatherbug.com/HomepageArticles/WeatherNews/WeatherNewsCurrent.aspx

Weather Properties:  What makes Water so Special?  http://ga.water.usgs.gov/edu/waterproperties.html

Do a weather journal with students every morning!  http://cse.ssl.berkeley.edu/first/EyeontheSkyWeatherJournal/

Put the water vapor loop image up on the SMARTboard!  http://www.ametsoc.org/amsedu/dstreme/sat/smsat_wv_loop.gif

Practice reading the weather fronts: http://www.ametsoc.org/amsedu/dstreme/images/sfcumap.gif

Stay dry!!


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12/3/07
Looks like just a dusting for Wednesday.  L

311 PM EST MON DEC 3 2007

.SYNOPSIS...

-- Changed Discussion --

WINDY CONDITIONS WILL PERSIST THROUGH TONIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA TOMORROW ALLOWING FOR WINDS 
TO GRADUALLY LESSEN. A CLIPPER SYSTEM WILL BRING A DUSTING OF SNOW TO THE REGION WEDNESDAY. COLD HIGH PRESSURE WILL 
BUILD FOR THE END OF THE WEEK.

I will update you on Tuesday with the weather links for students to watch the weather come into the area.  But, check out this amazing water vapor loop… note the pressure system moving towards the east!

http://www.ssec.wisc.edu/data/east/animation/goeseastwv.html

Please note, mountain areas to the west will receive more snow.  Anyone traveling to the south towards Roanoke should not be overly concerned.  Tuesday evening travel should be alright, until the overnight time period lasting into the early morning of Wednesday.  If you travel during this time period you should check road hazards ahead of time and listen to weather radio during the drive.


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12/4/07

Ok, as the hours pass, the amount of uncertainty has grown as to the amount of snow and when it will begin.

As of right now, conditions exist for a snow-type of event.  Whether this is a dusting of snow, mostly Wednesday, or between 1-2 inches of snow, again mostly Wednesday, is yet to be seen.

The early morning run of the models showed that the western counties getting enough snow for a snow advisory category (2+ inches), and our area showing between 1 and 2 inches of snow.  The reason for this uncertainty is that the clipper system is in place, but a system coming from the Pacific Northwest is complicating the amount and type of moisture available.

So, bottom line is this (as of now):

Wednesday will be a bit more complex than we thought.  Worst case scenario is that snow begins to fall late Tuesday evening and then we have a very messy Wednesday.  I am thinking that since the 2 inch threshold of snow will be hard to come by, we will see messy roads at the worst and if it is only a dusting, slick roads, slowing down commutes.

I will update this as the day wears on…

But right now:

Chance of delay in the morning: 70%  The western areas should be the worst road conditions and will probably dictate this.

Chance of closure Wednesday: 30%  Again, if the system comes fast, dumps a bit more than projected and leaves, the clean up might take a bit longer than 10 AM….

So, start your dancing now!!

By the way, western areas that are closer to the mountains are projected in the 1-3 inch range, thus in the warning category.  Those going west, take care.  Those heading south, once out of the immediate area, will be just fine.

Weather links:

(Visual images and radars)

http://www.goes.noaa.gov/ECIR4.html

http://radar.weather.gov/radar.php?rid=lwx&product=N0R&overlay=11101111&loop=no

http://www.ametsoc.org/amsedu/dstreme/sat/smsat_ir_loop.gif

http://www.ametsoc.org/amsedu/dstreme/sat/smsat_wv_loop.gif

How does snow form? http://www.learner.org/interactives/weather/iceandsnow.html

Why is snow crunchy when you step on it? http://nsidc.org/snow/faq.html

General snow facts: http://www.rcn27.dial.pipex.com/cloudsrus/snow.html


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12/5/07 (1)

Good morning all,

The overnight shot of snow was from a separate system, so do not think that this pause is a sign of what is to come.

In fact, overnight the air seemed colder and there was more snow on surfaces than forecasters thought there would be.

Now, how about this… the 1-2” of snow for our area seem like a pretty sold bet.  In fact, the opposing computer model pushed us into the 2-4” category!

Look at the discussion from NWS in Sterling, Virginia:

THE GFS FORECASTED MORE SNOWFALL THAN THE NAM. FROM THE NAM...DENDRITIC GROWTH ZONE TECHNIQUES FORECASTED 2 TO 4 
INCHES WHILE MAX TEMP...SFC TEMP...10:1 AND QPF TECHNIQUES FORECASTED 1 TO 2 INCHES. ALL TECHNIQUES FROM THE GFS 
FAVORED 2 TO 4 INCHES. BELIEVE THE NAM IS MORE CLOSELY LINKED TO REALITY.

So, how about that?  Ok, back to reality…..

In all honesty, it appears we will have up to 2 inches of snow fall during the daytime hours until sometime around 8 pm.  Traffic, which was a bit dicey this morning, may be bad this afternoon.  Many main roads have been treated, so side roads remain the real issue.  How much will stick to roads is certainly debatable, but just know that the trip home may be a little longer than usual.

Have kids watch the snow come in…

Oh, a quick one.. very cute Discovery page on why snow is white: http://www.discovery.com/area/skinnyon/skinnyon971003/skinnyon.html

Visible radar: http://www.goes.noaa.gov/browse2.html

Animated radar loop: http://www.ametsoc.org/amsedu/dstreme/images/smrad_sum_loop.gif

The static water vapor image.  You can see the system from the Northwest merging with the existing front. http://www.goes.noaa.gov/browse3.html

The same water vapor, but in a loop: http://www.ametsoc.org/amsedu/dstreme/sat/smsat_wv_loop.gif

A good day to discuss condensation.  Here is a quick lesson plan from NOAA.  I love the fact about the amount of cloud droplets it takes to make one raindrop: http://www.srh.weather.gov/jetstream/atmos/ll_sweatin.htm

Wilson Bentley snowflake images: http://snowflakebentley.com/snowflakes.htm


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12/5/07 (2)

Now, think things are weird here?  There is a blizzard warning for Hawaii!  I am not kidding… check it out yourself… http://forecast.weather.gov/wwamap/wwatxtget.php?cwa=hfo&wwa=blizzard%20watch

A good thing to quiz older kids on… how would Hawaii have a blizzard?  J


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12/11/07

I cannot believe the talking heads!  Even focusing a second of attention on a system that is so far out is kind of silly.  All attention should be turned to our fellow citizens dealing the massive ice storms.  Kids out of school, no power, loss of life…this is the real weather story, as this type of storm may be more typical than not this winter.

To get some idea, check out the weather camera from Pleasant Hill, Iowa.  http://weatherbonk.com/weather/camDetail.jsp?id=_wc_1142897398192

The good news is that this ice storm is coming to an end.  Now, the repair needs to begin!

Ok, back to our area.  Here are the facts (not the spin from the talking heads to make you tune into them!).

Here is part of the discussion from the Weather Service:

So, basically, several of the computer models are in agreement that we will have a storm.  As far as a severe winter storm…. Who knows?  Weather cannot be predicted this far into the future, anyhow.

This will be an ever-changing forecast and really, we just do not know exactly what we will get.  This may be another “false alarm” for our area and a major storm racing up the east coast… or this may be a winter storm for our area with snow.

So, for those of you wanting an extended weekend… hope for a slowing system that arrives Saturday evening and snows steadily through Sunday afternoon.  This time period will put a premium on trying to plow before opening Monday.

Early starters, go ahead and start the snow dancing… but don’t get too serious about this just yet.

The rest of us… sit back and wait!  Why not watch some other weather cams?  Check them out: http://www.fcps.edu/ChesterbrookES/weathermapworld.htm

Oh, and what a start to wint… nope, winter has not even started yet!!!

Aron Sterling