If you're like me, it's not winter until it gets COLD. Last winter was one of those, mild with no real shots of cold weather. If you don't like winter or cold weather, close your eyes for a moment and savor those memories from last year... then back to reality as we look ahead. Winter is FAR from over and as far as we're concerned, it begins in about two weeks or so.
I wish I could come up with dramatic ways to say we're going to get cold, but since we're 2-3 weeks away, I have a little time to pick the best words. But it's going to get cold, plain and simple. The arctic air that's been bottled up in Alaska and Canada is about to take a trip south and make some dramatic changes to our weather here. Here's why.
In my last few blog posts, I've talk about several weather indices as well as changes that are occurring in the upper levels of the atmosphere. I'll try to piece all of that together so it make some sense.
Sudden Stratospheric Warming (SSW)
The first thing I'll discuss is the Sudden Stratospheric Warming or SSW. I talked about this in my last post and alluded to the fact that this was going to occur and would be a Major SSW, and this IS occurring right now. There is still a lot of research being done on SSW's and the study of how the upper levels of the atmosphere play an important part in what happens to our weather at the surface. But what we do know is that these type of events have direct correlations with blocking patterns and temperatures. In this case, it appears the SSW will be to be the kicker to get the cold air to start moving our direction.
As of this morning, the 10hPA temperatures have risen more than 40ºC (from ~-80C) and the zonal winds have decreased from ~80 m/sec to almost zero with a reversal expected to take place. Click this link to view the temps and winds in the stratosphere. If you click through the 10hPA images, you'll see a total split of the stratospheric polar vortex by 72 hours. This also occurs at the 30hPA level even sooner.
These changes are important and imply that this is a Major SSW and we haven't had one of those in several years. Here's an Abstract from a paper on SSW's
"The dynamics of the stratosphere sudden warming phenomenon is discussed in terms of the interaction of vertically propagating planetary waves with zonal winds. If global-scale disturbances are generated in the troposphere, they propagate upward into the stratosphere, where the waves act to decelerate the polar night jet through the induction of a meridional circulation. Thus, the distortion and the break-down of the polar vortex occur. If the disturbance is intense and persists, the westerly jet may eventually disappear and an easterly wind may replace it. Then “critical layer interaction” takes place. Further intensification of the easterly wind and rapid warming of the polar air are expected to occur as well as weakening of the disturbance. The model is verified by numerical integrations of the adiabatic-geostrophic potential vorticity equation. Computed results possess features similar to those observed in sudden warming phenomena."
One important thing to note... since the stratosphere has warmed almost 100 degrees, there is a corresponding drop in temperatures at lower levels and this has important implications for temperatures at the surface. I wanted to share this link, it shows through time-lapse animations, the process of SSW and how the polar vortex breaks down. Very cool.
Blocking Patterns
The next piece is are the blocking patterns that need to be in place in order to get the cold air here. Specifically, we're looking at three patterns, the Arctic Oscillation (AO), the North American Oscillation (NAO) and the Eastern Pacific Oscillation (EPO). For us, it's a matter of having the right combination of blocking to squeeze the cold air south instead of allowing it to slide east and north.
The models have been hinting about a negative NAO and EPO for a few weeks now. One of the issues we've had so far this winter has been the active upper air pattern that has brought air that originated over the Pacific Ocean. While that was good for rainfall, it prevented any real cold air to penetrate south. That pattern had to do with a EPO+ or positive EPO. That's all getting ready to change with the EPO forecasted to go negative shortly. A EPO- brings a nice blocking ridge of high pressure over the Pacific, effectively blocking that warm moist air from moving this way, and providing a barrier that keeps the cold air channeled within the continental US.
In order to channel cold air our way, the AO and NAO need to be in a negative state, and both models are forecasting some very negative states toward the end of the month. Blocking created by NAO- will force the winter storm tracks as well as cold, south instead of the zonal (east-west) flow that we've had for most of this winter.
So what does all of this mean?
There is a lag between what happens in the stratosphere and what we see on the ground,,, roughly two weeks or so. The blocking that will accompany the effects of the SSW is also about that far off. So we're looking at about 2 weeks or so before we experience any of these changes. We will have a period of mild weather between now and then, and then the vodka cold arrives (it's been -60ºF in Russia this winter). At this point it's anyone's guess as to how cold, but meteorologist have been saying the coldest air in more than two years will be coming. Right now expect the last week or so of January, and possibly the whole month of February, to be well below normal for temperatures... and possibly above normal for winter precipitation.
Hold on to your hats! This is going to be fun!
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At the 1-5hPa level, we are approaching some of the warmest temperatures we've seen in a SSW event. Winds at 1 hpa down to almost 10 hPa have completely reversed and are now moving west at 60-70 mph, a very substantial increase in speed from a day or two ago. One thing I also noticed was the lower level temperatures. They are compressed so you might miss it, but notice how they are now trending down all all the lower levels. This appears to be a long duration SSW which will help to keep the PV shredded and displaced. Substantial top down blocking will most likely begin occurring very soon. http://www.daculawea...time_series.php http://www.daculawea...rat_details.php - Look at the JFM images on this.
You'll notice I try to give credibility to what I write here by having facts and other corroborating data and meteorologist to back it up. What you'll hear from me you'll most likely hear first. Not bragging but very few public weather sites go past 3-5 days in a forecast. The Euro model has an accuracy of about 75% at 7 days. Most sites would lose credibility with those %'s (meteorologist already get a bad rap on this). So yes, they see it but don't talk too much about it. I've been doing a lot of research on SSW events, and this event we are having right now, will have MAJOR implications in just a couple of weeks. Look for the initial shot of Arctic air next week, and other deeper waves the following week. If anyone is majorly interested in the weather, I highly encourage you to visit http://www.americanwx.com/bb/index.php The best site to get the inside information about the weather. Right now there are 541 people online and out of those, more than 20 are meteorologist. During bad weather, you'll find meteorologist from all branches of the NWS, SPC, HPC, NCEP, as well as local NWS mets and TV meteorologist. Each has their own unique insight to the weather.
http://www.americanwx.com/bb/index.php/topic/38766-january-pattern-and-storm-discussion-ii I think you have to joint to see images.
Yea... real weather geeky stuff. :-)
30-HPA ANALYSIS 1200UTC 09 JAN 1. COLD MINUS 77 58N 102W, COLD MINUS 73 50N 52E, WARM MINUS 32 65N 138E, LOW 220 68N 92W, LOW 233 60N 77E, HIGH 370 48N 168W. 2. CONDITIONS AT 30-HPA HEIGHT FIELD, POLAR VORTEX SPLIT INTO TWO OVER NORTHERN CANADA AND OVER WESTERN SIBERIA. COLD AIR LIES OVER NORTHERN CANADA AND NEAR WESTERN RUSSIA. WARM AIR LIES OVER EASTERN SIBERIA. IN THE ZONAL MEAN FIELD, EASTERLY WIND IS OBSERVED THROUGHOUT THE STRATOSHPHERE OVER THE POLAR REGION. 3. STRATALERT EXISTS. MAJOR WARMING HAS CONTINUED AT 30-HPA. TEMPERATURE NEAR THE ARCTIC COAST OF CENTRAL SIBERIA INCREASED WITH MAXIMUM 38 DEGREES FROM 2 JAN TO 9 JAN 2013. REMARK: THE HEIGHT DATA SHOULD BE READ IN DECAMETERS ADDING 20 KILOMETERS.
These changes are already starting to be felt at the surface. Greenland had warmed up some earlier in the winter but currently this morning, there are two places, Neem and Summit Greenland, that are at -58ºF below zero. The models are becoming more insistent with the cold air, but right now they're having a difficult time latching on to solutions. Expect to see wild fluctuations over the next week or so until the chaos created by the strat warming has calmed down. I'll have more on this later this morning.
NWS Blacksburg - http://www.daculaweather.com/4_afd_rnk.php "So for today...break out the T-shirts...shorts...suntan lotion and the likes and enjoy a taste of Florida like weather. Grill a few dogs/burgers/steaks on the grill and soak it up. Kick the kids out doors for the afternoon and raise the windows. What I am really trying to get at...is just get out and enjoy the day...because if you don't...you’re going to miss the middle winter tropical cruise. After today...it’s all downhill. " And this: "AFTER NEXT WEEKEND GONNA TURN OUR ATTENTION TO THE SPLIT POLAR VORTEX...HALF OF WHICH IS GOING TO BE SETTLING SOUTH OVER CENTRAL AND EASTERN CANADA. THIS FEATURE IS POISED TO MAKE A BRUTAL APPEARANCE AFTER THE HOLIDAY WEEKEND WITH AN ARCTIC FRONT PLOWING SOUTHBOUND THROUGH THE EASTERN CONUS JANUARY 21-22 TIMEFRAME. THE AIRMASS ASSOCIATED WITH THIS FEATURE PROMISES TO BRING THE COLDEST WEATHER TO OUR AREA THAT WE HAVE CERTAINLY SEEN THIS WINTER...AND LAST WINTER TOO."
You know Tommy, I've loved this since I was a kid. I think I missed my calling in life! All of the higher level math probably would have been my downfall though! Here's an excerpt from the latest medium range forecast from the HPC this morning: http://www.daculaweather.com/4_hpc_extended_disco.php EXTENDED FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD 1245 AM EST SUN JAN 13 2013 VALID 12Z WED JAN 16 2013 - 12Z SUN JAN 20 2013 THE HPC MEDIUM RANGE FORECAST REMAINS STEADFAST DESPITE THE MANY OFF-KEY VOICES FROM THE PEANUT GALLERY OF DETERMINISTIC MODELS. A COLD/DRY AIRMASS SHOULD OVERTAKE MUCH OF THE CONUS EAST OF THE DIVIDE AND NORTH OF THE GULF AS ANOTHER NORTHERN SHORTWAVE TUGS THE CANADIAN VORTEX TOWARD THE GREAT LAKES. BOTH THE GFS AND ECMWF INDICATE THIS SECOND SURGE THROUGH CANADA THOUGH WITH SOME EXPECTED DIFFERENCES. IF NOTHING ELSE... IT WILL AT LEAST FEEL MORE LIKE WINTER IN THE EAST THOUGH QPF POTENTIAL WILL BE LIMITED TO THE NORTHER PLAINS/GREAT LAKES AND SOUTHEAST/FLORIDA.
"Looking toward next week weekend, a brief warm up appears somewhat likely across the Southern Plains before all eyes turn to our N during the latter half of the weekend. The Euro is suggesting a very potent Arctic Air mass with a 1058mb Arctic High dropping S into the Plains along the lee side of the Rockies while the GFS is a bit weaker with the high pressure, but has not been consistent and continues to struggle with the evolving pattern. Both global models and their ensembles are suggesting the Polar Vortex will drop well S into the Great Lakes region as heights build across the Pacific into Alaska and a deep trough develops E of the Continental Divide. The European suite of ensembles and operational guidance has been rather consistent in developing a potential Arctic Outbreak early next week, so it will bear watching in the coming days exactly how things unfold. As we can see, the forecast is extremely tricky and has major implication on the sensible weather we can expect this week on into the early next week time frame."
It appears the 1 hPa down to 5 hPa have stopped warming and reversed a few degrees down. However, the warming is propagating downward as all of the lower levels are still warming. This first row of links are what you would view here: http://www.daculaweather.com/4_strat_temp_time_series.php The 2nd row (JFM) and the "N"'s are what we're looking at here: http://www.daculaweather.com/4_strat_details.php
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD 1004 AM EST SUN JAN 13 2013 VALID 12Z WED JAN 16 2013 - 12Z SUN JAN 20 2013 REVERTED BACK TO MOSTLY THE ENSEMBLE MEAN, IN THIS CASE THE 00Z/13 ECENS MEAN, FOR THE NEW MEDIUM RANGE PACKAGE. YESTERDAY, THE DETERMINISTIC ECMWF WAS IN ENOUGH HARMONY WITH ITS MEAN TO BE RELIABLE THROUGH AT LEAST MID PERIOD; BUT TODAY, THE 00Z/13 DETERMINISTIC ECMWF WAS SUFFICIENTLY OUT OF SYNC WITH THE MEAN, PARTICULARLY IN THE NORTHERN STREAM, TO PRECLUDE ITS INCORPORATION. THERE HAS BEEN EVEN MORE VOLATILITY RUN-TO-RUN WITH THE GFS SOLUTIONS. THE BIG PICTURE STILL FEATURES A GRADUAL INVASION OF ARCTIC AIR INTO THE CONTIGUOUS UNITED STATES EAST OF THE CONTINENTAL DIVIDE, WITH DRY CONDITIONS OVER THE WEST. STILL WATCHING A POSSIBLE WAVE EMERGING FROM THE GULF STATES DAY 5 WHICH COULD SEND A ROUND OF RAIN, ICE, AND SNOW THROUGH PARTS OF THE EAST. CISCO
NATIONAL WEATHER SERVICE PEACHTREE CITY GA 1031 AM EST MON JAN 14 2013 ...FLOOD WATCH IN EFFECT THROUGH WEDNESDAY MORNING... THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS EXPANDED THE • FLOOD WATCH TO INCLUDE PORTIONS OF NORTH GEORGIA... MAINLY ALONG AND NORTH OF A CARROLLTON TO ATLANTA TO JEFFERSON LINE. • THROUGH WEDNESDAY MORNING. • WIDESPREAD SHOWERS WITH PERIODS OF HEAVY RAIN WILL OCCUR OVER THE WATCH AREA. ONE TO TWO INCHES HAVE ALREADY FALLEN MAINLY NORTH OF A CARROLLTON TO CANTON TO CLEVELAND LINE. ADDITIONAL RAINFALL AMOUNTS OF 2 TO 3 INCHES CAN BE EXPECTED. THIS WILL ALLOW FOR POTENTIAL STORM TOTALS OF 3 TO 4 INCHES WITH ISOLATED AMOUNTS UP TO 5 INCHES. • SOILS ARE WET IN NORTH GEORGIA DUE TO RECENT RAINFALL. THIS WILL HELP IN PRODUCING RUNOFF AS THE RAINFALL AMOUNTS BEGIN TO ACCUMULATE THROUGH LATE TUESDAY NIGHT. MINOR FLOODING OF SMALLER CREEKS...STREAMS...AND LOW- LYING FLOOD PRONE AREAS WILL BE POSSIBLE. BIG CREEK...NANCY CREEK...SUWANEE CREEK...AND PEACHTREE CREEK SHOULD BE MONITORED CLOSELY. PRECAUTIONARY/PREPAREDNESS ACTIONS... A FLOOD WATCH MEANS THERE IS A POTENTIAL FOR FLOODING BASED ON CURRENT FORECASTS. YOU SHOULD MONITOR LATER FORECASTS AND BE ALERT FOR POSSIBLE FLOOD WARNINGS. THOSE LIVING IN AREAS PRONE TO FLOODING SHOULD BE PREPARED TO TAKE ACTION SHOULD FLOODING DEVELOP.
http://www.daculaweather.com/images/2013_01/snow.gif
The page it came from can be found here: http://www.daculaweather.com/current/misc/google-maps-radar/4_google_radar.php
SO FAR...THE FZG RAIN IS PRIMARILY COATING TREES AND POWERLINES (AS EXPECTED CONSIDERING THE RECORD WARMTH WE SAW LATE LAST WEEK AND OVER THE WEEKEND HELPING KEEP ROAD SFCS WARM ENOUGH TO PREVENT ICING). WE HAD PREVIOUSLY ANTICIPATED THAT RAIN/FZG RAIN WOULD PERIODICALLY CHANGE BACK AND FORTH DUE TO LATENT HEAT RELEASE AS SFC FZG OCCURRED...BUT COLD ADVECTION HAS BEEN QUITE STRONG THROUGH THE DAY. THIS HAS ALLOWED FOR MORE WIDESPREAD GLAZING PROBLEMS ACROSS THE CWA ON THOSE ELEVATED SURFACES. ONE CONCERN FOR THE NEXT SEVERAL HOURS IS A BOUNDARY LINE SHOWING UP ON GWX RADAR. DUAL POL ANALYSIS INDICATES THAT THIS LINE (CURRENTLY EXTENDING FROM NASHVILLE TO OXFORD) MAY BE INDICATING A REINFORCING SHOT OF COLD AIR HEADED TOWARD THE CWA. FOR THIS REASON...WE WILL NEED TO BE MONITORING THE TEMPERATURE TRENDS THIS EVENING CLOSELY. IF TEMPERATURES DO NOT START TO RECOVER SLIGHTLY WE MAY NEED TO BE CONCERNED ABOUT ICE ACCUMULATIONS RISING TOWARD OR ABOVE THE ONE QUARTER INCH MARK BY THE EARLY MORNING HOURS.
THE ARCTIC FRONT RESPONSIBLE FOR BRINGING IN MUCH COLDER TEMPERATURES SHOULD BE WORKING THROUGH THE EASTERN CONUS THROUGH THE MEDIUM RANGE... A RESULT OF ENERGY ROTATING UNDER/TROUGH THE VORTEX... BUT THE 18Z GFS WAS MORE AGGRESSIVE WITH ITS COLD PUSH THAN THE ECMWF SO A COMPROMISE SOLUTION... TEMPERED BY THE 12Z/14 ECMWF ENSEMBLE MEAN... SERVED BEST. WITH A NW FLOW OUT OF CANADA THE CONTINENTAL DIVIDE SHOULD GENERALLY BE THE BARRIER TO THE WEST FOR THE COLDEST AIR THOUGH THE ECMWF HAS TRENDED WEST WITH ITS SHORTWAVE ENERGY DIVING SOUTHEASTWARD OUT OF CANADA OVER THE WEEKEND WHILE THE GFS FOCUSES ON A SOUTHWARD PUSH. AGAIN THE ENSEMBLE MEANS /BOTH THE ECMWF AND GEFS/ LIE IN BETWEEN. CAPITALIZED ON THE DECENT AGREEMENT BETWEEN THE GFS/ECMWF WITH THE ECMWF ENSEMBLE MEAN FOR THE FORECAST. SENSIBLE WEATHER... THE TEMPERATURE TREND EAST OF THE DIVIDE WILL BE DOWN NEARLY EVERYWHERE... WITH FLORIDA AND SOUTH TEXAS THE LAST HOLDOUTS AS THE ARCTIC FRONT PUSHES SOUTH AND EAST INTO EARLY NEXT WEEK. MOST LOCATIONS NORTH OF 30N SHOULD DIP BELOW FREEZING BY TUE/D7 WHILE SUBZERO TEMPERATURES SHOULD BE CONFINED TO THE DAKOTAS/MINNESOTA/WISCONSIN/MONTANA... AS WELL AS NORTHERN MAINE. THE WEST SHOULD BE NEAR TO ABOVE NORMAL EXCEPT IN THE MOUNTAIN LOCATIONS TRAPPED UNDER AN INVERSION.
"Just a heads up for you folks. Conditions are deteriorating quickly across N Central and E Texas this morning. Once again the models have under estimated the short wave progressing E across Northern Mexico and there are some indications that a negative tilted 5H low will develop that was not modeled. Just something to keep an eye on today. College Station in Northern SE Texas is reporting freezing rain at this hour as well."
...WINTER WEATHER POSSIBLE ACROSS NORTH GEORGIA ON THURSDAY... A STRONG LOW PRESSURE SYSTEM WILL MOVE ACROSS THE STATE ON THURSDAY. AHEAD OF THE SYSTEM... A DEEP SOUTHERLY FLOW WILL SPREAD AMPLE GULF MOISTURE NORTHWARD... RESULTING IN WIDESPREAD RAIN ACROSS NORTH AND CENTRAL GEORGIA. AS THE ASSOCIATED COLD FRONT PUSHES INTO THE CAROLINAS THURSDAY AFTERNOON... A DEEP COLD AIR MASS WILL BEGIN TO SPREAD INTO THE AREA FROM WEST TO EAST THURSDAY AFTERNOON AND EVENING. AS A RESULT... THERE IS A POTENTIAL FOR RAIN TO CHANGE OVER TO SNOW ACROSS PARTS OF NORTH GEORGIA IF SUFFICIENT WRAP AROUND MOISTURE CAN SPREAD BACK INTO THE COLD AIR MASS BEHIND THE DEPARTING COLD FRONT. DESPITE WARM GROUNDS FROM RECENT UNSEASONABLE WARM TEMPERATURES... THERE IS THE POTENTIAL THAT STRONG UPPER FORCING COULD ENHANCE SNOWFALL RATES ENOUGH TO ALLOW FOR SOME LIGHT SNOW ACCUMULATIONS ACROSS PARTS OF NORTH GEORGIA BY MID TO LATE THURSDAY AFTERNOON OR EARLY EVENING... BUT THIS WOULD BE MAINLY OVER ELEVATED AND GRASSY SURFACES. ALTHOUGH LIGHT SNOW COULD BE SEEN AS FAR SOUTH AS A LA GRANGE TO ATHENS LINE... IT APPEARS THE GREATER CHANCES FOR SNOW ACCUMULATION WOULD BE GENERALLY NORTH OF THE I-20 CORRIDOR WEST OF ATLANTA... AND THE I-85 CORRIDOR EAST OF ATLANTA.