Chances increasing for Snowstorm Lower Mid-Atlantic States
Posted by
JAC on 2/26/2010, 7:37 am
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
219 PM EST THU FEB 25 2010
VALID 12Z SUN FEB 28 2010 - 12Z THU MAR 04 2010
...CHANCES INCREASING FOR A SNOWSTORM OVER THE LOWER MID ATLANTIC
STATES...
PRELIMINARY UPDATE...
USED THE 00Z/25 ECMWF TO UPDATE THE PRELIMINARY FRONTS AND
PRESSURES FOR DAYS 3-6 ACROSS THE NATION...WITH A MODEST
INCORPORATION OF THE ECENS MEAN DAY 7 TO MITIGATE THE UNCERTAINTY
IN SYNOPTIC DETAILS INHERENT TO THAT TIME RANGE. FOR THE SOUTH
AND EAST...THE MAJOR CONCERN IS THE WAVE THE MODELS TRACK ACROSS
THE GULF OF MEXICO...AND THEN OVER THE ATLANTIC OCEAN. THIS
WINTER SEASON HAS SEEN WAVE AFTER WAVE CROSS THE GULF OR DEEP
SOUTH...AND THEN TURN EITHER SUBTLY OR SHARPLY UP THE EASTERN
SEABOARD. IN MOST CASES...THE GLOBAL NUMERICAL MODELS HAVE BEEN
SHY ABOUT LIFTING THESE SYSTEMS FAR ENOUGH NORTH SEVERAL DAYS
OUT...WITH AN INEVITABLE CREEP NORTHWARD TOWARD CAPE HATTERAS WITH
TIME. THE SNOWFALL OVER MUCH OF THE SOUTHEAST A COUPLE WEEKS AGO
IS AN EXAMPLE OF SUCH A CASE...WITH MUCH OF THE GUIDANCE NOT
GIVING THE REGION ITS DUE UNTIL A MERE 36 HOURS FROM IMPACT. TOOK
THE CUE FOR THIS FORECAST...AND USED THE DETERMINISTIC
ECMWF...WHICH TRACKED CLOSEST TO THE COAST DAY 6. THIS MODEL HAS
THE SUPPORT OF THE GEM GLOBAL...AS WELL AS THE ENSEMBLE GUIDANCE
FROM BOTH THE EUROPEAN AND CANADIAN CENTRES. THE GFS AND ITS
ATTENDANT ENSEMBLE PACKAGE LOOKED FLAT BASED ON THE EXPERIENCE OF
THIS SEASON. THE WEST COAST WILL CONTINUE TO BE AT THE SPLITTING
POINT OF WAVES COMING IN FROM THE PACIFIC...WITH A COUPLE INTENSE
COLD MARITIME POLAR VORTICES SLATED FOR THE NORTHWEST DURING THE
SECOND HALF OF THE PERIOD. THE MIDDLE OF THE NATION WILL BE UNDER
THE INFLUENCE OF A CONTINUAL FEED OF CONTINENTAL POLAR AIR...THIS
REGIONS LOT IN LIFE IN THE TENACIOUS BLOCKING REGIME OF THE WINTER
OF 09-10.
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
355 AM EST FRI FEB 26 2010
VALID 12Z TUE MAR 02 2010 - 12Z FRI MAR 05 2010
MEDIUM RANGE GUIDANCE MAINTAINS A FAIRLY ENERGETIC PATTERN WITH
BUNDLES OF ERN PAC TROF ENERGY SEPARATING NEAR THE WEST COAST AS
THEY RUN INTO A PERSISTENT MEAN RIDGE OVER CANADA AND W-CNTRL
CONUS. THE LEADING SRN STREAM SYSTEM OF INTEREST IS FCST TO
TRAVEL FROM THE SRN PLAINS/WRN GULF COAST TO JUST OFF THE EAST
COAST IN THE MON-WED TIME FRAME. WHILE THERE IS SOME SPREAD WITH
THIS FEATURE... THE 00Z GFS AND GEFS MEAN ARE ON THE PROGRESSIVE
SIDE OF THE SPECTRUM WITH THE ECMWF/CMC/UKMET/NOGAPS AND 12Z ECMWF
ENSEMBLE MEAN ALL HOLDING THE SYSTEM CLOSER TO THE COAST BY LATE
DAY 5 WED. THIS SLOWER/WRN CLUSTER IS LIKELY BEST IN LIGHT OF THE
TENDENCY THIS SEASON FOR MODELS TO VERIFY TOO FAR SEWD SEVERAL
DAYS IN ADVANCE. ONE SIGNIFICANT WILD CARD IN THE EVOLUTION OF
THIS SYSTEM IS A BUNDLE OF ENERGY EXPECTED TO TRACK SEWD FROM THE
UPR MS VALLEY MON ONWARD. THUS FAR GUIDANCE HAS NOT BEEN
EXTREMELY AGREEABLE AMONG EACH OTHER AND COMPARED TO SUCCESSIVE
RUNS... BUT AT THE VERY LEAST THE LATEST ENSEMBLE GUIDANCE OFFERS
MORE SUPPORT FOR THE 00Z ECMWF WITH THIS FEATURE VERSUS THE
SLOW/DEEP OUTLIER SOLN OF THE 00Z GFS. |
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