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Kirk Mellish's Weather Commentary

Posted: 4:28 p.m. Thursday, Feb. 25, 2010

GFS3 model odd-man out but no gurantees 

By Kirk Mellish

I'll just cut and paste from what I put on my Atlanta Weather Examiner.com blog this morning:

Preliminary map for Tuesday Morning, slightly slower and further South than yesterdays expectation

Preliminary map for Tuesday Morning, slightly slower and further South than yesterdays expectation
HPC/NOAA/NWS

VALID 12Z MON MAR 01 2010 - 12Z THU MAR 04 2010

GFS3 out to lunch on next week weather threat in Gulf Coast states to VA, but way too soon to tell who will gets snow vs. rain, and how much of each will fall or where Tuesday-Wednesday. Storm could be a swing and a miss and North Georgia gets little or nothing at all, OR significant snow is either North of Georgia or SOUTH of Atlanta.

Here is some model output for the system next week for Atlanta liquid equivalent as of this writing:

Euro ENS 0.50-0.75
Euro OP .25-.50

JMA .10-.25

DEGEX 0.0

NOGAPS .25-.50

CMC .10-.25

GFS 0.0

UKMET shows storm no QPF available


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 CENTERS. 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.

THERE IS MUCH LESS AGREEMENT ON THE POTENTIAL FOR HEAVY SNOW IN THE LOWER MISSISSIPPI AND LOWER TENNESSEE VALLEYS FOR MONDAY INTO TUESDAY. THE PAST SEVERAL CYCLES OF THE GFS HAVE TAKEN THE FORECAST STORM FROM THE SOUTHERN PLAINS INTO THE CENTRAL/SOUTHERN GULF OF MEXICO WITH A DRIER FORECAST FOR THIS REGION. TODAY'S 00Z AND 12Z CMC AND ECWMF OPERATIONAL RUNS FOLLOW A TRACK CLOSER TO THE NORTHERN GULF AND BRING PRECIPITATION INTO THESE AREAS. HOWEVER, TODAY'S OPERATIONAL ECMWF THERMAL PROFILES WOULD SUPPORT A MIX OF RAIN/SNOW, WITH CMC'S MORE SUPPORTIVE OF AN ACCUMULATING SNOWFALL. GIVEN THE INCREASED UNCERTAINTY, THE AREA OF HEAVY SNOW ACROSS THESE REGIONS WAS REMOVED, BUT THIS AREA WILL NEED TO BE VERY CAREFULLY MONITORED WITH THE LATEST MODEL RUNS. IN THE LEAST, IF THE ECMWF AND/OR CMC SOLUTIONS ARE CORRECT, SLICK ROADS DUE TO A RAIN/SNOW MIX OR ACCUMULATING SNOWS WOULD BE EXPECTED ACROSS THESE AREAS.

THERE IS A POTENTIAL THREAT OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF CENTRAL AND SOUTHERN FLORIDA ALONG AND AHEAD OF THE SURFACE COLD FRONT ASSOCIATED WITH THIS SYSTEM.
 

Big storm on table from Texas to FL and VA early next week
But the devil is in the details and the details can't be worked out this far in advance.