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Tropical Storm WILMA (Text)

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TROPICAL STORM WILMA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT MON OCT 17 2005
 
A TREMENDOUS BURST OF DEEP CONVECTION...WITH TOPS AS COLD AS -87C TO
-89C... HAS DEVELOPED DURING THE PAST 6 HOURS NEAR AND TO THE SOUTH
AND SOUTHWEST OF THE ALLEGED CENTER OF NOW TROPICAL STORM WILMA.
MICROWAVE SATELLITE DATA ALONG WITH WIND DATA FROM NOAA BUOY 42057
INDICATE THAT THE CYCLONE HAS BEEN MOVING SLOWLY SOUTH OR
SOUTHWESTWARD. HOWEVER... THE LOW-LEVEL CENTER DOES NOT APPEAR TO
BE LOCATED IN THE CENTER OF THE DEEP CONVECTION... RATHER IT IS
LIKELY LOCATED NEAR THE NORTHEASTERN EDGE OF THE -50C CLOUD TOPS.
SATELLITE INTENSITY ESTIMATES ARE A CONSENSUS T2.5 FROM TAFB...
SAB...AND AFWA... AND A UW-CIMSS 3-HR AVERAGE ODT INTENSITY
ESTIMATE AT 17/0545Z WAS T2.8/41 KT. IN ADDITION... GRADIENT WIND
CALCULATIONS USING THE CENTRAL PRESSURE AND NEARBY PRESSURE VALUES
FROM THE NOAA BUOY AND JAMAICA SUPPORT 35-KT WINDS SOMEWHERE WITHIN
60 NMI OF THE CENTER. IF ANY 35-KT WINDS EXISTS... THEN THEY ARE
LIKELY IN THE SOUTHWESTERN QUADRANT WHERE THE STRONG CONVECTION IS
LOCATED. THEREFORE... THE INITIAL INTENSITY IS SET AT 35 KT...
WHICH MAKES WILMA THE 21ST NAMED TROPICAL STORM OF THE VERY BUSY
2005 ATLANTIC HURRICANE SEASON. THIS TIES THE RECORD SET BACK IN
1933.
 
THE INITIAL MOTION IS AN UNCERTAIN 235/03. THE GENERAL TREND IN THE
CONVECTIVE CLOUD PATTERN HAS BEEN TO SHIFT SLOWLY SOUTH OR
SOUTHWESTWARD AS MID-LEVEL RIDGING TO THE NORTH OVER FLORIDA AND
CUBA APPEAR TO BE THE ONLY STEERING FLOW AVAILABLE. BUT ON A LARGER
SCALE... WILMA REMAINS TRAPPED BETWEEN TO HIGH PRESSURE CELLS TO
THE NORTHWEST AND EAST OF THE CYCLONE. THE 00Z GLOBAL MODELS AND
THE MAJORITY OF THE NHC MODEL GUIDANCE HAS SHIFTED SIGNIFICANTLY
WESTWARD OR TO THE LEFT OF THE PREVIOUS GUIDANCE AND FORECAST
TRACK. THE ONLY MODELS NOT CLOSE TO THE NHC CONSENSUS OR GUNA MODEL
ARE THE ECMWF... CANADIAN... AND THE GFS 10-MEMBER ENSEMBLE MODELS.
THE ECWMF HAS BEEN REMARKABLY CONSISTENT WITH ITS TRACK THE PAST 5
DAYS IN MOVING THE CYCLONE TOWARD THE YUCATAN CHANNEL. IT ALSO WAS
THE ONLY MODEL TO EARLY AND ACCURATELY PREDICT CYCLOGENESIS. THE
ECMWF AND THE CANADIAN MODELS ARE ALSO THE ONLY MODELS THAT DO NOT
LOSE THE SHORTWAVE TROUGH LOCATED OVER THE CENTRAL U.S. THAT IS
CURRENTLY MOVING EASTWARD THROUGH THE AXIS OF THE LONGWAVE RIDGE.
UPPER-AIR DATA AT 00Z INDICATE A GOOD THERMAL PATTERN ASSOCIATED
WITH THIS TROUGH... WHICH ONLY THE ECMWF AND CANADIAN HAVE PICKED
UP ON. THE SHORTWAVE IS FORECAST TO DIG SOUTHEASTWARD DOWN THE EAST
SIDE OF THE LONGWAVE RIDGE AND GRADUALLY WEAKEN/ERODE THE
SUBTROPICAL RIDGE ACROSS FLORIDA... CUBA...AND THE EASTERN GULF OF
MEXICO BY 48 HOURS. ALSO... THE DEEP-LAYER LOW OFF THE COAST OF
BAJA CALIFORNIA IN COMBINATION WITH THE DEEP LOW OVER THE CANADIAN
MARITIMES SHOULD HELP MAINTAIN A BLOCKING-TYPE PATTERN ACROSS THE
U.S.... WHICH MEANS THE STEERING FLOW SHOULD CHANGE LITTLE FOR AT
LEAST THE NEXT 2-3 DAYS. THE OFFICIAL FORECAST TRACK WAS ONLY
SHIFTED SLIGHTLY TO THE LEFT... OR WEST... OF THE PREVIOUS TRACK
OUT OF RESPECT FOR THE CONSISTENT ECMWF MODEL... AND ALSO UNTIL THE
EVOLUTION OF THE SHORTWAVE TROUGH OVER THE CENTRAL U.S. BECOMES
MORE CERTAIN BY LATER TODAY OR TONIGHT.
 
SOME MID-LEVEL DRY AIR AND SHEAR ARE STILL UNDERCUTTING THE
IMPRESSIVE UPPER-LEVEL OUTFLOW PATTERN. HOWEVER... THESE ADVERSE
CONDITIONS APPEAR TO BE SLOWLY DIMINISHING BASED ON CONVENTIONAL
WATER VAPOR IMAGERY AND A 17/0155Z SSMI WATER VAPOR ANALYSIS.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN VERY FAVORABLE FOR
CONTINUED INTENSIFICATION THROUGHOUT THE FORECAST PERIOD. ONLY
POSSIBLE LAND INTERACTION WITH THE NORTHEASTERN YUCATAN PRECLUDES
FORECASTING WILMA TO BECOME A MAJOR HURRICANE BY 120 HOURS. THE
OFFICIAL INTENSITY FORECAST IS A BLEND OF THE LESS ROBUST SHIPS
MODEL AND THE VERY BULLISH GFDL MODEL... WITH THE LATTER MODEL
MAKING WILMA A 109-KT HURRICANE BY 60 HOURS.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0900Z 17.2N  79.7W    35 KT
 12HR VT     17/1800Z 17.1N  80.3W    40 KT
 24HR VT     18/0600Z 17.2N  81.1W    50 KT
 36HR VT     18/1800Z 17.4N  82.0W    60 KT
 48HR VT     19/0600Z 17.8N  83.3W    70 KT
 72HR VT     20/0600Z 18.5N  85.0W    80 KT
 96HR VT     21/0600Z 20.0N  86.5W    90 KT...NEAR NORTHEAST YUCATAN
120HR VT     22/0600Z 22.5N  87.5W    90 KT...NEAR NORTHEAST YUCATAN
 
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