Tropical Storm DOLLY

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TROPICAL STORM DOLLY SPECIAL DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042008
1145 AM EDT SUN JUL 20 2008
 
WE HAVE BEEN CLOSELY MONITORING THE STRONG TROPICAL WAVE AS IT HAS
CROSSED THE CARIBBEAN SEA DURING THE PAST FEW DAYS...WITH SEVERAL
AIRCRAFT RECONNAISSANCE MISSIONS SEARCHING FOR A WELL-DEFINED
CLOSED SURFACE CIRCULATION.  NOT UNTIL THIS MORNING DID THE
AIRCRAFT DETECT SUCH A CIRCULATION.  THE SYSTEM IS PRODUCING MORE
THAN ENOUGH DEEP CONVECTION REQUISITE OF A TROPICAL CYCLONE...SO
ADVISORIES ARE BEING INITIATED.  THIS SYSTEM HAS BEEN PRODUCING
WINDS OF 35-40 KT FOR THE PAST 24 HOURS OR SO...AND THIS MORNING
THE SFMR ON THE AIRCRAFT REPORTED WINDS AS STRONG AS 42 KT...ALONG
WITH WINDS OF 50 KT AT FLIGHT LEVEL.  IN ADDITION...NOAA BUOY
42057...SITUATED SOUTHEAST OF THE CIRCULATION CENTER...MEASURED
SUSTAINED WINDS OF TROPICAL STORM FORCE FOR ABOUT FOUR HOURS THIS
MORNING...AS STRONG AS 39 KT.  BASED ON THE ABOVE DATA...THE
CYCLONE IS IMMEDIATELY DESIGNATED A TROPICAL STORM WITH MAXIMUM
WINDS OF 40 KT.  THIS IS CURRENTLY A SPRAWLING SYSTEM WITH 34-KT
WINDS AND HEAVY RAINS EXTENDING WELL AWAY FROM THE CENTER...ALTHOUGH
VERY RECENTLY CONVECTION HAS BEGUN TO CONSOLIDATE OVER THE
CIRCULATION CENTER.

THE INITIAL MOTION ESTIMATE IS 305/15...WITH STEERING PROVIDED BY A
NARROW MID-LEVEL RIDGE ACROSS FLORIDA IN BETWEEN DOLLY AND
CRISTOBAL.  THAT RIDGE IS FORECAST BY THE GLOBAL MODELS TO
GRADUALLY WEAKEN AS A MID-LATITUDE TROUGH DEEPENS OVER THE GREAT
LAKES REGION.  AS A RESULT...THE FORWARD MOTION OF DOLLY IS LIKELY
TO BECOME SLOWER WHEN IT IS OVER THE GULF OF MEXICO.  THE MODELS
ARE IN GOOD AGREEMENT ON THE TRACK OVER NORTHERN YUCATAN AND THE
SOUTH-CENTRAL GULF DURING THE NEXT COUPLE OF DAYS...BUT THEN THE
SPREAD IS GREATER ON DAYS 3-5...WITH SOME MODELS EVENTUALLY
FORECASTING DOLLY TO MOVE INTO NORTHERN MEXICO...WHILE OTHERS HEAD
INTO SOUTHERN TEXAS.  THEY ALSO DISAGREE GREATLY ON HOW LONG IT
MIGHT TAKE FOR DOLLY TO MAKE FINAL LANDFALL.  THE MOST PRUDENT
APPROACH FOR NOW IS FOR THE OFFICIAL FORECAST TO BE VERY CLOSE TO
THE MODEL CONSENSUS.

THERE ARE TWO INHIBITING FACTORS FOR STRENGTHENING IN THE SHORT
TERM...WITH THE OBVIOUS ONE BEING INTERACTION WITH THE LAND MASS OF
YUCATAN TONIGHT.  ALSO...AN UPPER-LEVEL LOW IMMEDIATELY TO THE WEST
OF DOLLY IS IMPARTING SOME WIND SHEAR THAT IS PART OF THE REASON
FOR SUCH AN ASYMMETRIC CLOUD PATTERN.  THAT LOW...HOWEVER...IS
HEADED SOUTHWESTWARD AND OUT OF THE WAY...AND WHEN DOLLY REACHES
THE GULF OF MEXICO IT IS LIKELY TO FIND ITSELF BENEATH A LARGE
UPPER-LEVEL ANTICYCLONE...SO CONDITIONS APPEAR CONDUCIVE FOR
STRENGTHENING OVER THE VERY WARM GULF WATERS.  THE OFFICIAL
INTENSITY FORECAST IS CLOSE TO THE SHIPS MODEL SOLUTION OF A STRONG
TROPICAL STORM OVER THE WESTERN GULF...ALTHOUGH THE GFDL FORECAST
OF A HURRICANE IN THAT AREA IS CERTAINLY POSSIBLE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/1545Z 18.4N  84.2W    40 KT
 12HR VT     21/0000Z 19.7N  86.3W    45 KT
 24HR VT     21/1200Z 21.1N  89.5W    40 KT...INLAND OVER YUCATAN
 36HR VT     22/0000Z 22.2N  92.2W    45 KT...OVER GULF OF MEXICO
 48HR VT     22/1200Z 23.0N  94.0W    50 KT
 72HR VT     23/1200Z 24.5N  96.0W    55 KT
 96HR VT     24/1200Z 26.0N  97.5W    60 KT...INLAND
120HR VT     25/1200Z 27.0N 100.0W    35 KT...INLAND
 
$$
FORECASTER KNABB
 
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