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| #202033 (Received by flhurricane at: 12:23 PM 20.Jul.2008) TCDAT4 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 |
