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| #202241 (Received by flhurricane at: 11:08 AM 21.Jul.2008) TCDAT4 TROPICAL STORM DOLLY DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042008 1100 AM EDT MON JUL 21 2008 THERE IS LITTLE DOUBT NOW THAT DOLLY HAS A CLOSED SURFACE CIRCULATION...WHICH HAS BECOME EVIDENT IN VISIBLE SATELLITE IMAGERY OVER THE GULF OF MEXICO JUST OFF THE NORTHERN COAST OF THE YUCATAN PENINSULA. A NOAA RECONNAISSANCE AIRCRAFT RECENTLY CONFIRMED THE EXISTENCE OF THE CLOSED CIRCULATION IN THE LOW-LEVEL WIND FIELD...AND FOUND THAT MAXIMUM WINDS REMAIN ABOUT 45 KT. THE DEEP CONVECTION IS NOW STARTING TO WRAP AROUND THE WESTERN SIDE OF THE CIRCULATION...AND OUTFLOW CONTINUES TO EXPAND IN ALL QUADRANTS. A LARGE UPPER-LEVEL ANTICYCLONE COVERS MOST OF THE GULF OF MEXICO...SO THE ATMOSPHERIC ENVIRONMENT APPEARS QUITE CONDUCIVE FOR STRENGTHENING...AND THE SEA-SURFACE TEMPERATURES ALONG THE ENTIRE OVER-WATER FORECAST TRACK ARE QUITE WARM. IN ABOUT 18-24 HOURS...DOLLY IS EXPECTED TO PASS OVER SSTS GREATER THAN 29 CELSIUS...AND A RELATIVE MAXIMUM IN OCEAN HEAT CONTENT...AN AREA WITH A SOMEWHAT DEEPER RESERVOIR OF WARM WATER BENEATH THE SURFACE. AS A RESULT OF THESE CONDITIONS...STRENGTHENING APPEARS LIKELY...BUT GIVEN THE CURRENT SPRAWLING NATURE OF THE CIRCULATION...THE RATE OF INTENSIFICATION IS DIFFICULT TO FORECAST...SINCE IT IS UNCERTAIN HOW LONG IT WILL TAKE FOR A TRUE INNER CORE TO DEVELOP. THE NEW OFFICIAL FORECAST LEANS TOWARD THE HIGHER END OF THE INTENSITY GUIDANCE...CLOSE TO THE GFDL SOLUTION...IN CALLING FOR A SLIGHTLY HIGHER PEAK INTENSITY THAN THE PREVIOUS ADVISORY. SINCE THE EXACT TIMING AND LOCATION OF LANDFALL ARE UNCERTAIN...THE FORECAST WEAKENING BETWEEN 48 AND 72 HOURS ONLY RESULTS FROM THE 72-HOUR POINT BEING INLAND...AND A STRENGTHENING TREND IS FORECAST UP TO THE TIME OF FINAL LANDFALL. DOLLY IS STILL MOVING RATHER QUICKLY...300/16...TO THE SOUTH OF A MID-LEVEL RIDGE OVER THE SOUTHEASTERN UNITED STATES. ALL OF THE DYNAMICAL MODELS FORECAST THIS RIDGE TO GRADUALLY WEAKEN DURING THE NEXT FEW DAYS...RESULTING IN TRACK GUIDANCE SHOWING A SIGNIFICANT SLOWING OF THE FORWARD MOTION AS THE CYCLONE PROCEEDS INTO THE WESTERN GULF. MOST OF THE GUIDANCE HAS SHIFTED A LITTLE NORTHWARD OVER THE WESTERN GULF...AND SO HAS THE OFFICIAL FORECAST...WHICH REMAINS DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE. THERE ARE VERY RELIABLE MODELS ON BOTH SIDES OF THE OFFICIAL TRACK...SO IT IS IMPORTANT NOT TO FOCUS ON THE EXACT LOCATION OF LANDFALL IMPLIED BY THE OFFICIAL TRACK. THE NEW FORECAST REQUIRES THE ISSUANCE OF HURRICANE AND TROPICAL STORM WATCHES FOR THE COAST OF THE WESTERN GULF OF MEXICO. FORECAST POSITIONS AND MAX WINDS INITIAL 21/1500Z 22.1N 89.5W 45 KT 12HR VT 22/0000Z 23.0N 91.6W 55 KT 24HR VT 22/1200Z 24.2N 93.8W 60 KT 36HR VT 23/0000Z 25.1N 95.2W 70 KT 48HR VT 23/1200Z 25.9N 96.4W 80 KT 72HR VT 24/1200Z 26.5N 98.5W 50 KT...INLAND 96HR VT 25/1200Z 27.0N 100.5W 30 KT...INLAND 120HR VT 26/1200Z...DISSIPATED $$ FORECASTER KNABB |
