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| #38982 (Received by flhurricane at: 10:31 PM 11.Aug.2005) TCDAT4 TROPICAL STORM IRENE DISCUSSION NUMBER 30 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT THU AUG 11 2005 OVER THE PAST SEVERAL HOURS....THERE HAS NOT BEEN MUCH CHANGE IN THE ORGANIZATION OF THE STORM AS SHOWN BY SATELLITE IMAGES. IRENE CONTINUES TO HAVE SOME BANDING FEATURES OVER ITS EASTERN SEMICIRCLE...BUT THE CLOUD TOPS ARE NOT VERY COLD AND THE DEEP CONVECTION ENCOMPASSES A RATHER SMALL AREA. DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB ARE UNCHANGED FROM THE PREVIOUS PACKAGE...SO THE CURRENT INTENSITY ESTIMATE REMAINS AT 45 KT. UPPER-LEVEL OUTFLOW OVER THE SOUTHEASTERN QUADRANT IS WEAK BUT APPEARS WELL-DEFINED OVER THE REMAINDER OF THE CIRCULATION. ACCORDING TO THE GLOBAL MODELS...IRENE WILL BE MOVING THROUGH AN ENVIRONMENT CHARACTERIZED BY ANTICYCLONIC UPPER-LEVEL FLOW AND WEAK VERTICAL SHEAR OVER THE FORECAST PERIOD. THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE SHIPS...GFDL...GFDN...AND THE FSU SUPERENSEMBLE GUIDANCE...ALL OF WHICH SHOW IRENE STRENGTHENING INTO A HURRICANE DURING THE NEXT COUPLE OF DAYS. LOCATING THE STORM CENTER REMAINS A CHALLENGE...ESPECIALLY WITH INFRARED IMAGERY. THUS THE INITIAL MOTION ESTIMATE...300/13...IS AN EDUCATED GUESS. NWP MODELS SHOW A 500 MB HIGH BUILDING NEAR BERMUDA DURING THE NEXT DAY OR TWO...AND THEN RETROGRADING WESTWARD LATER IN THE FORECAST PERIOD. AS IRENE APPROACHES THE RIDGE... STEERING CURRENTS ARE LIKELY TO WEAKEN...SO THE TROPICAL CYCLONE WILL LIKELY BE MOVING VERY SLOWLY IN 3 TO 5 DAYS. BEYOND 36 HOURS...THE TRACK MODEL GUIDANCE DIVERGES SIGNIFICANTLY. THE GFDL AND GFDN ARE NOW SHOWING A MORE WESTWARD TRACK AND ARE ON THE LEFT SIDE OF THE DYNAMICAL SUITE. THE U.K. MET OFFICE AND NOGAPS SOLUTIONS SHOW A NORTHWARD TURN...AS DOES THE GFS. HOWEVER THE LATTER MODEL ESSENTIALLY DISSIPATES THE TROPICAL CYCLONE BY THE END OF THE PERIOD. THE OFFICIAL FORECAST IS FAIRLY SIMILAR TO THE PREVIOUS ONE...AND ALSO SHOWS CONSIDERABLE SLOWING OF THE FORWARD SPEED BY 72 HOURS. THIS IS IN REASONABLE AGREEMENT WITH THE LATEST FSU SUPERENSEMBLE TRACK. FIVE-DAY TROPICAL CYCLONE FORECASTS HAVE CONSIDERABLE UNCERTAINTY IN BOTH LOCATION AND INTENSITY...SO IT IS STILL TOO EARLY TO TALK ABOUT SPECIFIC THREATS TO THE EAST COAST OF THE UNITED STATES. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 12/0300Z 26.4N 64.9W 45 KT 12HR VT 12/1200Z 27.3N 66.3W 50 KT 24HR VT 13/0000Z 28.3N 67.9W 55 KT 36HR VT 13/1200Z 29.0N 69.2W 60 KT 48HR VT 14/0000Z 29.8N 70.5W 65 KT 72HR VT 15/0000Z 31.5N 72.0W 70 KT 96HR VT 16/0000Z 33.0N 73.0W 75 KT 120HR VT 17/0000Z 35.0N 74.0W 75 KT |
