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ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE GERT DISCUSSION NUMBER 19 NATIONAL WEATHER SERVICE MIAMI FL 11 PM EDT WED SEP 15 1999 THE SATELLITE PRESENTATION OF GERT IS NOT QUITE AS IMPRESSIVE THIS EVENING AS IT WAS THIS AFTERNOON. SATELLITE INTENSITY ESTIMATES AT 00Z WERE 127 AND 140 KT FROM TAFB AND SAB...BUT A RECENT 3 HR AVERAGE OF THE RAW OBJECTIVE DVORAK NUMBERS FROM THE UNIVERSITY OF WISCONSIN ALGORITHM WAS ABOUT 115 KT. FOR CONTINUITY...THE OFFICIAL INTENSITY IS HELD AT 130 KT FOR THIS PACKAGE. THE TRUTH WILL BE REVEALED LATER THIS MORNING WHEN A RECONNAISSANCE AIRCRAFT WILL BE IN THE CYCLONE. THE SHIPS INTENSITY FORECAST MODEL INDICATES SLIGHT WEAKENING OVER THE NEXT THREE DAYS...BUT GERT IS EXPECTED TO REMAIN A VERY POWERFUL HURRICANE. INITIAL MOTION IS 275/9...A BIT SLOWER THAN THE PREVIOUS ADVISORY. DROPSONDE DATA FROM THE NOAA GULFSTREAM JET NICELY SHOW THE MID- LEVEL SUBTROPICAL RIDGE NORTH OF THE HURRICANE. THE DATA ALSO SHOW A BREAK IN THE RIDGE ALONG 60W...AND MOST OF THE GUIDANCE INDICATES A TURN TO THE NORTHWEST BY THIS LONGITUDE. THE 18Z AVIATION HAS A HORRIBLE INITIALIZATION OF THE VORTEX REGION...WITH SOUTHEAST WINDS A FEW HUNDRED MILES AHEAD OF THE HURRICANE AT 500 MB THAT ARE 40-50 KT IN ERROR. THE OFFICIAL FORECAST IS IN CLOSE AGREEMENT WITH THE UKMET WHICH HAS PERFORMED WELL WITH THIS SYSTEM. FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 16/0300Z 17.9N 51.2W 130 KTS 12HR VT 16/1200Z 18.0N 52.5W 125 KTS 24HR VT 17/0000Z 18.4N 54.5W 120 KTS 36HR VT 17/1200Z 19.6N 56.6W 120 KTS 48HR VT 18/0000Z 21.0N 58.5W 115 KTS 72HR VT 19/0000Z 25.0N 61.0W 115 KTS NNNN