ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM HURRICANE HERNAN DISCUSSION NUMBER 20 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008 800 AM PDT MON AUG 11 2008 OVER THE PAST SIX HOURS OR SO...DEEP CONVECTION AROUND THE CENTER OF HERNAN HAS CONTRACTED IN AREA AND THE EYE HAS CONTINUED TO FILL WITH CLOUDS. DVORAK DATA T-NUMBERS ARE 4.0 AND 4.5 FROM TAFB AND SAB... RESPECTIVELY...SO THE INITIAL INTENSITY WILL BE MAINTAINED AT 70 KT AS A CONSENSUS OF THESE NUMBERS. HERNAN IS NOW OVER COOL SEA SURFACE TEMPERATURES NEAR 24C BUT THE POWERFUL CIRCULATION HAS CAUSED THE SYSTEM TO BE SOMEWHAT RESISTANT TO A RAPID DECAY. IN ADDITION...THE FORECAST TRACK TAKES HERNAN WEST-SOUTHWEST PARALLEL TO THE STRONG SST GRADIENT SO ONLY GRADUAL WEAKENING IS FORECAST OVER THE NEXT 48 HOURS IN LINE WITH SHIPS AND THE INTENSITY CONSENSUS. THERE IS A POSSIBILITY THAT HERNAN COULD MAINTAIN TROPICAL CYCLONE STATUS THROUGH DAYS 4 AND 5 EVEN THOUGH THE OFFICIAL FORECAST CALLS FOR WEAKENING TO A REMNANT LOW. HERNAN HAS BEEN ON A SHORT-TERM TRACK JUST SLIGHTLY NORTH OF THE PREVIOUS FORECAST WITH AN INITIAL MOTION OF 285/9. HERNAN IS APPROACHING A MIDDLE TO UPPER-LEVEL TROUGH NORTHEAST OF HAWAII AND IS LOCATED NEAR AN AREA OF LOW PRESSURE NEAR 16N143W...BOTH OF WHICH MAY BE CONTRIBUTING TO THE RECENT NORTHWESTWARD MOTION. ONCE THE CYCLONE BEGINS ITS WEAKENING TREND...A SOUTHWESTWARD TURN IS EXPECTED TO COMMENCE AS THE CIRCULATION IS STEERED BY THE LOW-LEVEL RIDGE. HERNAN IS EXPECTED TO CROSS INTO THE CENTRAL PACIFIC BASIN SOMETIME ON THURSDAY. WIND RADII HAVE BEEN CONTRACTED BASED ON AN EXCELLENT 0620 UTC ASCAT PASS COVERING MOST OF HERNAN'S CIRCULATION. FORECAST POSITIONS AND MAX WINDS INITIAL 11/1500Z 19.0N 130.2W 70 KT 12HR VT 12/0000Z 19.0N 131.2W 60 KT 24HR VT 12/1200Z 18.6N 132.7W 50 KT 36HR VT 13/0000Z 18.2N 134.2W 40 KT 48HR VT 13/1200Z 17.7N 135.7W 35 KT 72HR VT 14/1200Z 16.5N 139.0W 30 KT 96HR VT 15/1200Z 15.5N 143.0W 25 KT...REMNANT LOW 120HR VT 16/1200Z 15.5N 147.0W 25 KT...REMNANT LOW $$ FORECASTER BERG/PASCH NNNN
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