ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NATE DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152011 1000 AM CDT FRI SEP 09 2011 EARLY MORNING VISIBLE IMAGERY SHOWS THAT NATE HAS A WELL-ORGANIZED CLOUD PATTERN...HOWEVER DRY AIR OVER THE WESTERN SEMICIRCLE CONTINUES TO SUPPRESS DEEP CONVECTION IN THAT PORTION OF THE CIRCULATION AND THE INFRARED PRESENTATION REMAINS UNIMPRESSIVE. THE INITIAL INTENSITY IS HELD AT 55 KT BASED ON A DVORAK CI-NUMBER OF 3.5 FROM TAFB AT 12Z. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL BE INVESTIGATING NATE LATER TODAY TO PROVIDE INFORMATION ON THE STRUCTURE AND INTENSITY OF THE CYCLONE. THE ENVIRONMENT IN TERMS OF SSTS AND UPPER-LEVEL WINDS APPEARS FAVORABLE FOR INTENSIFICATION. HOWEVER...ACCORDING THE SHIPS MODEL OUTPUT...MID-LEVEL DRY AIR WILL REMAIN A LIMITING FACTOR. OVERALL THE INTENSITY GUIDANCE HAS TRENDED A LITTLE LOWER THIS CYCLE...AND THE OFFICIAL FORECAST HAS BEEN NUDGED DOWNWARD A BIT...BUT STILL SHOWS NATE REACHING HURRICANE STRENGTH IN 24 HOURS. NOTE THAT SOME ADDITIONAL STRENGTHENING IS POSSIBLE BETWEEN THE 48-HOUR FORECAST POINT AND LANDFALL...WHICH SHOULD OCCUR BY 72 HOURS. THE NHC FORECAST IS CLOSE TO OR A BIT ABOVE THE LGEM MODEL THROUGH THE PERIOD. BASED ON SATELLITE IMAGERY...NATE FINALLY APPEARS TO BE MOVING SLOWLY NORTHWEST AT AROUND 3 KT AS THE RIDGE TO THE NORTH HAS WEAKENED A LITTLE BIT. HOWEVER...THE MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE RIDGE RESTRENGTHENING NORTH OF NATE IN THE NEXT DAY OR SO. BY 36 HOURS A TURN TOWARD THE WEST IS EXPECTED...WITH A MOTION SOUTH OF DUE WEST POSSIBLE BEFORE LANDFALL. AFTER LANDFALL...THE CYCLONE SHOULD WEAKEN QUICKLY AND DISSIPATE BEFORE 96 HOURS. HOWEVER A 96-HOUR POINT WAS INCLUDED TO SHOW THE SYSTEM WEAKENING BELOW TROPICAL STORM INTENSITY BEFORE DISSIPATION. THE NHC TRACK FORECAST IS AN UPDATE OF THE PREVIOUS ONE AND LIES ROUGHLY BETWEEN THE GFS AND ECMWF IN TERMS OF HEADING AND FORWARD SPEED. GIVEN THE FORECAST TIMING OF THE APPROACH OF TROPICAL STORM CONDITIONS TO THE COAST...A HURRICANE WATCH IS REQUIRED FOR A PORTION OF THE WESTERN GULF COAST OF MEXICO AT THIS TIME. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 20.3N 92.6W 55 KT 65 MPH 12H 10/0000Z 20.6N 93.0W 60 KT 70 MPH 24H 10/1200Z 20.8N 93.8W 65 KT 75 MPH 36H 11/0000Z 20.9N 94.8W 70 KT 80 MPH 48H 11/1200Z 20.8N 95.9W 80 KT 90 MPH 72H 12/1200Z 20.5N 98.5W 50 KT 60 MPH...INLAND 96H 13/1200Z 20.0N 101.0W 25 KT 30 MPH...INLAND 120H 14/1200Z...DISSIPATED $$ FORECASTER BRENNAN NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:02 UTC