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| #212224 (Received by flhurricane at: 5:18 AM 01.Sep.2008) TCDAT2 HURRICANE GUSTAV DISCUSSION NUMBER 31 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008 500 AM EDT MON SEP 01 2008 OBSERVATIONS FROM AN AIR FORCE HURRICANE HUNTER AIRCRAFT INDICATE THAT GUSTAV IS NOT STRENGTHENING. THE CENTRAL PRESSURE HAS RISEN SLIGHTLY AND...BASED ON RECENT FLIGHT-LEVEL AND SFMR SURFACE WIND MEASUREMENTS...100 KT IS A GENEROUS ESTIMATE FOR THE CURRENT INTENSITY. WSR-88D RADAR IMAGES SHOW THAT THE EYE WALL IS OPEN OVER THE SOUTHERN SEMICIRCLE...PERHAPS DUE TO THE MID- TO UPPER-LEVEL DRY AIR INTRUSION FROM THE SOUTH THAT WAS DISCUSSED EARLIER. IN FACT...THE AIR FORCE HURRICANE HUNTERS DID NOT REPORT AN EYEWALL. WATER VAPOR IMAGERY ALSO SUGGESTS A DRY INTRUSION AND A RESTRICTION OF THE UPPER-LEVEL OUTFLOW OVER THE SOUTHERN PORTION OF THE HURRICANE. ALSO THE CLOUD PATTERN HAS BECOME A BIT MORE RAGGED ON GEOSTATIONARY SATELLITE PICTURES. BASED ON CURRENT TRENDS AND THE PROXIMITY TO THE COAST...NO SIGNIFICANT INCREASE IN STRENGTH APPEARS LIKELY PRIOR TO LANDFALL. GUSTAV CONTINUES MOVING BRISKLY TOWARD THE NORTHWEST...315/14. THE HURRICANE CONTINUES TO BE STEERED BY THE FLOW TO THE SOUTH AND SOUTHWEST OF A MID-TROPOSPHERIC ANTICYCLONE/HIGH OVER THE EASTERN UNITED STATES. GLOBAL MODELS SHOW THE HIGH WEAKENING OVER THE NEXT DAY OR SO AND THEREFORE GUSTAV'S FORWARD SPEED IS LIKELY TO SLOW LATER TODAY AND TOMORROW...I.E. AFTER THE SYSTEM HAS MOVED INLAND. THE STEERING PATTERN BECOMES ILL-DEFINED LATER IN THE FORECAST PERIOD AND THE TRACK MODELS BECOME HIGHLY DIVERGENT. IF GUSTAV REMAINED A VERTICALLY-COHERENT CYCLONE IT WOULD PROBABLY RESPOND TO AN INCREASING SOUTHWESTERLY UPPER-LEVEL FLOW AS FORECAST BY THE GLOBAL MODELS. HOWEVER IT IS QUITE POSSIBLE THAT THE UPPER-LEVEL PART OF GUSTAV WILL BE SHEARED OFF TO THE NORTHEAST...LEAVING THE LOW-LEVEL CIRCULATION BEHIND IN THE EAST TEXAS AREA. THAT IS BASICALLY WHAT WE ARE INDICATING IN THIS OFFICIAL TRACK FORECAST WHICH SHOWS GUSTAV OR ITS REMNANTS SLOWING TO A CRAWL IN DAYS 3 TO 5. SUCH SLOW MOTION WOULD EXACERBATE THE THREAT OF HEAVY RAINS AND INLAND FLOODING. FORECAST POSITIONS AND MAX WINDS INITIAL 01/0900Z 28.4N 89.5W 100 KT 12HR VT 01/1800Z 29.5N 91.1W 100 KT...INLAND 24HR VT 02/0600Z 30.7N 92.8W 55 KT...INLAND 36HR VT 02/1800Z 31.4N 93.9W 35 KT...INLAND 48HR VT 03/0600Z 31.8N 94.7W 25 KT...INLAND 72HR VT 04/0600Z 32.0N 95.5W 20 KT...INLAND 96HR VT 05/0600Z 32.0N 96.0W 20 KT...INLAND 120HR VT 06/0600Z 32.0N 96.5W 20 KT...REMNANT LOW $$ FORECASTER PASCH |
