HURRICANE GUSTAV DISCUSSION NUMBER 6 - HURRICANE GUSTAV DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008 1100 AM EDT TUE AUG 26 2008 AN AIR FORCE RECONNAISSANCE MISSION EARLY THIS MORNING FOUND PEAK FLIGHT-LEVEL WINDS OF 91 KT...AND

HURRICANE GUSTAV DISCUSSION NUMBER 6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008
1100 AM EDT TUE AUG 26 2008

AN AIR FORCE RECONNAISSANCE MISSION EARLY THIS MORNING FOUND PEAK FLIGHT-LEVEL WINDS OF 91 KT...AND AN SFMR SURFACE WIND OF 78 KT. THESE MEASUREMENTS SUPPORT AN INITIAL INTENSITY OF 80 KT. A DROPSONDE RELEASED IN THE EYE OF GUSTAV DURING THE LAST AIRCRAFT PASS THROUGH THE CENTER JUST BEFORE 1200 UTC...FOUND A SURFACE PRESSURE OF 982 MB...BUT WITH 12 KT OF WIND AT THE SURFACE...SO THE MINIMUM PRESSURE HAS BEEN ESTIMATED SLIGHTLY LOWER. THE AIRCRAFT AND EARLIER MICROWAVE SATELLITE IMAGERY INDICATE THE PRESENCE OF A VERY SMALL EYE...HOWEVER THE EYE HAS NOT YET BECOME APPARENT IN CONVENTIONAL SATELLITE IMAGERY. GUSTAV CONTINUES TO MOVE NORTHWESTWARD TOWARD THE SOUTHERN COAST OF HAITI...WITH AN INITIAL MOTION ESTIMATE OF 325/8. TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT ON A TURN TOWARD THE WEST-NORTHWEST VERY SOON AROUND THE SOUTH SIDE OF A MID- TO UPPER-LEVEL RIDGE LOCATED OVER FLORIDA. THERE REMAINS A LARGE AMOUNT OF SPREAD IN THE MODELS AT 72 HOURS AND BEYOND. THE 00Z UKMET AND ECMWF MODELS MAINTAIN THE RIDGE OVER THE GULF OF MEXICO...WHICH KEEPS GUSTAVE MOVING WESTWARD TOWARDS THE YUCATAN PENINSULA. THE GFDL...HWRF...AND GFS WEAKEN THE RIDGE WHICH ALLOWS FOR A WEST-NORTHWESTWARD MOTION INTO THE CENTRAL GULF OF MEXICO. THE NEW NHC TRACK FORECAST LEANS TOWARD THE GFS/HWRF SCENARIO AND IS A LITTLE TO THE RIGHT OF THE MODEL CONSENSUS. CONDITIONS APPEAR FAVORABLE FOR ADDITIONAL STRENGTHENING BEFORE THE CENTER REACHES MOUNTAINOUS TERRAIN ALONG THE SOUTHERN COAST OF HAITI. SOME WEAKENING IS FORECAST DURING GUSTAV'S PASSAGE OVER LAND...AND SINCE IT IS A VERY SMALL SYSTEM IT COULD WEAKEN A LITTLE MORE THAN SHOWN BELOW. THEREAFTER...GUSTAV IS EXPECTED TO BE OVER WARM WATERS AND IN A LOW SHEAR ENVIRONMENT...WHICH FAVORS STRENGTHENING. THE OFFICIAL FORECAST IS BELOW THAT OF THE GFDL... BUT IS CLOSE TO THE INTENSITY CONSENSUS AND THE HWRF. ONE SHOULD REMEMBER THAT 4 AND 5 DAY FORECASTS ARE SUBJECT TO POTENTIALLY LARGE ERRORS IN BOTH LOCATION AND INTENSITY. FORECAST POSITIONS AND MAX WINDS INITIAL 26/1500Z 17.9N 72.4W 80 KT 12HR VT 27/0000Z 18.6N 73.3W 75 KT 24HR VT 27/1200Z 19.1N 74.6W 80 KT 36HR VT 28/0000Z 19.3N 75.9W 85 KT 48HR VT 28/1200Z 19.4N 77.3W 90 KT 72HR VT 29/1200Z 19.9N 80.2W 100 KT 96HR VT 30/1200Z 21.5N 83.5W 105 KT 120HR VT 31/1200Z 24.0N 87.0W 105 KT


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