000 WTNT42 KNHC 310308 TCDAT2 HURRICANE GUSTAV DISCUSSION NUMBER 26 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008 1100 PM EDT SAT AUG 30 2008 THE EYE OF GUSTAV CROSSED WESTERN CUBA DURING THE PAST SEVERAL HOURS AND IS NOW OVER THE SOUTHEASTERN GULF OF MEXICO. THE HURRICANE WEAKENED DURING PASSAGE OVER LAND...WITH THE EYE BECOMING CLOUD FILLED AND THE EYEWALL CONVECTION BECOME LESS IMPRESSIVE IN BOTH SATELLITE AND RADAR DATA. IT IS ESTIMATED THAT THE INITIAL INTENSITY HAS DECREASED TO 120 KT. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL ARRIVE IN THE STORM ABOUT 06Z TO DETERMINE THE ACTUAL INTENSITY. THE MOTION HAS BEEN WOBBLING BETWEEN 315 AND 320 DEGREES AT 13 KT...WITH 320/13 USED IN THIS PACKAGE. THERE IS NO CHANGE IN THE SYNOPTIC REASONING...WITH GUSTAV BEING STEERED NORTHWESTWARD BY A MID-LEVEL RIDGE OVER THE SOUTHEASTERN UNITED STATES...AND THEN BY AN AMPLIFYING MID-LEVEL RIDGE OVER THE EASTERN UNITED STATES. THE TRACK GUIDANCE IS TIGHTLY CLUSTERED THROUGH 72 HR...CALLING FOR GUSTAV TO TRACK ACROSS THE GULF OF MEXICO AND MAKE LANDFALL IN SOUTHEASTERN OR SOUTH CENTRAL LOUISIANA. THE NEW FORECAST TRACK FOLLOWS THIS SCENARIO IS LIES JUST TO THE EAST OF THE PREVIOUS TRACK. AFTER LANDFALL...THE DYNAMICAL MODELS DISAGREE ON HOW MUCH MID-LEVEL RIDGING WILL DEVELOP NORTH AND WEST OF GUSTAV...WITH A CONSIDERABLE SPREAD IN THE GUIDANCE. THE TRACK FORECAST AT THAT TIME CALLS FOR A SLOW WESTWARD MOTION. IT SHOULD BE NOTED THAT THE 12Z UKMET FORECASTS GUSTAV TO TURN SOUTHWESTWARD AS IT REACHES THE LOUISIANA COAST...WHICH APPEARS UNLIKELY AT THIS TIME. THE INTENSITY FORECAST REMAINS PROBLEMATIC. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SUGGEST THAT THE INTENSIFICATION OCCURRED DESPITE ABOUT 20 KT OF SOUTHERLY VERTICAL SHEAR CAUSED BY AN UPPER-LEVEL TROUGH OVER THE GULF OF MEXICO. THE PRESENCE OF THIS SHEAR IS SUPPORTED BY RADAR DATA FROM THE KEY WEST WSR-88D... WHICH CURRENTLY SHOWS A WEAK SOUTHERN EYEWALL AND LITTLE PRECIPITATION SOUTH OF THE EYEWALL. THE SHIPS MODEL SUGGESTS THE SHEAR SHOULD DIMINISH SOME DURING THE NEXT 18 HR...THEN INCREASE AGAIN AS GUSTAV MOVES BETWEEN THE TROUGH AND AN UPPER-LEVEL ANTICYCLONE TO THE SOUTHEAST. ON THE OCEAN SIDE...GUSTAV IS FORECAST TO PASS OVER THE LOOP CURRENT DURING THE NEXT 24 HOURS... THEN POSSIBLY PASS OVER A COUPLE OF COLD EDDIES NORTH OF 26N. ALL GUIDANCE FORECAST RE-INTENSIFICATION DURING THE NEXT 24 HR...SO THE INTENSITY FORECAST WILL CALL FOR A PEAK INTENSITY OF 135 KT IN 24 HR...FOLLOWED BY SLIGHT WEAKENING BEFORE LANDFALL DUE TO SHEAR AND LOWER HEAT CONTENT...THEN FASTER WEAKENING OVER LAND. DUE TO THE VARIOUS FACTORS...THIS IS A LOW CONFIDENCE INTENSITY FORECAST. HURRICANE WARNINGS WILL LIKELY BE REQUIRED FOR PORTIONS FOR THE NORTHERN GULF COAST ON THE NEXT ADVISORY. FORECAST POSITIONS AND MAX WINDS INITIAL 31/0300Z 23.1N 83.8W 120 KT 12HR VT 31/1200Z 24.6N 85.3W 130 KT 24HR VT 01/0000Z 26.5N 87.4W 135 KT 36HR VT 01/1200Z 28.3N 89.5W 130 KT 48HR VT 02/0000Z 29.8N 91.2W 120 KT...INLAND 72HR VT 03/0000Z 31.5N 93.0W 50 KT...INLAND 96HR VT 04/0000Z 32.5N 94.5W 30 KT...INLAND 120HR VT 05/0000Z 32.5N 96.0W 25 KT...INLAND $$ FORECASTER BEVEN