000 WTNT42 KNHC 300301 TCDAT2 HURRICANE GUSTAV DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008 1100 PM EDT FRI AUG 29 2008 REPORTS FROM AIR FORCE RESERVE AND NOAA HURRICANE HUNTER AIRCRAFT SHOW THAT GUSTAV HAS A 25 NM WIDE EYE THAT IS BECOMING BETTER DEFINED IN RECENT SATELLITE IMAGERY. RECENT TRMM AND SSM/I IMAGERY ALONG WITH CUBAN RADAR DATA SUGGESTS THAT AN OUTER EYEWALL WITH A DIAMETER OF ABOUT 100 N MI IS FORMING...AND THE NOAA PLANE REPORTED 88 KT FLIGHT-LEVEL WINDS AT 770 MB IN THE CORRESPONDING OUTER WIND MAXIMUM. RELIABLE-LOOKING DATA FROM THE SFMR SHOWS 65-70 KT SURFACE WINDS IN BOTH THE INNER AND OUTER WIND MAXIMA...BUT THE HURRICANE FORCE WINDS ARE CURRENTLY CONFINED TO THE NORTHEASTERN QUADRANT. THE INITIAL INTENSITY IS SET TO 70 KT IN AGREEMENT WITH THE AIRCRAFT DATA. THE INITIAL MOTION IS 305/9. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PACKAGE...WITH GUSTAV EXPECTED TO MOVE GENERALLY NORTHWESTWARD ON THE SOUTHWEST SIDE OF A LOW/MID-LEVEL RIDGE OVER THE EASTERN UNITED STATES. THERE HAS ALSO BEEN LITTLE CHANGE IN THE GUIDANCE...WITH SOME CONTINUING DISAGREEMENT ON HOW MUCH RIDGING WILL EXTEND WESTWARD TO THE NORTH OF GUSTAV AND HOW GUSTAV WILL INTERACT WITH AN UPPER-LEVEL TROUGH OVER THE GULF OF MEXICO. THE GUIDANCE IS TIGHTLY CLUSTERED THROUGH 48 HR AND THEN SHOWS SOME SPREAD. THE GFDL REMAINS ON THE EASTERN SIDE OF THE GUIDANCE ENVELOPE AND CALLS FOR LANDFALL IN SOUTHEASTERN LOUISIANA...WHILE THE UKMET CALLS FOR A WESTWARD TURN AND LANDFALL ON THE MIDDLE TO UPPER TEXAS COAST. THE REMAINDER OF THE GUIDANCE LIES BETWEEN THESE EXTREMES. THE NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS FORECAST FOR THE FIRST 72 HR...THEN IS SLOWER AND A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST THEREAFTER. IT LIES IN THE EASTERN SIDE OF THE GUIDANCE ENVELOPE. THE INTENSITY FORECAST REMAINS PROBLEMATIC. WHILE GUSTAV HAS GOOD OUTFLOW IN ALL QUADRANTS...WATER VAPOR IMAGERY SUGGESTS WESTERLY FLOW ASSOCIATED WITH THE GULF OF MEXICO TROUGH UNDERCUTTING THE OUTFLOW. THIS...COMBINED WITH THE CONCENTRIC WIND MAXIMA...MAY BE SLOWING INTENSIFICATION. GUSTAV IS OVER WARM WATER WITH HIGH OCEANIC HEAT CONTENT...AND SHOULD REMAIN OVER SUCH WATER UNTIL IS PASSES NORTH OF THE LOOP CURRENT IN 48-60 HR. THUS...THERE IS A DISTINCT POSSIBILITY OF RAPID INTENSIFICATION IF THE STORM STRUCTURE AND THE INTERACTION WITH THE TROUGH PERMIT. THE SHIPS MODEL CALLS FOR A PEAK INTENSITY OF 104 KT...THE LGEM 97 KT...THE HWRF 114 KT...THE FLORIDA STATE SUPERENSEMBLE 114 KT...AND THE GFDL 129 KT. BASED ON THIS AND THE PREMISE THAT THE INTERACTION WITH THE TROUGH WILL ALLOW STEADY STRENGTHENING...THE FORECAST PEAK INTENSITY IS INCREASED TO 115 KT. GUSTAV COULD GET STRONGER THAN THAT IF RAPID INTENSIFICATION OCCURS. THE INTENSITY FORECAST SHOWS A SLIGHT WEAKENING AT 72 HR AS GUSTAV REACHES LOWER OCEANIC HEAT CONTENT AND POSSIBLE ENCOUNTERS SOME WESTERLY SHEAR. HOWEVER... GUSTAV IS EXPECTED TO MAKE LANDFALL AS A MAJOR HURRICANE. THE FINAL FLY IN THE OINTMENT IS THE POSSIBILITY OF EYEWALL REPLACEMENT CYCLES... WHICH COULD SIGNIFICANTLY AFFECT THE INTENSITY. FORECAST POSITIONS AND MAX WINDS INITIAL 30/0300Z 19.5N 80.4W 70 KT 12HR VT 30/1200Z 20.6N 81.8W 85 KT 24HR VT 31/0000Z 22.3N 83.7W 100 KT...INLAND 36HR VT 31/1200Z 24.0N 85.6W 105 KT 48HR VT 01/0000Z 25.7N 87.6W 115 KT 72HR VT 02/0000Z 28.5N 90.5W 110 KT 96HR VT 03/0000Z 30.5N 93.0W 80 KT...INLAND 120HR VT 04/0000Z 31.5N 94.0W 45 KT...INLAND $$ FORECASTER BEVEN