000 WTNT42 KNHC 302059 TCDAT2 HURRICANE GUSTAV DISCUSSION NUMBER 25 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008 500 PM EDT SAT AUG 30 2008 THE CENTER OF THE EYE OF GUSTAV HAD BEEN HUGGING THE EASTERN COAST OF THE ISLE OF YOUTH EARLIER THIS AFTERNOON...BUT IS NOW OVER WATER IN BETWEEN THAT ISLAND AND MAINLAND WESTERN CUBA. AIRCRAFT FIXES CONTINUE TO COME IN JUST ABOUT RIGHT ALONG THE PREVIOUS FORECAST TRACK. VISIBLE SATELLITE IMAGERY SUGGESTS GUSTAV HAS BEEN WOBBLING SLIGHTLY...BUT THE INITIAL MOTION APPEARS RELATIVELY WELL-ESTABLISHED AT 315/13...WITH STEERING PROVIDED BY A MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC. THE VARIOUS MODELS HAVE COME INTO BETTER AGREEMENT ON A TRACK INTO THE NORTH-CENTRAL GULF COAST WITHIN THE NEXT COUPLE OF DAYS. THE HWRF...UKMET...AND NOGAPS...WHICH HAD PREVIOUSLY FORECAST A STALL JUST OFFSHORE...HAVE COME INTO THE FOLD WITH THE GFS...GFDL...AND ECMWF...RESULTING IN A CONSENSUS TRACK THAT FALLS VERY CLOSE TO THE PATH OF THE PREVIOUS ADVISORY. THIS AGREEMENT HAS ALSO RESULTED...HOWEVER...IN A CONSENSUS TRACK THAT REACHES THE COAST A LITTLE FASTER. THE NEW OFFICIAL TRACK IS ALMOST EXACTLY ALONG THE PATH OF THE PREVIOUS ADVISORY...BUT MAINTAINS THE CURRENT HEADING AND SPEED ALL THE WAY TO THE COAST...ARRIVING THERE A LITTLE SOONER THAN BEFORE. WHILE THERE IS INCREASED CONFIDENCE IN BOTH THE PATH AND SPEED OF THE TRACK THROUGH ABOUT 48 HOURS...THE MODEL SPREAD IS STILL SUFFICIENTLY LARGE TO SERVE AS A REMINDER THAT WE CANNOT SPECIFY EXACTLY WHERE OR WHEN THE CENTER OF GUSTAV WILL MAKE FINAL LANDFALL. AFTER LANDFALL...ALL OF THE MODELS RESPOND TO WEAKENING STEERING CURRENTS...WELL TO THE SOUTHWEST OF THE HIGH OVER THE NORTHEASTERN UNITED STATES...BY FORECASTING A DRAMATIC SLOWING OF THE FORWARD SPEED OVER LOUISIANA AND EASTERN TEXAS...AND THE OFFICIAL FORECAST AGAIN FOLLOWS SUIT. THE RECON CENTRAL PRESSURES HAVE CONTINUED TO STEADILY FALL...WITH THE MOST RECENT VALUE BEING 942 MB. A FLIGHT-LEVEL WIND OF 143 KT AT 700 MB WAS JUST REPORTED IN THE NORTHEASTERN EYEWALL...WHICH SUPPORTS INCREASING THE ADVISORY INTENSITY TO 130 KT. MODEST ADDITIONAL STRENGTHENING DURING THE NEXT FEW HOURS COULD LEAD TO CATEGORY FIVE INTENSITY AS GUSTAV CROSSES WESTERN CUBA...BUT THE OFFICIAL FORECAST DOES NOT EXPLICITLY CALL FOR CATEGORY FIVE STATUS UNTIL 24 HOURS. AFTER DEPARTING CUBA...THE HURRICANE WILL PASS OVER THE WARM LOOP CURRENT IN THE SOUTHEASTERN GULF OF MEXICO...AND VERTICAL WIND SHEAR IS NOT FORECAST BY THE MODELS TO BECOME PROHIBITIVELY STRONG DURING THE NEXT COUPLE OF DAYS...SO THE OFFICIAL FORECAST MAINTAINS A MAJOR HURRICANE ALL THE WAY TO FINAL LANDFALL. THIS FORECAST IS VERY CLOSE TO THE SHIPS MODEL AND ALSO NOT TOO DIFFERENT FROM THE GFDL AND HWRF. THE NHC WIND SPEED PROBABILITIES...INCLUDED IN THIS ADVISORY PACKAGE IN BOTH TEXT AND GRAPHICAL FORMATS...DEPICT A RELATIVELY SIMILAR RISK OF HURRICANE-FORCE WINDS AT INDIVIDUAL LOCATIONS ALONG A WIDE STRETCH OF THE NORTHERN GULF COAST. GIVEN THAT THESE VALUES ARE SUFFICIENTLY HIGH...AND CONSIDERING THE SLIGHTLY FASTER TRACK TOWARD THE COAST...IT IS TIME TO ISSUE HURRICANE AND TROPICAL STORM WATCHES ALONG THE NORTHERN GULF COAST. FORECAST POSITIONS AND MAX WINDS INITIAL 30/2100Z 22.1N 82.9W 130 KT 12HR VT 31/0600Z 23.4N 84.4W 135 KT 24HR VT 31/1800Z 25.3N 86.5W 140 KT 36HR VT 01/0600Z 27.2N 88.6W 135 KT 48HR VT 01/1800Z 29.0N 90.7W 125 KT 72HR VT 02/1800Z 31.0N 93.0W 70 KT...INLAND 96HR VT 03/1800Z 32.0N 94.5W 35 KT...INLAND 120HR VT 04/1800Z 32.0N 96.0W 30 KT...INLAND $$ FORECASTER KNABB