000 WTNT42 KNHC 281500 TCDAT2 TROPICAL STORM GUSTAV DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008 1100 AM EDT THU AUG 28 2008 THE LAST AIRCRAFT FIX AT ABOUT 1130 UTC SHOWED THE CIRCULATION CENTER HAD BEEN MOVING VERY LITTLE EARLIER THIS MORNING. MY SENSE FROM VISIBLE IMAGERY SINCE THEN IS THAT GUSTAV HAS STARTED MOVING SLOWLY WESTWARD...PERHAPS 265/4. IT IS NOT CLEAR IF THE CENTER WILL PASS DIRECTLY OVER JAMAICA OR WILL HUG THE SOUTH OR NORTH COAST...BUT WITH A WEAK MID-LEVEL RIDGE OVER FLORIDA...ALL MODELS FORECAST GUSTAV TO CONTINUE GENERALLY WESTWARD FOR THE NEXT DAY OR SO. A WEAKNESS IN THE RIDGE OVER THE EASTERN GULF OF MEXICO SHOULD ALLOW GUSTAV TO GRADUALLY TURN TO THE RIGHT DURING THE FOLLOWING FEW DAYS. THE MODELS ALSO FORECAST A MID-LATITUDE RIDGE TO PROPAGATE EASTWARD ACROSS THE EASTERN U.S. DURING THE 3-5 DAY TIME FRAME...BUT SUFFICIENTLY PROGRESSIVE SUCH THAT IT WOULD NOT BLOCK GUSTAV'S NORTHWARD PROGRESS. THE MODELS ARE IN GENERALLY GOOD AGREEMENT ON A TRACK ACROSS THE NORTHWESTERN CARIBBEAN...NEAR OR OVER THE WESTERN TIP OF CUBA...AND ACROSS THE CENTRAL GULF OF MEXICO. SOME OF THE MODELS HINT THAT THE HIGH TO THE NORTH LATE IN THE FORECAST PERIOD COULD FORCE GUSTAV TO TURN A LITTLE BACK TO THE WEST OVER THE NORTHERN GULF...BUT THESE MODELS ARE CURRENTLY IN THE MINORITY. THE NEW OFFICIAL TRACK FORECAST DOES SHOW A SLOWING OF THE FORWARD MOTION AS GUSTAV APPROACHES THE NORTHERN GULF COAST...AND IS NUDGED JUST A LITTLE TO THE EAST TO BE IN LINE WITH THE CONSENSUS. RELIABLE MODELS REMAIN ON EITHER SIDE OF THE FORECAST TRACK...SO ONE SHOULD NOT FOCUS ON THE EXACT OFFICIAL TRACK. THE ADVISORY INTENSITY IS KEPT AT 60 KT BASED ON THE EARLIER AIRCRAFT DATA...AND ANOTHER AIR FORCE PLANE WILL ARRIVE ON THE SCENE THIS AFTERNOON. VISIBLE IMAGERY SUGGESTS THE CYCLONE CONTINUES TO REORGANIZE...BUT THE INTERACTION WITH JAMAICA DURING THE NEXT DAY OR SO MIGHT LIMIT INTENSIFICATION...ALTHOUGH ONLY A SLIGHT INCREASE IN STRENGTH COULD MAKE GUSTAV A HURRICANE AT ANY TIME TODAY. AFTER PASSING JAMAICA...GUSTAV WILL ENCOUNTER THE VERY WARM WATERS OF THE NORTHWESTERN CARIBBEAN WITH ANTICYCLONIC FLOW ALOFT...FAVORING INTENSIFICATION. ANY INTERACTION WITH THE NARROW LANDMASS OF WESTERN CUBA SHOULD NOT HAVE MUCH INFLUENCE ON THE STRENGTH OF GUSTAV OVER THE GULF OF MEXICO...WHERE WATERS WILL BE WARM BUT WIND SHEAR COULD SLOWLY INCREASE. THE NEW OFFICIAL INTENSITY FORECAST CALLS FOR A LITTLE FASTER STRENGTHENING OVER THE NORTHWESTERN CARIBBEAN...BUT IS SIMILAR TO THE PREVIOUS ADVISORY AND THE INTENSITY CONSENSUS THEREAFTER. FORECAST POSITIONS AND MAX WINDS INITIAL 28/1500Z 17.9N 76.1W 60 KT 12HR VT 29/0000Z 17.9N 77.1W 65 KT...NEAR JAMAICA 24HR VT 29/1200Z 18.4N 79.0W 70 KT 36HR VT 30/0000Z 19.1N 80.8W 80 KT 48HR VT 30/1200Z 20.2N 82.6W 95 KT 72HR VT 31/1200Z 23.5N 86.0W 100 KT 96HR VT 01/1200Z 27.0N 89.0W 100 KT 120HR VT 02/1200Z 29.5N 91.0W 100 KT...NEAR COAST OF LA $$ FORECASTER KNABB