000 WTPZ45 KNHC 311442 TCDEP5 TROPICAL STORM GIL DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP102007 800 AM PDT FRI AUG 31 2007 ANIMATED INFRARED IMAGERY INDICATES THAT GIL IS EXHIBITING A STRONG DIURNAL CYCLE IN CONVECTIVE ACTIVITY. AFTER DEEP CONVECTION NEARLY DISAPPEARED BETWEEN 0600 AND 1200 UTC...MOST RECENT IMAGERY SHOWS ANOTHER BURST OF THUNDERSTORMS DEVELOPING NEAR THE CENTER. A TRMM MICROWAVE PASS AT 1117Z INDICATES THE LOW LEVEL CENTER OF GIL STILL REMAINS DISPLACED EAST OF THE CONVECTION...A RESULT OF PERSISTENT UPPER LEVEL EASTERLY SHEAR. SATELLITE INTENSITY ESTIMATES AT 12Z REMAIN AT 35 KT...SO THERE IS NO CHANGE TO THE INITIAL INTENSITY. A QUIKSCAT PASS AT 31/0154Z SHOWED A SMALL AREA OF TROPICAL STORM FORCE WINDS AROUND THE CENTER...AND WAS USED TO FORMULATE THE WIND RADII ESTIMATES. THE ENVIRONMENTAL FACTORS AFFECTING THE INTENSITY OF GIL ARE NOT EXPECTED TO CHANGE MUCH OVER THE NEXT 24 TO 48 HOURS. VERTICAL WIND SHEAR IS FORECAST TO RELAX A BIT...BUT SHOULD STILL PREVENT PERSISTENT DEEP CONVECTION TO REMAIN OVER THE CENTER FOR ANY SIGNIFICANT LENGTH OF TIME. THE FORECAST TRACK NEARLY PARALLELS THE 27C SST ISOTHERM...SO OCEAN TEMPERATURES WILL REMAIN A NEUTRAL INFLUENCE FOR SEVERAL DAYS. GIL IS ENTRAINING STABLE STRATOCUMULUS AIR FROM ITS NORTHWEST SEMICIRCLE INTO ITS CORE...WHICH IN TURN WILL PROBABLY KEEP A LID ON ANY FUTURE DEVELOPMENT. ALL INDICATIONS ARE THAT GIL WILL MAINTAIN ITS CURRENT INTENSITY OR WEAKEN SLIGHTLY OVER THE NEXT 3 DAYS. THE OFFICIAL INTENSITY FORECAST IS SLIGHTLY LOWER THAN SHIPS AND IS CONSISTENT WITH THE PREVIOUS ADVISORY. THE INITIAL MOTION OF 270/9 IS VIRTUALLY UNCHANGED FROM THE PREVIOUS ADVISORY...AS IS THE TRACK FORECAST PHILOSOPHY. TRACK GUIDANCE IS IN VERY GOOD AGREEMENT...AND CONFIDENCE IN THE FORECAST POSITIONS IS FAIRLY HIGH. GIL WILL CONTINUE ALONG A WESTWARD TRACK FOR THE NEXT 24 HOURS FOLLOWED BY A SLIGHT TURN TO THE WEST-NORTHWEST AS IT NEARS THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE TO ITS NORTHEAST. THE GFS MODEL IS SHOWING A WEAKNESS IN THE SUBTROPICAL RIDGE BETWEEN 130W AND 140W IN THE 72-96 HOUR TIME FRAME...BUT NONE OF THE FORECAST AIDS ARE HINTING AT A RECURVATURE TRACK. ONCE GIL WEAKENS TO A REMNANT LOW OVER COOLER WATERS...IT WILL BE STEERED BACK TOWARD THE WEST IN RESPONSE TO THE LOW-LEVEL EASTERLY FLOW AND PROBABLY NOT FEEL THE WEAKNESS IN THE RIDGE AT LONG-RANGE. FORECAST POSITIONS AND MAX WINDS INITIAL 31/1500Z 19.1N 117.4W 35 KT 12HR VT 01/0000Z 19.2N 119.1W 35 KT 24HR VT 01/1200Z 19.4N 121.3W 35 KT 36HR VT 02/0000Z 19.9N 123.6W 35 KT 48HR VT 02/1200Z 20.4N 125.8W 35 KT 72HR VT 03/1200Z 20.7N 130.3W 30 KT 96HR VT 04/1200Z 21.0N 134.5W 25 KT...REMNANT LOW 120HR VT 05/1200Z 21.0N 138.5W 25 KT...REMNANT LOW $$ FORECASTER MUNDELL/BLAKE