000 WTPZ42 KNHC 310255 TCDEP2 TROPICAL STORM GIL DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP072013 800 PM PDT TUE JUL 30 2013 CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY CONTINUES TO SHOW INCREASED ORGANIZATION OF BOTH THE INNER CORE CONVECTION AND OUTER CONVECTIVE BANDING FEATURES. A RECENT AMSU OVERPASS AT 30/2227 UTC INDICATED A LARGE CURVED BAND OF CONVECTION WRAPPING MORE THAN 70 PERCENT AROUND THE CIRCULATION CENTER. THE INITIAL INTENSITY OF 40 KT IS BASED ON A BLEND OF SATELLITE INTENSITY ESTIMATES OF T2.5/35 KT FROM TAFB AND ADT...AND A 2124 UTC AMSU ESTIMATE OF 48 KT. UPPER-LEVEL OUTFLOW IS SYMMETRICAL AND EXPANDING...WITH A WEAK POLEWARD OUTFLOW CHANNEL HAVING BECOME BECOME ESTABLISHED SINCE THE LAST ADVISORY. THE INITIAL MOTION ESTIMATE REAMINS 285/13 BASED ON VISIBLE AND MICROWAVE SATELLITE FIX DATA. A MID-LEVEL RIDGE EXTENDS WESTWARD FROM THE SOUTHWESTERN UNITED STATES ACROSS THE EASTERN NORTH PACIFIC TO THE NORTH OF GIL. THIS VERY STABLE STEERING FLOW PATTERN IS EXPECTED TO KEEP THE CYCLONE MOVING IN A GENERAL WEST-NORTHWESTWARD MOTION FOR THE NEXT 3-4 DAYS...FOLLOWED BY A GRADUAL TURN TOWARD THE WEST THEREAFTER. A GRADUAL DECREASE IN FORWARD SPEED IS FORECAST BY 24-36 HOURS AS GIL APPROACHES A WEAKNESS IN THE SUBTROPICAL RIDGE. THE OFFICIAL FORECAST IS BASICALLY JUST AN UPDATE OF THE THE PREVIOUS ADVISORY TRACK...AND IS CLOSE TO BUT SLIGHTLY SLOWER THAN THE MULTI-MODEL CONSENSUS TVCE. BASED ON THE LAST FEW VISIBLE SATELLITE IMAGES SHOWING A CDO-LIKE FEATURE DEVELOPING...PLUS THE PRONOUNCED BANDING FEATURE NOTED IN THE LATEST AMSU MICROWAVE DATA...GIL APPEARS POISED TO STEADILY INTENSIFY FOR AT LEAST THE NEXT 48 HOURS. GIVEN THE CURRENT OUTFLOW PATTERN THAT IS FORECAST BY THE GFS MODEL TO CONTINUE TO DEVELOP AND EXPAND...THE OFFICIAL INTENSITY FORECAST COULD BE TOO LOW. REGARDLESS...OF THE DEVELOPMENT RATE...ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR AT LEAST MODEST STRENGTHENING TO OCCUR...AND THE CYCLONE IS EXPECTED TO BECOME A HURRICANE BY 48 HOURS. AFTER A SHORT LEVELING OFF PERIOD...GIL IS EXPECTED TO BEGIN A SLOW WEAKENING TREND BY 96 HOURS AS THE CYCLONE MOVES OVER SLIGHTLY COOLER WATER AND INTO A DRIER AND MORE STABLE AIRMASS. THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IS CLOSE TO A BLEND OF THE SHIPS AND LGEM STATISTICAL-DYNAMICAL MODELS. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 13.1N 117.6W 40 KT 45 MPH 12H 31/1200Z 13.6N 119.3W 50 KT 60 MPH 24H 01/0000Z 14.2N 121.5W 55 KT 65 MPH 36H 01/1200Z 14.7N 123.5W 60 KT 70 MPH 48H 02/0000Z 15.2N 125.5W 65 KT 75 MPH 72H 03/0000Z 15.9N 128.8W 65 KT 75 MPH 96H 04/0000Z 16.4N 132.0W 55 KT 65 MPH 120H 05/0000Z 16.5N 135.5W 45 KT 50 MPH $$ FORECASTER STEWART