000 WTNT43 KNHC 011452 TCDAT3 TROPICAL STORM HANNA DISCUSSION NUMBER 18 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1100 AM EDT MON SEP 01 2008 HANNA'S OVERALL SATELLITE PRESENTATION HAS BEEN IMPROVING THIS MORNING WITH AN IMPRESSIVE CDO FEATURE NOW COVERING THE LOW-LEVEL CIRCULATION. DVORAK SATELLITE INTENSITY ESTIMATES HAVE INCREASED AND SUGGEST MAX WINDS NEAR 55 KT. I'M GOING TO CONSERVATIVELY SET THE INITIAL INTENSITY TO 50 KT SINCE AN AIR FORCE RECONNAISSANCE AIRCRAFT IS ON ITS WAY. HAVING SAID THAT...A RECENT QUIKSCAT PASS SUGGEST THAT THE LOW-LEVEL CIRCULATION COULD BE LOCATED A LITTLE FARTHER INTO THE DEEP CONVECTION. THIS SUGGEST THAT HANNA COULD BE STRONGER THAN ESTIMATED. THE INTENSITY FORECAST REMAINS TRICKY. WATER VAPOR IMAGERY SUGGESTS THAT THE UPPER-LEVEL LOW WHICH HAD PREVIOUSLY INHIBITED DEVELOPMENT HAS DISSIPATED...AND HANNA NOW FINDS ITSELF IN A VERY SMALL AREA OF LOW SHEAR. HOWEVER...WATER VAPOR IMAGERY ALSO SHOWS STRONG NORTHERLY FLOW ASSOCIATED WITH GUSTAV'S UPPER-LEVEL OUTFLOW JUST NORTH OF HANNA...AND GLOBAL MODELS FORECAST MODERATE TO STRONG NORTHERLY SHEAR PERSISTING DURING THE NEXT DAY OR SO. GIVEN THE UNCERTAINTY...THE OFFICIAL INTENSITY FORECAST IS CLOSE TO THE MODEL CONSENSUS AND SHOWS HANNA BECOMING A HURRICANE A LITTLE SOONER THAN THE PREVIOUS ADVISORY. BY 72 HOURS...GLOBAL MODELS SUGGEST THE SHEAR COULD WEAKEN...AND HANNA COULD FIND ITSELF IN A MORE FAVORABLE ENVIRONMENT FOR STRENGTHENING. STILL...PREDICTING THE ATMOSPHERIC ENVIRONMENT... AND TROPICAL CYCLONE INTENSITY...AT DAYS 3-5 IS VERY DIFFICULT. WHILE THE CENTER IS DIFFICULT TO LOCATE...HANNA APPEARS TO BE MOVING MORE TOWARD THE WEST-SOUTHWEST OR 250/4. A VERY SLOW WEST- SOUTHWEST OR SOUTHWEST MOTION IS EXPECTED DURING THE NEXT 36 HOURS. IN 2 TO 3 DAYS...THE SUBTROPICAL RIDGE IS EXPECTED TO BUILD WESTWARD OVER THE CENTRAL ATLANTIC CAUSING HANNA TO MOVE NORTHWESTWARD WITH AN INCREASE IN FORWARD SPEED. THE NEW OFFICIAL TRACK FORECAST IS ADJUSTED A LITTLE TO THE SOUTH THROUGH 36 HOURS BASED ON THE LATEST MOTION. TRACK GUIDANCE HAS NOT CHANGED SIGNIFICANTLY AT THE EXTENDED RANGES AND NEITHER HAS THE OFFICIAL FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 01/1500Z 23.0N 72.9W 50 KT 12HR VT 02/0000Z 22.8N 73.3W 55 KT 24HR VT 02/1200Z 22.7N 73.7W 55 KT 36HR VT 03/0000Z 22.9N 74.1W 60 KT 48HR VT 03/1200Z 23.7N 74.9W 65 KT 72HR VT 04/1200Z 26.5N 77.5W 70 KT 96HR VT 05/1200Z 30.5N 80.5W 70 KT 120HR VT 06/1200Z 36.5N 82.0W 35 KT...INLAND $$ FORECASTER RHOME/AVILA