000 WTNT44 KNHC 012042 TCDAT4 TROPICAL STORM GASTON DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092010 500 PM AST WED SEP 01 2010 THUNDERSTORMS HAVE CONSOLIDATED NEAR THE CENTER OF THE CYCLONE THIS AFTERNOON...WITH AN INTENSE CONVECTIVE BAND IN THE WESTERN SEMICIRCLE. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 45 KT AND 30 KT...RESPECTIVELY...WITH AMSU ESTIMATES FROM CIRA AND CSU INDICATING 50 KT AND 37 KT. OVERALL THIS SYSTEM APPEARS BETTER ORGANIZED THAN SIX HOURS AGO...AND A BLEND OF THESE DATA GIVES AN INITIAL INTENSITY OF 35 KT...MAKING GASTON THE SEVENTH NAMED STORM OF THE ATLANTIC HURRICANE SEASON. THERE IS STILL A SIGNIFICANT AMOUNT OF DRY AIR TO THE WEST AND NORTH OF THE TROPICAL STORM...WHICH MAY HINDER STRENGTHENING. HOWEVER... ALL OF THE GLOBAL MODELS SHOW THAT A RELATIVELY LIGHT SHEAR ENVIRONMENT WILL BE PRESENT NEAR GASTON FOR THE NEXT SEVERAL DAYS. THE GUIDANCE NOW INDICATES CONSIDERABLY MORE INTENSIFICATION OF GASTON...WITH THE NORMALLY CONSERVATIVE LGEM SHOWING THIS SYSTEM BECOMING A MAJOR HURRICANE BY THE END OF THE PERIOD. THE NHC FORECAST IS RAISED FROM THE PREVIOUS ONE...BUT REMAINS LOWER THAN THE MODEL CONSENSUS. AN AMSR-E PASS AT 1613 UTC HELPED WITH THE INITIAL POSITION AND MOTION...WHICH IS A BIT SLOWER THAN BEFORE AT 280/13. A SUBTROPICAL RIDGE TO THE NORTH OF GASTON IS FORECAST TO WEAKEN SOON AS A MID-LATITUDE TROUGH PASSES BY...WHICH WOULD CAUSE THE STORM TO SLOW DOWN. THIS RIDGE SHOULD REBUILD IN A FEW DAYS AND STEER THE TROPICAL STORM AT AN INCREASINGLY FASTER RATE TO THE WEST OR WEST- NORTHWEST. GLOBAL MODELS HAVE COME INTO SOMEWHAT BETTER AGREEMENT NOW THAT MOST OF THEM ARE INITIALIZING THE STORM...BUT THERE ARE STILL SOME SIGNIFICANT SPEED DIFFERENCES. THE NHC FORECAST IS FASTER THAN ALL OF THE GUIDANCE IN THE SHORT TERM AS IT SEEMS LIKE THE MODELS ARE GENERALLY SHOWING TOO MUCH INTERACTION BETWEEN THE ITCZ AND GASTON. THE NEW FORECAST DOES END UP CLOSE TO THE PREVIOUS ONE BY DAY 5...AND IS NEAR A BLEND OF THE GFS/UKMET/HWRF/GFDL MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 01/2100Z 12.9N 37.0W 35 KT 12HR VT 02/0600Z 13.1N 38.3W 40 KT 24HR VT 02/1800Z 13.4N 39.9W 40 KT 36HR VT 03/0600Z 13.7N 41.2W 45 KT 48HR VT 03/1800Z 14.0N 42.5W 50 KT 72HR VT 04/1800Z 15.0N 45.5W 55 KT 96HR VT 05/1800Z 15.5N 50.0W 65 KT 120HR VT 06/1800Z 16.5N 54.5W 75 KT $$ FORECASTER BLAKE