000
WTNT44 KNHC 020255
TCDAT4
TROPICAL STORM GASTON DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092010
1100 PM AST WED SEP 01 2010
 
GASTON HAS MAINTAINED A WELL-DEFINED CURVED BAND OF CONVECTION THAT
WRAPS FROM THE WESTERN TO NORTHERN SIDES OF THE CIRCULATION...AND
DVORAK FINAL-T NUMBERS ARE T2.5/35 KT FROM BOTH TAFB AND SAB.  THE
OBJECTIVE ADT ESTIMATE FROM UW-CIMSS IS CURRENTLY T3.3/51 KT...BUT
A RECENT 0013 UTC ASCAT PASS SHOWS WINDS NO HIGHER THAN 25-30 KT.
THE INITIAL INTENSITY IS KEPT AT 35 KT AS A BLEND OF THESE
ESTIMATES.
 
THE OFFICIAL INTENSITY FORECAST HAS AGAIN BEEN INCREASED A BIT FROM
THE PREVIOUS ADVISORY.  ALTHOUGH THERE IS SOME DRY AIR SURROUNDING
THE CYCLONE...GLOBAL MODEL GUIDANCE SUGGESTS THAT THE VERTICAL
SHEAR SHOULD REMAIN LOW...AT LEAST FOR THE NEXT 2-3 DAYS...AND THIS
COULD PREVENT THE DRY AIR FROM HAVING A SIGNIFICANT EFFECT.
STILL...THERE IS A LOT OF UNCERTAINTY IN THE INTENSITY FORECAST
GIVEN THE DIFFERENCES BETWEEN THE DYNAMICAL AND STATISTICAL MODELS.
OVER THE NEXT 5 DAYS...THE GFDL AND HWRF ONLY STRENGTHEN GASTON TO
A STRONG TROPICAL STORM OR MINIMAL HURRICANE...THE SHIPS MODEL
MAKES IT A CATEGORY 2 HURRICANE...AND THE LGEM BRINGS IT TO
CATEGORY 4 INTENSITY.  THE OFFICIAL FORECAST IS A LITTLE ABOVE THE
INTENSITY CONSENSUS FOR THE FIRST 48 HOURS WHEN ENVIRONMENTAL
CONDITIONS SHOULD BE MOST IDEAL AND THEN VERY CLOSE TO THE
CONSENSUS THEREAFTER WHEN EASTERLY SHEAR COULD INCREASE A BIT.
 
THE LATEST SATELLITE FIXES INDICATE THAT GASTON HAS BEGUN TO SLOW
DOWN...POSSIBLY DUE TO A MID-LEVEL TROUGH LOCATED TO ITS
NORTHWEST.  IT IS ALSO A LITTLE FARTHER NORTH THAN PREVIOUSLY
ESTIMATED AND HAS AN INITIAL MOTION OF 280/10 KT.  WITH THE BREAK
IN THE SUBTROPICAL RIDGE...GASTON IS EXPECTED TO CONTINUE TO
SLOW DOWN OVER THE NEXT COUPLE OF DAYS.  THE MULTI-MODEL CONSENSUS
TVCN IS SLOWER THAN THE PREVIOUS FORECAST...SO THE NEW OFFICIAL
FORECAST SHOWS A SLOWER MOTION OVER THE NEXT 36 HOURS...BUT IS
STILL ON THE SAME GENERAL TRACK AS THE PREVIOUS ADVISORY.  BY DAYS
4 AND 5...THE RIDGE IS EXPECTED TO STRENGTHEN...AND THE CYCLONE
SHOULD BEGIN TO MOVE FASTER TO THE WEST.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/0300Z 13.4N  37.7W    35 KT
 12HR VT     02/1200Z 13.5N  38.5W    40 KT
 24HR VT     03/0000Z 13.7N  39.7W    45 KT
 36HR VT     03/1200Z 13.8N  40.8W    50 KT
 48HR VT     04/0000Z 14.0N  42.1W    55 KT
 72HR VT     05/0000Z 14.5N  45.5W    65 KT
 96HR VT     06/0000Z 15.0N  49.5W    75 KT
120HR VT     07/0000Z 16.0N  54.5W    85 KT
 
$$
FORECASTER BERG