WTNT42 KNHC 272040 RRA

TCDAT2



TROPICAL STORM GASTON DISCUSSION NUMBER  21

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016

500 PM AST SAT AUG 27 2016



THE INNER-CORE CONVECTION OF GASTON HAS CONTINUED TO INCREASE WITH

THE CDO HAVING EXPANDED AND BECOME MORE SYMMETRICAL. SUBJECTIVE

SATELLITE INTENSITY ESTIMATES REMAIN T4.0/65 KT AND T3.5/55 KT FROM

TAFB AND SAB, RESPECTIVELY, AND THE LATEST UW-CIMSS ADT VALUE IS

T3.9/63 KT. AN AVERAGE OF THESE ESTIMATES SUPPORTS MAINTAINING THE

INITIAL INTENSITY AT 60 KT, WHICH COULD BE CONSERVATIVE.



GASTON'S INITIAL MOTION ESTIMATE IS 320/08 KT. THERE IS NO

SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK REASONING. GASTON

IS EXPECTED TO CONTINUE MOVING NORTHWESTWARD AND GRADUALLY

DECELERATE DURING THE NEXT TWO DAYS AS THE CYCLONE MOVES INTO A

BREAK IN THE BERMUDA-AZORES RIDGE. A SHORTWAVE TROUGH AND ASSOCIATED

FRONTAL SYSTEM IS FORECAST TO APPROACH GASTON BY 72 HOURS AND SLOWLY

LIFT OUT THE TROPICAL CYCLONE TO THE NORTH AND NORTHEAST. ON DAYS 4

AND 5, GASTON IS EXPECTED TO GET CAUGHT UP IN THE MID-LATITUDE

WESTERLY FLOW AHEAD OF THE AFOREMENTIONED FRONTAL SYSTEM AND

ACCELERATE EAST-NORTHEASTWARD. THE NEW NHC TRACK MODEL GUIDANCE IS

IN MUCH BETTER AGREEMENT NOW THAT THE ECMWF MODEL HAS MADE A

SIGNIFICANT EASTWARD SHIFT IN ITS TRACK FORECAST AND IS MUCH CLOSER

TO THE PREVIOUS ADVISORY TRACK. THE NEW OFFICIAL FORECAST TRACK WAS

ONLY SHIFTED EASTWARD SLIGHTLY TO COME MORE IN LINE WITH THE

CONSENSUS MODELS TVCN AND GFEX. HOWEVER, THE TRACK SHIFT ALSO

RESULTED IN A SIGNIFICANT DECREASE IN THE FORWARD SPEED ON DAYS 3,

4, AND 5.



THE GLOBAL AND REGIONAL MODELS CONTINUE TO INDICATE THAT GASTON=