WTNT42 KNHC 271440 RRA

TCDAT2



TROPICAL STORM GASTON DISCUSSION NUMBER  20

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016

1100 AM AST SAT AUG 27 2016



A 0954Z WINDSAT MICROWAVE IMAGE INDICATED THAT GASTON HAD DEVELOPED

A 15-NMI-DIAMETER LOW-LEVEL EYE THAT WAS EMBEDDED IN THE CENTER OF

THE NEARLY CIRCULAR CENTRAL DENSE OVERCAST. SUBJECTIVE SATELLITE

INTENSITY ESTIMATES ARE T4.0/65 KT AND T3.5/55 KT FROM TAFB AND

SAB, RESPECTIVELY, AND THE LATEST UW-CIMSS ADT VALUE IS T3.7/59 KT.

AN AVERAGE OF THESE ESTIMATES SUPPORTS INCREASING THE INITIAL

INTENSITY TO 60 KT.



AS ANTICIPATED, GASTON HAS SLOWED DOWN AND THE MOTION ESTIMATE IS

NOW 310/09 KT. THE CYCLONE IS FORECAST TO MAINTAIN A NORTHWESTWARD

MOTION AND CONTINUE TO DECELERATE DURING THE NEXT 48 HOURS AS GASTON

MOVES INTO A BREAK IN THE SUBTROPICAL RIDGE LOCATED TO ITS NORTH. A

MID-LEVEL SHORTWAVE TROUGH IS FORECAST TO DIG SOUTHEASTWARD FROM

CANADA AND THE NORTHEASTERN UNITED STATES BY 72 HOURS, AND FORCE

GASTON TO MAKE A SHARP TURN TOWARD THE NORTH AND NORTHEAST WHEN THE

CYCLONE IS LOCATED SEVERAL HUNDRED MILES EAST OF BERMUDA. ON DAYS 4

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

LATITUDE WESTERLIES AND ACCELERATE EAST-NORTHEASTWARD OVER THE NORTH

ATLANTIC. THE NEW OFFICIAL FORECAST TRACK IS A LITTLE SLOWER THAN

THE PREVIOUS ADVISORY TRACK AND HAS BEEN SHIFTED A LITTLE TO THE

EAST, BUT NOT NEARLY AS FAR EAST AS THE CONSENSUS MODEL TVCN OUT OF

RESPECT FOR THE ECWMF MODEL, WHICH IS CLOSE TO THE PREVIOUS

FORECAST TRACK.



GASTON HAS MAINTAINED TWO PRONOUNCED UPPER-LEVEL OUTFLOW JETS TO ITS

EAST AND SOUTHWEST. THESE JETS ARE FLOWING INTO LARGE UPPER-LEVEL=