WTNT42 KNHC 270252 RRA

TCDAT2



TROPICAL STORM GASTON DISCUSSION NUMBER  18

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016

1100 PM AST FRI AUG 26 2016



THE STRUCTURE OF GASTON APPEARS TO BE SLOWLY IMPROVING, WITH LESS

EVIDENCE OF VERTICAL SHEAR THAN EARLIER TODAY.  DEEP CONVECTION HAS

BEEN FORMING FAIRLY CLOSE TO THE CENTER IN A MORE SYMMETRIC FASHION,

BUT STILL HASN'T BEEN ABLE TO PERSIST FOR VERY LONG.  SUBJECTIVE

ESTIMATES ARE A LITTLE HIGHER THAN EARLIER, BUT STILL SUPPORT AN

INITIAL WIND SPEED OF 55 KT FOR THIS ADVISORY.



GASTON SHOULD MOVE INTO A LOW-SHEAR, WARM-WATER ENVIRONMENT DURING

THE NEXT 2 OR 3 DAYS, WHICH WOULD USUALLY SUPPORT A GREAT DEAL OF

STRENGTHENING.  HOWEVER, A KEY HINDERING FACTOR REMAINS THE NEARBY

LOW-LEVEL MOISTURE, WHICH IS FORECAST TO SUBSTANTIALLY DECREASE

DURING THE NEXT FEW DAYS.  THIS SHOULD TEMPER THE EXPECTED

INTENSIFICATION AND REDUCE THE CHANCES FOR RAPID STRENGTHENING.

GASTON IS LIKELY TO ENCOUNTER INCREASING UPPER-LEVEL FLOW BEYOND 3

DAYS, WHICH PROBABLY WILL START A WEAKENING TREND IN COMBINATION

WITH GRADUALLY COOLING SSTS.  MODEL GUIDANCE IS GENERALLY IN GOOD

AGREEMENT ON THIS SCENARIO, WITH LESS SPREAD IN THE INTENSITY

MODELS THAN IS TYPICALLY SEEN.  THE NEW PREDICTION IS A BLEND OF

THE PREVIOUS FORECAST AND THE INTENSITY CONSENSUS.



MICROWAVE DATA SUGGEST THAT GASTON CONTINUES TO MOVE NORTHWESTWARD,

NOW AT ABOUT 13 KT, A BIT SLOWER THAN BEFORE.  THE CYCLONE IS

MOVING BETWEEN A STRONG UPPER LOW TO THE SOUTHWEST AND A SUBTROPICAL

RIDGE TO ITS NORTHEAST.  THE RIDGE IS FORECAST TO GRADUALLY WEAKEN,

RESULTING IN GASTON DECELERATING OVER THE NEXT COUPLE OF DAYS.=