WTNT42 KNHC 240835 RRA

TCDAT2



TROPICAL STORM GASTON DISCUSSION NUMBER   7

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016

500 AM AST WED AUG 24 2016



A 0414 UTC AMSR2 MICROWAVE IMAGE REVEALED THAT GASTON'S STRUCTURE

HAS IMPROVED WITH THE DEVELOPMENT OF A WELL-DEFINED LOW-LEVEL CLOUD

RING AND A MID-LEVEL MICROWAVE EYE.  HOWEVER, THE MID-LEVEL CENTER

IS DISPLACED ABOUT 25 N MI TO THE NORTHEAST OF THE LOW-LEVEL

CENTER.  DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB ARE BOTH

T4.0/65 KT, BUT OBJECTIVE NUMBERS ARE STILL BETWEEN 55-60 KT.  GIVEN

THE TILTED STRUCTURE OF THE CYCLONE, THE INITIAL INTENSITY IS ONLY

RAISED TO 60 KT ON THIS ADVISORY.



UNIVERSITY OF WISCONSIN CIMSS SHEAR ANALYSES INDICATE THAT 10 KT

OF SOUTHWESTERLY SHEAR IS AFFECTING GASTON, WHICH COULD EXPLAIN

THE CYCLONE'S TILTED STRUCTURE.  THE SHEAR IS EXPECTED TO REMAIN LOW

ENOUGH DURING THE NEXT 24 HOURS TO ALLOW GASTON TO STRENGTHEN TO A

HURRICANE LATER TODAY.  HOWEVER, THE INTENSIFICATION TREND SHOULD BE

INTERRUPTED AFTER 24 HOURS, CONTINUING THROUGH DAY 3, WHEN GASTON

MOVES INTO A HIGHER SHEAR ZONE TO THE EAST OF A MID-/UPPER-LEVEL

LOW.  SOME STRENGTHENING IS THEN PROBABLE ON DAYS 4 AND 5 WHEN

GASTON MOVES NORTH OF THE UPPER LOW INTO A LOWER-SHEAR ENVIRONMENT.

THE INTENSITY MODELS ARE IN VERY GOOD AGREEMENT ON THIS GENERAL

SCENARIO, AND THE OFFICIAL NHC FORECAST WAS ONLY LOWERED A BIT AT

36 AND 48 HOURS TO BE MORE IN LINE WITH THE IVCN CONSENSUS.



TRACKING THE LOW-LEVEL CENTER OBSERVED IN MICROWAVE DATA YIELDS A

MOTION OF 290/15 KT.  GASTON IS APPROACHING A BREAK IN THE

SUBTROPICAL RIDGE CAUSED BY THE AFOREMENTIONED MID-/UPPER-LEVEL

LOW, AND THE STEERING CURRENTS SHOULD CAUSE THE MOTION TO BECOME=