Tropical Storm GABRIELLE

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TROPICAL STORM GABRIELLE DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072013
500 PM AST TUE SEP 10 2013
 
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING
GABRIELLE FOUND PEAK SFMR WINDS OF 45-50 KT NORTHWEST AND SOUTHEAST
OF THE CENTER ON THEIR FIRST PASS THROUGH THE STORM...AND THE
INITIAL INTENSITY IS INCREASED TO 50 KT FOR THIS ADVISORY. THE
CENTRAL PRESSURE OF 1004 MB IS BASED ON A DROPSONDE FROM THE
AIRCRAFT. GABRIELLE HAS BEEN ABLE TO STRENGTHEN TODAY DESPITE THE
PRESENCE OF MODERATE SOUTHWESTERLY SHEAR WHICH HAS EXPOSED THE
LOW-LEVEL CENTER TO THE SOUTHWEST OF THE DEEP CONVECTION. WHILE
MODERATE SHEAR IS EXPECTED TO CONTINUE OR EVEN INCREASE OVER THE
NEXT COUPLE OF DAYS...THE STATISTICAL/DYNAMICAL AND GLOBAL MODELS
SHOW SOME STRENGTHENING DURING THAT TIME. THIS SEEMS TO BE SUPPORTED
BY MARGINAL SSTS AND AN INCREASE IN UPPER-LEVEL DIVERGENCE AHEAD OF
A MID/UPPER-LEVEL TROUGH. THE NHC FORECAST SHOWS THE POTENTIAL FOR
SOME STRENGTHENING AND THEN LITTLE CHANGE THROUGH EXTRATROPICAL
TRANSITION IN ABOUT 96 HOURS.
 
THE INITIAL MOTION ESTIMATE IS 360/09. THE MODEL GUIDANCE SHOWS A
TURN TOWARD THE NORTH-NORTHWEST WITH A DECREASE IN FORWARD SPEED
OVER THE NEXT 12 TO 24 HOURS...AS GABRIELLE IS TUGGED WESTWARD BY A
WEAKENING MID/UPPER-LEVEL LOW CURRENTLY SITUATED EAST OF FLORIDA.
AT 48 HOURS AND BEYOND...AN ACCELERATION TOWARD THE NORTHEAST IS
EXPECTED AHEAD OF A DEEP-LAYER TROUGH MOVING THROUGH EASTERN NORTH
AMERICA. THE TRACK MODELS REMAIN IN REASONABLE AGREEMENT ON THE
OVERALL SCENARIO...HOWEVER MUCH OF THE GUIDANCE HAS SHIFTED A
LITTLE TO THE LEFT THIS CYCLE. OVERALL...THE NHC TRACK FORECAST IS
SIMILAR TO THE PREVIOUS ONE THROUGH 48 HOURS AND AFTERWARD HAS BEEN
ADJUSTED A BIT TO THE LEFT...BUT STILL LIES EAST OF THE MULTI-MODEL
CONSENSUS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  10/2100Z 31.5N  64.9W   50 KT  60 MPH
 12H  11/0600Z 32.6N  65.0W   55 KT  65 MPH
 24H  11/1800Z 33.5N  65.5W   55 KT  65 MPH
 36H  12/0600Z 34.3N  66.0W   55 KT  65 MPH
 48H  12/1800Z 35.7N  66.5W   55 KT  65 MPH
 72H  13/1800Z 42.0N  63.5W   55 KT  65 MPH
 96H  14/1800Z 52.0N  52.4W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  15/1800Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 
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