Tropical Storm GILMA

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TROPICAL STORM GILMA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP082006
200 PM PDT TUE AUG 01 2006
 
VISIBLE IMAGERY THIS AFTERNOON SHOWS THAT THE LOW-LEVEL CENTER OF
GILMA IS NOW EXPOSED EAST OF THE MAIN CONVECTION DUE TO EASTERLY
VERTICAL WIND SHEAR.  HOWEVER...THE CONVECTION REMAINS QUITE
VIGOROUS WITH CLOUD TOPS TO -80C.  SATELLITE INTENSITY ESTIMATES
FROM ALL AGENCIES ARE 35 KT...SO THAT REMAINS THE INITIAL
INTENSITY.

THE EXPOSED CENTER AND PREVIOUS MICROWAVE IMAGERY SUGGESTS THAT THE
MOTION IS TO THE RIGHT OF THE PREVIOUS ADVISORY...310/7.  WATER
VAPOR IMAGERY AND LARGE-SCALE MODEL ANALYSES INDICATE BROAD
DEEP-LAYER TROUGHING OFF THE WEST COAST OF THE UNITED STATES NORTH
OF 30N...MID/UPPER-LEVEL RIDGING OVER NORTHWESTERN MEXICO AND BAJA
CALIFORNIA...AND A MID/UPPER-LEVEL LOW OR TROUGH OVER CENTRAL
MEXICO.  THE WEST COAST TROUGH IS FORECAST TO AMPLIFY SOUTHWARD BY
72-120 HR.  LARGE-SCALE MODELS GENERALLY RESPOND TO THIS PATTERN
EVOLUTION BY KEEPING ENOUGH RIDGING NORTH OF GILMA TO MOVE IT
WESTWARD THROUGH 120 HR.  ON THE OTHER HAND...THE BAM MODELS...
LBAR...AND THE FSU SUPERENSEMBLE CALL FOR A NORTHWESTWARD TURN
AFTER 72 HR.  THE LARGE-SCALE MODELS INITIALIZED GILMA RATHER
POORLY...EXCEPT THE UKMET WHICH TRACKS THE STORM NORTHWESTWARD
UNTIL DISSIPATION.  ADDITIONALLY...THE OTHER GUIDANCE DOES NOT SEEM
TO REFLECT THE CURRENT MOTION VERY WELL.  SO...THE NEW FORECAST
TRACK IS SHIFTED NORTHWARD FOR THE FIRST 36-48 HR TO REFLECT THE
CURRENT MOTION...AND SHIFTED SOMEWHAT SOUTHWARD AFTER 96 HR TO
REFLECT THE POSSIBILITY THAT THE WEST COAST TROUGH WILL NOT DEEPEN
FAR ENOUGH SOUTHWARD TO STRONGLY TURN GILMA.

LARGE-SCALE MODELS SUGGEST THAT GILMA WILL REMAIN IN EASTERLY SHEAR
THROUGH 36-48 HR...WHICH WILL AT LEAST SLOW INTENSIFICATION.  THE
SHEAR DECREASES SOMEWHAT AFTER THAT TIME...BUT THE SEA SURFACE
TEMPERATURES ALONG THE FORECAST TRACK START DECREASING ABOUT THAT
TIME.  BASED ON THIS...THE INTENSITY FORECAST WILL CALL FOR SLOW
STRENGTHENING UNTIL 48 HR...AND SLOW WEAKENING THEREAFTER.  THE
INTENSITY FORECAST IS STRONGER THAN ALL THE GUIDANCE...SO GILMA
COULD STRENGTHEN LESS THAN CURRENTLY FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/2100Z 14.4N 105.6W    35 KT
 12HR VT     02/0600Z 15.0N 106.5W    35 KT
 24HR VT     02/1800Z 15.3N 107.9W    40 KT
 36HR VT     03/0600Z 15.7N 109.5W    45 KT
 48HR VT     03/1800Z 16.0N 111.2W    50 KT
 72HR VT     04/1800Z 17.0N 114.5W    45 KT
 96HR VT     05/1800Z 18.5N 117.5W    40 KT
120HR VT     06/1800Z 21.0N 119.5W    35 KT
 
$$
FORECASTER BEVEN
 
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