Tropical Depression GILMA

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TROPICAL DEPRESSION GILMA DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP082006
200 PM PDT WED AUG 02 2006
 
SATELLITE IMAGERY INDICATES THAT A BURST OF CONVECTION FORMED OVER
THE CENTER OF GILMA DURING THE DAY...WHICH WAS ENOUGH TO BRING THE
SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB UP TO 35 KT AT 18Z. 
SINCE THAT TIME...THE CONVECTION HAS BECOME RATHER DISORGANIZED AS
THE BURST HAS WEAKENED.  BASED ON THIS...THE INITIAL INTENSITY WILL
REMAIN 30 KT...AND GILMA WILL REMAIN A TROPICAL DEPRESSION.

THE INITIAL MOTION IS 290/5.  GILMA IS CURRENTLY EMBEDDED IN AN AREA
OF WEAK STEERING FLOW SOUTHEAST OF A MID/UPPER-LEVEL TROUGH LOCATED
WEST OF THE UNITED STATES WEST COAST AND A MID-LEVEL RIDGE CENTERED
OVER CENTRAL MEXICO.  THE LARGE-SCALE MODELS FORECAST THE TROUGH TO
GRADUALLY WEAKEN WITH THE RIDGE BUILDING WESTWARD INTO THE PACIFIC. 
THIS EVOLUTION SHOULD ALLOW GILMA TO CONTINUE A WEST-NORTHWESTWARD
TO NORTHWESTWARD MOTION WITH POSSIBLY SOME INCREASE IN FORWARD
SPEED.  WHILE THE TRACK GUIDANCE GENERALLY AGREES WITH THIS
SCENARIO...THE GFS CALLS FOR A MORE WESTWARD INITIAL MOTION THAT
LOOKS SUSPECT...WHILE THE UKMET CONTINUES TO FORECAST A
NORTHWESTWARD MOTION.  THE NEW FORECAST TRACK IS SHIFTED A LITTLE
TO THE RIGHT OF THE PREVIOUS TRACK.  IT IS CLOSE TO THE CONU
CONSENSUS MODEL FOR THE FIRST 72 HR AND THEN FOLLOWS THE CONSENSUS
OF THE BAM MODELS THEREAFTER.

ANALYSES FROM CIMMS AT THE UNIVERSITY OF WISCONSIN SHOW THAT GILMA
IS ENCOUNTERING 20 KT OF EASTERLY VERTICAL WIND SHEAR.  LARGE-SCALE
MODELS FORECAST THIS SHOULD CONTINUE FOR ABOUT 48 HR BEFORE
DECREASING.  BY THAT TIME...GILMA SHOULD BE OVER GRADUALLY COOLER
SEA SURFACE TEMPERATURES.  THUS...THE INTENSITY FORECAST CALLS FOR
LITTLE CHANGE IN STRENGTH...ALTHOUGH IT CANNOT BE RULED OUT THAT A
CONVECTIVE BURST COULD CAUSE GILMA TO REGAIN TROPICAL STORM
STRENGTH.  THE CYCLONE IS FORECAST TO WEAKEN OVER COOLER WATER
AFTER 72 HR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/2100Z 15.0N 107.2W    30 KT
 12HR VT     03/0600Z 15.4N 108.1W    30 KT
 24HR VT     03/1800Z 16.0N 109.5W    30 KT
 36HR VT     04/0600Z 16.9N 110.7W    30 KT
 48HR VT     04/1800Z 17.6N 112.0W    30 KT
 72HR VT     05/1800Z 19.0N 114.5W    30 KT
 96HR VT     06/1800Z 20.0N 117.5W    25 KT
120HR VT     07/1800Z 21.1N 120.5W    25 KT...DISSIPATING
 
$$
FORECASTER BEVEN
 
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