Tropical Depression GILMA

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TROPICAL DEPRESSION GILMA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP082006
800 AM PDT WED AUG 02 2006
 
EASTERLY SHEAR CONTINUES TO TAKE ITS TOLL ON GILMA WITH THE
LOW-LEVEL CIRCULATION BECOMING COMPLETELY EXPOSED OVERNIGHT. OVER
THE LAST FEW HOURS...A NEW BURST OF CONVECTION HAS FORMED TO THE
WEST OF THE CENTER.  BASED ON THIS BURST AND UNCHANGED SATELLITE
INTENSITY ESTIMATES...THE INITIAL INTENSITY IS HELD AT 30 KT. THE
INTENSITY FORECAST IS PROBLEMATIC AS THE SHIPS MODEL FORECAST
VERTICAL SHEAR TO REMAIN STRONG BUT THE SST SUFFICIENTLY WARM. THIS
ENVIRONMENT WOULD TEND TO ALLOW THE BURSTING PATTERN TO CONTINUE
WHERE DEEP CONVECTION FORMS OVER OR NEAR THE CENTER THEN GETS BLOWN
OFF TO THE WEST.  ACCORDINGLY...THE OFFICIAL FORECAST IS UNCHANGED
FROM THE PREVIOUS ADVISORY AND MAINTAINS A 30 KT DEPRESSION
THROUGHOUT THE ENTIRE FORECAST.  HOWEVER...IT IS NOT OUT OF THE
QUESTION THAT A CONVECTIVE BURST COULD CAUSE GILMA TO BRIEFLY
REGAIN ITS FORMER TROPICAL STORM STATUS.
 
GIVEN THE AFOREMENTIONED EVOLUTION OF THE CONVECTION...THE MOTION IS
ERRATIC. THE SHORT-TERM MOTION IS ESTIMATED TO BE MORE TOWARDS THE
WEST AT 285/04 WHILE THE LONGER-TERM MOTION IS 300/04.  GIVEN THE
PRESENT BURSTING SCENARIO...THE LATER IS FELT TO BE A MORE RELIABLE
INITIAL MOTION ESTIMATE. THE TRACK FORECAST IS EQUALLY AS
CHALLENGING AS THE INTENSITY FORECAST DUE IN PART TO THE
UNCERTAINTY ON THE EVENTUAL DEPTH OF THE CYCLONE. ADDITIONALLY...
GLOBAL MODELS DIFFER IN THE EVOLUTION OF A LARGE TROUGH AMPLIFYING
OFF THE WEST COAST OF THE UNITED STATES.  THE GFS AND GFS ENSEMBLE
MEAN SHOW LESS AMPLIFICATION ALLOWING A RIDGE TO DEVELOP NORTH OF
THE CYCLONE THUS IMPARTING A MORE WESTWARD MOTION.  CONVERSELY...
THE UKMET SHOWS A DEEPER TROUGH...WEAKER RIDGING NORTH OF THE
DEPRESSION...AND A GRADUAL TURN TOWARDS THE NORTH.  SHOULD THE
BURSTING OF CONVECTION CONTINUE...THE CYCLONE WOULD TEND TO STAIR
STEP ITS WAY IN A GENERAL NORTHWESTWARD MOTION AROUND THE WESTERN
PERIPHERY OF A RIDGE OVER CENTRAL MEXICO. ONLY MINOR ADJUSTMENTS
ARE MADE TO THE OFFICIAL FORECAST. 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/1500Z 14.9N 106.5W    30 KT
 12HR VT     03/0000Z 15.2N 107.3W    30 KT
 24HR VT     03/1200Z 15.7N 108.7W    30 KT
 36HR VT     04/0000Z 16.3N 110.0W    30 KT
 48HR VT     04/1200Z 17.2N 111.5W    30 KT
 72HR VT     05/1200Z 18.2N 113.7W    30 KT
 96HR VT     06/1200Z 19.5N 117.0W    30 KT
120HR VT     07/1200Z 20.5N 119.5W    30 KT
 
$$
FORECASTER RHOME/PASCH
 
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