ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM 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 NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:42 UTC