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