ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM DARBY DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 AM PDT TUE JUL 27 2004 SATELLITE IMAGES INDICATE THAT THE CLOUD PATTERN ASSOCIATED WITH DARBY IS GRADUALLY IMPROVING. THERE IS A WELL DEFINED CONVECTIVE CURVED BAND TO THE WEST AND DEEP CONVECTION NEAR THE CENTER. THE UPPER-LEVEL OUTFLOW IS WELL ESTABLISHED AND IT IS MOST PRONOUNCED ON THE WESTERN SEMICIRCLE. DVORAK T-NUMBERS FROM TAFB AND SAB SUGGEST THAT THE WINDS ARE ALREADY 55 KNOTS. DARBY IS EXPECTED TO BE OVER WARM WATERS AND LOW SHEAR FOR THE NEXT 2 TO 3 DAYS. THEREFORE...THE CHANCES OF BECOMING A HURRICANE AND THEN FURTHER STRENGTHENING ARE HIGH. THIS IS CONSISTENT WITH SHIPS AND GFDL MODELS. DARBY IS MOVING 290 DEGREES AT 12 KNOTS AROUND THE PERIPHERY OF A SUBTROPICAL RIDGE WHICH HAS A WEAKNESS TO ITS WEST. THIS PATTERN IS FORECAST TO GRADUALLY MOVE WESTWARD AS INDICATED BY MOST OF THE GLOBAL MODELS. THIS WOULD ALLOW DARBY TO MOVE WEST OR WEST-NORTHWESTWARD DURING THE NEXT 3 TO 5 DAYS. THE OFFICIAL FORECAST IS A LITTLE BIT TO THE SOUTH OF THE MODEL CONSENSUS AS IN PREVIOUS FORECASTS. I WAS TEMPTED TO SHIFT THE OFFICIAL FORECAST NORTHWARD TO BE IN AGREEMENT WITH THE CONSENSUS BUT I RATHER WAIT FOR TODAYS EVOLUTION OF THE CYCLONE TO MAKE A CHANGE IN THE FORECAST. FORECASTER AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 27/1500Z 13.4N 118.7W 55 KT 12HR VT 28/0000Z 14.0N 120.5W 65 KT 24HR VT 28/1200Z 14.7N 123.0W 75 KT 36HR VT 29/0000Z 15.3N 125.5W 85 KT 48HR VT 29/1200Z 16.0N 127.5W 85 KT 72HR VT 30/1200Z 16.5N 131.0W 75 KT 96HR VT 31/1200Z 17.0N 135.5W 65 KT 120HR VT 01/1200Z 17.0N 139.5W 65 KT $$ NNNN
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Page last modified: Tuesday, 27-Jul-2004 14:32:27 UTC