ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IRWIN DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 AM PDT FRI AUG 26 2005 LATEST ENHANCED INFRARED IMAGERY DEPICT IRWIN AS A STRONGER TROPICAL STORM. CONVECTION REMAINS SOUTH OF THE CENTER AS NORTHEASTERLY SHEAR IMPACTS THE SYSTEM. THE INITIAL INTENSITY FOR IRWIN IS INCREASED TO 45 KT BASED ON DVORAK ESTIMATES OF 3.0 FROM TAFB AND SAB...THE UW-CIMSS OBJECTIVE DVORAK TECHNIQUE YIELDS 47 KT. THE INTENSITY FORECAST CALLS FOR IRWIN TO REMAIN A TROPICAL STORM OVER THE NEXT SEVERAL DAYS. IRWIN IS FORECAST TO REMAIN IN AN ENVIRONMENT OF RELATIVELY WARM OCEAN WATERS AND MODERATE SHEAR WHICH SHOULD ALLOW STRENGTHENING UP TO 50 KT. IN THE EXTENDED FORECAST PERIOD...THE SHEAR INCREASES AND IRWIN CROSSES BEYOND THE 26 SST DEGREE ISOTHERM SO A DECREASE IN INTENSITY TO DEPRESSION STRENGTH IS FORECAST. THE INITIAL MOTION REMAINS 280/10. IRWIN IS EXPECTED TO REMAIN SOUTH OF A MID-LEVEL RIDGE. THIS RIDGE IS FORECAST TO BUILD WESTWARD KEEPING IRWIN ON A GENERALLY WESTWARD TRACK OVER THE NEXT SEVERAL DAYS. THE OFFICIAL FORECAST TRACK FOLLOWS THE CONSENSUS MODELS OUT TO 72 HRS. BEYOND 72 HOURS...THE FORECAST TRACK IS A BLEND OF THE FSSE AND GFS TRACKS THAT KEEP IRWIN TRACKING WESTWARD. THE CONSENSUS MODELS AND GFDL IN THE LATE PERIOD TRACK IRWIN ON A NORTHWARD TRACK. THE OFFICIAL TRACK FORECAST CALLS FOR CONTINUED WESTWARD MOTION ALONG THE SOUTHERN EXTENT OF THE MID-LEVEL RIDGE. FORECASTER SISKO/STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 26/1500Z 17.8N 109.2W 45 KT 12HR VT 27/0000Z 18.0N 110.7W 45 KT 24HR VT 27/1200Z 18.1N 112.6W 50 KT 36HR VT 28/0000Z 18.3N 114.6W 50 KT 48HR VT 28/1200Z 18.3N 116.4W 50 KT 72HR VT 29/1200Z 18.2N 120.1W 50 KT 96HR VT 30/1200Z 18.0N 123.5W 40 KT 120HR VT 31/1200Z 17.5N 126.5W 30 KT...DISSIPATING $$ NNNN
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Page last modified: Friday, 26-Aug-2005 15:10:13 UTC