ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IRWIN DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011 200 AM PDT MON OCT 10 2011 CONVENTIONAL SATELLITE AND MICROWAVE IMAGERY SHOW A SIGNIFICANT LACK OF CORE CONVECTION WITH A FRAGMENTED CURVED BANDING STRUCTURE. DVORAK SATELLITE ESTIMATES FROM TAFB AND SAB ARE 45 AND 35 KT RESPECTIVELY...AND THE UW-CIMSS ADVANCED DVORAK TECHNIQUE ESTIMATE IS 40 KT. THE INITIAL INTENSITY IS LOWERED TO 40 KT BASED ON A BLEND OF THESE ESTIMATES. THE SHIPS...LGEM...AND THE HURRICANE FORECAST IMPROVEMENT PROJECT CONSENSUS MODEL ALL AGREE WITH LITTLE CHANGE IN STRENGTH DURING THE NEXT COUPLE OF DAYS. AT DAY 4 AND 5...THE MODELS SHOW A GRADUAL WEAKENING DUE TO AN INCREASE IN EASTERLY SHEAR. THE INTENSITY FORECAST FOLLOWS THE MODEL GUIDANCE CLOSELY AND NOW SHOWS SLIGHT WEAKENING AT DAY 5. ALTHOUGH THE BEST TRACK HAS BEEN ADJUSTED A LITTLE TO THE SOUTH OF THE PREVIOUS ADVISORY BASED ON A SERIES OF MICROWAVE IMAGES...THE INITIAL MOTION REMAINS UNCHANGED...085/5. AN EASTWARD OR POSSIBLY A LITTLE SOUTH OF EASTWARD MOTION IS FORECAST DURING THE 36 HOURS AS IRWIN TRACKS WITHIN THE FLOW TO THE EAST OF AN AMPLIFYING MID- TO UPPER-LEVEL TROUGH TO THE SOUTHWEST OF THE BAJA PENINSULA. A TURN EAST-NORTHEASTWARD WITH A DECREASE IN FORWARD SPEED AROUND THE 96 HR PERIOD IS EXPECTED IN THE WAKE OF HURRICANE JOVA...AND AN INCREASING WEAKNESS IN THE SUBTROPICAL RIDGE OVER SOUTHWESTERN MEXICO. AT THE END OF THE FORECAST PERIOD...THE ECMWF...NOGAPS... AND UKMET SHOW IRWIN AS A WEAK...SHALLOW CYCLONE THAT COMMENCES A TRACK TOWARD THE SOUTHEAST WITHIN THE NORTHWESTERLY MARINE-LAYER FLOW ALONG THE MEXICO COAST. THE GFS...HOWEVER...IS SHOWING A COMPLEX INTERACTION BETWEEN IRWIN...THE REMNANTS JOVA...AND A SHORT-WAVE TROUGH TO THE NORTHWEST. THE OFFICIAL FORECAST SIDES WITH THE FORMER SOLUTION AND IS CLOSE TO THE MULTI-MODEL CONSENSUS AND ALSO SHOWS A REDUCTION IN FORWARD SPEED. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 14.9N 118.5W 45 KT 50 MPH 12H 10/1800Z 15.0N 117.3W 45 KT 50 MPH 24H 11/0600Z 15.0N 115.8W 45 KT 50 MPH 36H 11/1800Z 14.9N 114.1W 45 KT 50 MPH 48H 12/0600Z 15.2N 112.0W 45 KT 50 MPH 72H 13/0600Z 16.5N 108.0W 45 KT 50 MPH 96H 14/0600Z 17.0N 105.5W 40 KT 45 MPH 120H 15/0600Z 16.5N 104.0W 40 KT 45 MPH $$ FORECASTER ROBERTS/BROWN NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:20 UTC