ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION IRWIN DISCUSSION NUMBER 28 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011 800 PM PDT WED OCT 12 2011 SATELLITE IMAGES INDICATE THAT IRWIN HAS WEAKENED...AND THE CYCLONE IS NOW NEARLY DEVOID OF DEEP CONVECTION. DVORAK CLASSIFICATIONS SUPPORT LOWERING THE INITIAL WIND SPEED TO 30 KT...AND THIS MAKES IRWIN A TROPICAL DEPRESSION ONCE AGAIN. GIVEN THE RECENT DECLINE IN THUNDERSTORM ACTIVITY AND BECAUSE THE SHEAR IS NOT EXPECTED TO LESSEN MUCH ON THURSDAY...IRWIN IS NOW FORECAST TO BECOME A REMNANT LOW BY 36 HOURS...BUT THIS COULD OCCUR EVEN SOONER. SOME OF THE MODELS SHOW IRWIN RESTRENGTHENING BY THE END OF THE FORECAST PERIOD. THE OFFICIAL FORECAST...HOWEVER...KEEPS IRWIN AS A REMNANT LOW BEYOND 36 HOURS DUE TO THE HIGH UNCERTAINTY AT THE LONGER TIME RANGE. IRWIN IS MOVING TO THE NORTHEAST AT ABOUT 13 KT ON THE EAST SIDE OF A CUTOFF LOW. THE DEPRESSION IS EXPECTED TO TURN TO THE EAST AND SLOW DOWN DURING THE NEXT 12 TO 24 HOURS STEERED BY THE LOW-LEVEL WESTERLY FLOW. BEYOND THAT TIME...IRWIN...OR ITS REMNANT LOW...IS EXPECTED TO MAKE A CLOCKWISE LOOP AS A LOW- TO MID-LEVEL RIDGE BUILDS TO ITS NORTH. THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE AND IS CLOSEST TO THE ECMWF MODEL AND THE HFIP MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 17.8N 108.6W 30 KT 35 MPH 12H 13/1200Z 18.2N 107.0W 30 KT 35 MPH 24H 14/0000Z 18.1N 105.3W 30 KT 35 MPH 36H 14/1200Z 17.4N 104.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 15/0000Z 16.7N 104.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 16/0000Z 16.0N 105.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 17/0000Z 16.0N 108.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 18/0000Z 16.0N 111.0W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ FORECASTER CANGIALOSI NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:19 UTC