000
WTPZ41 KNHC 130233
TCDEP1
 
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