000 WTPZ41 KNHC 062033 TCDEP1 TROPICAL STORM IRWIN DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011 200 PM PDT THU OCT 06 2011 WELL...SO MUCH FOR THE SLOW STRENGTHENING THAT WAS FORECAST IN THE PREVIOUS ADVISORY. IRWIN HAS BECOME CONSIDERABLY BETTER ORGANIZED OVER THE PAST SEVERAL HOURS...WITH WELL-DEFINED CURVED BAND FEATURES WRAPPING AROUND THE CENTER. DVORAK INTENSITY ESTIMATES RANGE FROM 45 TO 55 KT FROM SAB AND TAFB...RESPECTIVELY...AND THE INITIAL WIND SPEED IS SET TO 50 KT. UPPER-LEVEL OUTFLOW HAS BECOME BETTER-DEFINED AND IS EXPANDING. IT NOW APPEARS THAT...IN COMPARISON TO THE TROPICAL CYCLONE LOCATED ABOUT 10 DEGREES TO THE EAST...IRWIN IS THE DOMINANT SYSTEM. THIS IMPLIES THAT THE CIRCULATION OF THE EASTERN CYCLONE WILL NOT HAVE MUCH OF AN ADVERSE IMPACT...AND THE OFFICIAL FORECAST NOW SHOWS IRWIN STRENGTHENING INTO A HURRICANE. THIS IS SIMILAR TO THE STATISTICAL-DYNAMICAL GUIDANCE AND TO THE INTENSITY MODEL CONSENSUS. THE STORM HAS MOVED A LITTLE FASTER TOWARD THE WEST-NORTHWEST...OR 295/7...OVER THE PAST FEW HOURS. A MID-LEVEL RIDGE TO THE NORTHEAST OF IRWIN IS FORECAST TO RETREAT AS A DEEP-LAYER TROUGH DEVELOPS TO THE NORTH OF THE TROPICAL CYCLONE. IN RESPONSE TO THIS EVOLUTION OF THE STEERING PATTERN...IRWIN IS EXPECTED TO TURN TOWARD THE RIGHT AND DECELERATE OVER THE NEXT COUPLE OF DAYS. LATER IN THE FORECAST PERIOD...IRWIN SHOULD MOVE EAST-NORTHEASTWARD TOWARD MEXICO IN THE FLOW TO THE SOUTH OF THE TROUGH. THE LATEST OFFICIAL FORECAST IS A LITTLE FASTER THAN THE PREVIOUS ONE. THIS IS BETWEEN THE SIGNIFICANTLY FASTER GFS...GFDL...AND HWRF GUIDANCE AND THE SLOWER ECMWF FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 12.8N 117.9W 50 KT 60 MPH 12H 07/0600Z 12.9N 118.4W 55 KT 65 MPH 24H 07/1800Z 13.6N 118.5W 60 KT 70 MPH 36H 08/0600Z 13.9N 118.0W 65 KT 75 MPH 48H 08/1800Z 14.1N 117.4W 70 KT 80 MPH 72H 09/1800Z 14.5N 115.5W 80 KT 90 MPH 96H 10/1800Z 15.5N 113.0W 80 KT 90 MPH 120H 11/1800Z 16.5N 111.0W 80 KT 90 MPH $$ FORECASTER PASCH