Tropical Storm IRWIN

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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
 
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