Tropical Storm IRWIN

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TROPICAL STORM IRWIN DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 AM PDT FRI AUG 26 2005

LATEST GOES-10 AND GOES-12 SATELLITE IMAGERY AND A 0518Z AMSU PASS
INDICATE THE CIRCULATION CENTER VERY CLOSE TO THE DEEP CONVECTION. 
BASED ON DVORAK T NUMBERS OF 2.5 OR 35 KT FROM BOTH TAFB AND SAB
AND UNCONTAMINATED 35-40 KT WINDS FROM A 01Z QUIKSCAT PASS...T.D.
NINE HAS BEEN UPGRADED TO TROPICAL STORM IRWIN. CURRENTLY THE STORM
IS ENCOUNTERING NORTHEASTERLY SHEAR BUT THIS SHEAR IS FORECAST TO
RELAX A BIT IN THE NEXT 24-36 HOURS...PERHAPS ALLOWING IRWIN TO
INTENSIFY TO A 50 KT STORM IN 36 HOURS.  THE OFFICIAL INTENSITY
FORECAST FOLLOWS CLOSELY WITH THE SHIPS GUIDANCE HOWEVER HOLDS
IRWIN TO 50 KT BASED ON THE LOCATION OF THE FORECAST TRACK RELATIVE
TO THE 26 DEGREE CELSIUS ISOTHERM.  BEYOND TWO DAYS...THE CYCLONE
SHOULD MOVE OVER COOLER WATERS WITH DISSIPATION STILL EXPECTED IN
120 HOURS. 

THE INITIAL MOTION REMAINS 280/10. IRWIN IS SOUTH OF A MID-LEVEL
RIDGE THAT IS FORECAST TO BUILD WESTWARD OVER THE NEXT FEW DAYS...
AND THIS SHOULD KEEP THE SYSTEM ON AN OVERALL WESTERLY TRACK.  THE
GFDL...UKMET...AND NOGAPS MODELS DISSIPATE IRWIN IN TWO TO THREE
DAYS WHILE THE GFS MAINTAINS A CIRCULATION AND FORECASTS THE STORM
TO MOVE TO THE WEST-SOUTHWEST THROUGH FIVE DAYS. THE OFFICIAL
FORECAST IS A BLEND OF THE PREVIOUS FORECAST AND THE GFS GUIDANCE. 
 
FORECASTER MAINELLI/KNABB
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0900Z 17.5N 108.2W    35 KT
 12HR VT     26/1800Z 17.8N 109.6W    40 KT
 24HR VT     27/0600Z 18.0N 111.6W    45 KT
 36HR VT     27/1800Z 18.2N 113.6W    50 KT
 48HR VT     28/0600Z 18.3N 115.5W    50 KT
 72HR VT     29/0600Z 18.2N 119.1W    45 KT
 96HR VT     30/0600Z 18.0N 123.0W    40 KT
120HR VT     31/0600Z 18.0N 126.0W    30 KT...DISSIPATING
 
 
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