HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

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TROPICAL STORM IRWIN DISCUSSION NUMBER   8
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT SUN OCT 10 1999
 
THE LOW-LEVEL CIRCULATION CENTER OF IRWIN IS ON THE NORTHEAST EDGE
OF THE DEEP CONVECTION...AND COLD CLOUD TOPS CONTINUE TO WARM AS THE
CYCLONE BEGINS ITS DECAY PHASE.  SATELLITE INTENSITY ESTIMATES...
CONSTRAINED BY THE DVORAK CLASSIFICATION RULES...ARE 55 AND 35 KT
FROM TAFB AND SAB RESPECTIVELY.  THE INITIAL INTENSITY IS HELD AT 45
KT FOR THIS ADVISORY.  SSTS WILL DECREASE ONLY MODESTLY ALONG THE
FORECAST TRACK...AND AS A RESULT THE SHIPS INTENSITY FORECAST MODEL
KEEPS IRWIN AS A TROPICAL STORM THROUGH 72 HOURS.  GIVEN THE LIMITED
CONVECTION AND SMALL SIZE OF THE CYCLONE...THE OFFICIAL FORECAST
DECAYS THE SYSTEM MORE RAPIDLY THAN THE SHIPS GUIDANCE.
 
IRWIN CONTINUES TO BE STEERED BY A DEEP-LAYER MEAN EASTERLY FLOW
PRODUCED BY A HIGH OVER THE SOUTHWESTERN UNITED STATES AND NORTHERN
MEXICO.  THE INITIAL MOTION REMAINS 275/9.  THE TRACK MODELS AGREE
ON A WESTWARD TRACK THROUGH THE FORECAST PERIOD.  THE UKMET MODEL
APPEARS TO LOSE THE VORTEX AFTER 36 HOURS.  THE OFFICIAL FORECAST IS
SIMILAR TO...BUT SLIGHTLY FASTER THAN THE PREVIOUS ADVISORY.

FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     10/1500Z 19.2N 110.5W    45 KTS
12HR VT     11/0000Z 19.2N 112.0W    40 KTS
24HR VT     11/1200Z 19.2N 114.0W    35 KTS
36HR VT     12/0000Z 19.2N 116.3W    30 KTS
48HR VT     12/1200Z 19.5N 118.5W    25 KTS...DISSIPATING
72HR VT     13/1200Z 20.0N 122.5W    20 KTS...DISSIPATING
 
 
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