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TROPICAL STORM IRWIN DISCUSSION NUMBER   2
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT FRI OCT 08 1999
 
RADAR DATA FROM CUYUTLAN MEXICO CLEARLY REVEAL A TIGHT CENTER WITH
BANDING FEATURES.  THERE IS A CLUSTER OF DEEP CONVECTION NEAR THE
CENTER AND T-NUMBERS ARE 3.0 AND 2.5 ON THE DVORAK SCALE.  BASED ON
THIS INFORMATION...THE TROPICAL DEPRESSION IS BEING UPGRADED TO
TROPICAL STORM IRWIN AT THIS TIME.  THERE IS SOME EASTERLY SHEAR
OVER THE SYSTEM...SO ONLY SLIGHT STRENGTHENING IS INDICATED BEFORE
IRWIN REACHES COOL WATERS IN 48 HOURS OR SO.

IRWIN HAS BEEN MOVING NORTHWARD BETWEEN 5 AND 8 KNOTS TOWARD THE
COAST OF MEXICO DURING THE PAST FEW HOURS.  HOWEVER...GLOBAL MODELS
DEVELOP A STRONG RIDGE OVER THE SOUTHWESTERN UNITED STATES AND
NORTHERN MEXICO.  THIS PATTERN WOULD FORCE THE TROPICAL STORM ON A
MORE NORTHWEST MOTION SHORTLY AND THEN A WESTERLY TRACK DURING THE
NEXT FEW DAYS AS INDICATED BY TRACK GUIDANCE.  BECAUSE THIS TURN IS
EXPECTED TO OCCUR VERY CLOSE TO THE SOUTHWEST COAST OF MEXICO...A
TROPICAL STORM WARNING HAS BEEN ISSUED FOR A PORTION OF THE COAST.

AVILA 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     09/0300Z 18.5N 105.2W    40 KTS
12HR VT     09/1200Z 19.3N 105.4W    45 KTS
24HR VT     10/0000Z 20.0N 106.5W    50 KTS
36HR VT     10/1200Z 20.5N 108.0W    50 KTS
48HR VT     11/0000Z 20.5N 110.0W    40 KTS
72HR VT     12/0000Z 20.5N 114.5W    30 KTS
 
 
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