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TROPICAL STORM IRWIN DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT SAT OCT 09 1999
 
RADAR DATA FROM CUYUTLAN MEXICO THIS MORNING INDICATES THAT IRWIN
CONTINUES TO TURN AND IS NOW MOVING AT 285/3.  IF THIS MOTION AWAY
FROM THE COAST CONTINUES THEN THE TROPICAL STORM WARNINGS WILL
LIKELY BE DISCONTINUED WITH THE NEXT ADVISORY PACKAGE. RIDGING OVER
THE SOUTHWESTERN UNITED STATES AND NORTHERN MEXICO IS EXPECTED TO
KEEP IRWIN ON A GENERALLY WESTWARD TRACK FOR THE NEXT THREE DAYS. 
THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IN
CLOSE AGREEMENT WITH THE UKMET MODEL.  MOST OF THE OTHER GUIDANCE IS
FASTER TO THE WEST. 

THE CENTER APPEARS TO BE LOCATED ON THE EASTERN EDGE OF THE DEEP
CONVECTION.  DVORAK INTENSITY ESTIMATES REMAIN AT 55 AND 45 KT FROM
TAFB AND SAB RESPECTIVELY AND THE OFFICIAL INTENSITY IS HELD AT 45
KT.  THE SHIPS INTENSITY MODEL FORECASTS THAT IRWIN WILL APPROACH 
HURRICANE STRENGTH AS THE SHEAR LESSENS OVER THE NEXT 24-36 HOURS. 
THE OFFICIAL FORECAST ALLOWS SOME MODEST INCREASE IN INTENSITY BUT
NOT QUITE AS MUCH AS SHIPS.  AFTER 36 HOURS...COOLER TEMPERATURES
SHOULD BEGIN TO LIMIT DEEP CONVECTION AND SPIN DOWN THE VORTEX.

FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     09/1500Z 18.8N 106.3W    45 KTS
12HR VT     10/0000Z 18.9N 106.8W    50 KTS
24HR VT     10/1200Z 19.2N 107.8W    55 KTS
36HR VT     11/0000Z 19.4N 109.2W    55 KTS
48HR VT     11/1200Z 19.5N 110.5W    50 KTS
72HR VT     12/1200Z 19.5N 113.5W    45 KTS
 
 
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