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TROPICAL STORM ERIN DISCUSSION NUMBER  12
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT TUE SEP 04 2001
 
THE LOW-LEVEL CENTER OF ERIN IS VERY DIFFICULT TO LOCATE ON 
SATELLITE IMAGERY. IT IS ASSUMED....MAINLY BY CONTINUITY...THAT IT 
IS LOCATED SOUTHWEST OF THE SHAPELESS CLOUD MASS THAT ACCOMPANIES 
THE TROPICAL CYCLONE. THE CENTER MAY HAVE TO BE RELOCATED LATER ON 
WHEN LONGER VISIBLE LOOPS BECOME AVAILABLE OR IF IT BECOMES EXPOSED. 
SATELLITE INTENSITY ESTIMATES FROM ALL AGENCIES SUGGEST THAT WINDS 
ARE 45 KNOTS.  EVERY AVAILABLE FORECAST TOOL SUGGESTS THAT SHEAR 
WILL RELAX AND THAT THE UPPER LOW AHEAD OF ERIN WILL WEAKEN. 
HOWEVER...WATER VAPOR IMAGES STILL SHOW STRONG SOUTHWESTERLY SHEAR 
AHEAD AND OVER THE SYSTEM AND THAT THE UPPER LOW IS INTACT AT THIS 
TIME.  PREVIOUS FORECAST SHOWS GRADUAL INTENSIFICATION. ALTHOUGH 
DOUBTFUL... BECAUSE THE SHEAR IS PRESENT...FOR THE SAKE OF 
CONTINUITY...A GRADUAL STRENGTHENING IS INDICATED IN THIS FORECAST. 

ERIN HAS JOGGED TEMPORARILY WESTWARD ABOUT 16 KNOTS.  THERE IS A
SOLID 500 MB RIGDE TO THE NORTH WHICH SUPPORTS A GENERAL WEST TO
WEST-NORTHWEST TRACK DURING THE NEXT 24 TO 36 HOURS.  THEREAFTER
...STEERING CURRENTS ARE EXPECTED TO WEAKEN AND ERIN SHOULD DECREASE
IN FORWARD SPEED AND TURN MORE TO THE NORTHWEST.  BY THEN...THE
TROPICAL CYCLONE SHOULD BE NORTH OF THE LEEWARD ISLANDS.  THIS
FORECAST IS WITHIN THE TRACK ENSEMBLE.  ONLY THE UK MODEL TURNS ERIN
NORTHWARD.

THE TRUTH WILL BE KNOWN TOMORROW WHEN AN AIR FORCE PLANE REACHES
THE TROPICAL CYCLONE.

FORECASTER AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     04/1500Z 17.1N  53.1W    45 KTS
12HR VT     05/0000Z 17.5N  55.5W    45 KTS
24HR VT     05/1200Z 18.5N  58.0W    45 KTS
36HR VT     06/0000Z 20.0N  60.0W    55 KTS
48HR VT     06/1200Z 21.5N  61.5W    60 KTS
72HR VT     07/1200Z 23.0N  63.5W    65 KTS
 
 
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