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TROPICAL STORM ERIN DISCUSSION NUMBER  16
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT WED SEP 05 2001

ERIN IS A SHEARED SYSTEM ON A WEAKENING TREND.  AN AIR FORCE PLANE 
REACHED THE CENTER OF ERIN THIS MORNING AND FOUND A POORLY DEFINED 
CIRCULATION WITH A 1013 MB AND 1015 MB MINIMUM PRESSURE. FLIGHT 
LEVEL WINDS WERE 49 KNOTS BUT LIMITED TO THE EAST OF THE 
CIRCULATION. THIS IS IN AGREEMENT WITH VISIBLE SATELLITE IMAGES 
WHICH SHOW AN EXPOSED CENTER TO THE WEST OF THE CONVECTION.  INITIAL 
INTENSITY HAS BEEN LOWERED TO 40 KNOTS AT THIS TIME.  WATER VAPOR 
IMAGES SUGGEST THAT THE UPPER-LOW AHEAD OF ERIN IS STILL THERE AND 
THE TENDENCY INDICATED BY MODELS FOR THE UPPER-LOW TO WEAKEN HAS NOT 
MATERIALIZED SO FAR.  TO BE CONSERVATIVE ...THE INTENSITY FORECAST 
IS KEEPING A 40-KNOT TROPICAL CYCLONE THROUGH THE FORECAST PERIOD.  
HOWEVER...THESE TYPE OF SHEARED SYSTEMS OCCASIONALLY RECOVER...BUT 
MOST OF THE TIME DO NOT. BOTH SHIPS AND THE GFDL OPTED FOR THE 
RECOVERY AND MAKE ERIN A HURRICANE....NOT THE OFFICIAL FORECAST 

ERIN HAS SLOWED DOWN AND IS MOVING WEST-NORTHWEST ABOUT 10 KNOTS. 
THIS IS BASED ON THE SMALL ADJUSTMENT IN THE INITIAL LOCATION 
PROVIDED BY THE AIRCRAFT.  STEERING CURRENTS ARE FORECAST TO WEAKEN 
AND ERIN IS FORECAST TO CONTINUE ON THE SAME GENERAL TRACK WITH A 
SIGNIFICANT DECREASE IN FORWARD SPEED DURING THE NEXT 3 DAYS. MOST 
OF THE WEATHER ASSOCIATED WITH ERIN IS EXPECTED TO PASS WELL NORTH 
OF THE LEEWARD ISLANDS.

THE SHORT TERM FORECAST IS ALREADY VERY COMPLICATED SO I WOULD 
RATHER NOT SPECULATE ON THE LONGER RANGE AT THIS TIME. 

FORECASTER AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     05/1500Z 18.3N  57.5W    40 KTS
12HR VT     06/0000Z 18.6N  59.0W    40 KTS
24HR VT     06/1200Z 19.5N  60.5W    40 KTS
36HR VT     07/0000Z 20.5N  62.0W    40 KTS
48HR VT     07/1200Z 21.0N  63.0W    40 KTS
72HR VT     08/1200Z 22.5N  64.0W    40 KTS
 
 
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