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TROPICAL STORM ERNESTO DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT SAT SEP 02 2000
 
EARLY VISIBLE IMAGERY SHOWS A NOT-WELL-DEFINED LOW LEVEL CENTER JUST
SOUTHWEST OF A CDO TYPE FEATURE.  THE INITIAL POSITION IS RELOCATED
NORTHWARD.  THE INITIAL MOTION ESTIMATE IS 290/13.  THE GFDL AND
UKMET MODELS HAVE SHIFTED A LITTLE NORTHWARD AND SO DOES THE
OFFICIAL FORECAST WHICH REMAINS AT THE LEFT SIDE OF THE ENSEMBLE OF
GUIDANCE MODELS.  THIS REDUCES THE THREAT TO THE NORTHEASTERN
CARIBBEAN ISLANDS.  AN IMPORTANT STEERING MECHANISM IS A COLD UPPER
TROUGHLOW TO THE NORTHWEST OF THE STORM WHICH IS FORECAST TO MOVE
WESTWARD TO NEAR THE BAHAMAS IN THREE DAYS.  THE NORTHWARD SHIFT OF
THE MODELS IS IN RESPONSE TO THE STEERING ON THE EAST SIDE OF THIS
TROUGH.

THE INITIAL WIND SPEED REMAINS AT 35 KNOTS...WHICH ARE THE SATELLITE
INTENSITY ESTIMATES FROM TAFB...SAB...AND KGWC.  THE SHIPS MODEL
SHOWS AN INCREASE IN VERTICAL SHEAR FROM 06Z TO 12Z FROM 20 TO 29
KNOTS AND INCREASING.  THE INENSITY FORECAST IS CONSERVATIVELY
DECREASED BY 5 KNOTS BASED ON THIS SHEAR.  IN FACT...IF THE LOW
LEVEL CENTER ON VISIBLE IMAGERY CONTINUES TO BE SHEARED AWAY FROM
THE DEEP CONVECTION...ERNESTO COULD WEAKEN TO A DEPRESSION.  HOWEVER
IN CONTRAST...THE SHIPS MODEL STILL CALLS FOR SOME STRENGTHENING
BASED ON AN OTHERWISE FAVORABLE ENVIRONMENT. 
 
FORECASTER LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     02/1500Z 17.4N  51.6W    35 KTS
12HR VT     03/0000Z 18.1N  53.5W    35 KTS
24HR VT     03/1200Z 19.0N  56.2W    40 KTS
36HR VT     04/0000Z 20.0N  58.7W    40 KTS
48HR VT     04/1200Z 21.0N  61.2W    40 KTS
72HR VT     05/1200Z 22.5N  65.2W    40 KTS
  
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