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TROPICAL DEPRESSION ISELLE DISCUSSION NUMBER  20
NATIONAL WEATHER SERVICE MIAMI FL
2 PM PDT THU SEP 19 2002
 
SEVERAL SHIPS REPORTED FROM NEAR THE CENTER OF ISELLE AT 18Z...
INCLUDING ONE WITH 22 METERS PER SECOND...43 KT...AND 5 FT SEAS. 
THE WINDS LOOK SUSPECT GIVEN THE LOW SEAS HEIGHTS AND THE OTHER
TWO SHIPS REPORTING 15 AND 10 KT RESPECTIVELY.  A RECENT SSM/I
OVERPASS INDICATED NO WINDS HIGHER THAN 25 KT OUTSIDE OF THE
REMAINING CONVECTION.  SATELLITE INTENSITY ESTIMATES ARE 35 KT
FROM SAB AND 30 KT FROM TAFB AND AFWA.  BASED ON ALL THIS...
ISELLE IS DOWNGRADED TO A 30 KT DEPRESSION.  THE CENTRAL PRESSURE
OF 1004 MB IS BASED ON THE SHIP REPORTS.

THE INITIAL MOTION IS 045/5.  ISELLE REMAINS IN A WEAK STEERING
FLOW ENVIRONMENT...WITH WATER VAPOR IMAGERY INDICATING AN UPPER-
LEVEL LOW DEVELOPING JUST WEST OF THE CYCLONE.  GUIDANCE IS SPLIT
INTO TWO CAMPS...WITH A GROUP INCLUDING CLIPER...LBAR...NHC91...
AND BAMD FORECASTING A NORTHEASTWARD MOTION AND A SECOND GROUP...
INCLUDING THE NOGAPS...UKMET...AND GDFL...TURNING THE CYCLONE
NORTHWESTWARD.  THE OFFICIAL FORECAST WILL FOLLOW THE PREVIOUS
PACKAGE AND CALL FOR A TURN TO THE NORTHWEST AFTER 12 HR.
 
WHILE ISELLE IS STILL PRODUCING CONVECTION...THERE IS VERY LITTLE
ORGANIZATION TO IT DUE TO SHEAR BY THE UPPER LEVEL LOW.  WHILE
ISELLE IS LIKELY TO PRODUCE A FEW MORE BURST OF DISORGANIZED
CONVECTION...THE CYCLONE SHOULD CONTINUE TO SLOWLY WEAKEN UNTIL
DISSIPATION AFTER 36 HR.
 
FORECASTER BEVEN/MAINELLI
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     19/2100Z 24.0N 112.4W    30 KTS
12HR VT     20/0600Z 24.4N 112.3W    25 KTS...DISSIPATING
24HR VT     20/1800Z 25.0N 112.8W    20 KTS...DISSIPATING
36HR VT     21/0600Z 25.6N 113.5W    20 KTS...DISSIPATING
48HR VT     21/1800Z...DISSIPATING
 
 
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