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HURRICANE ALMA DISCUSSION NUMBER  27
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT FRI MAY 31 2002

THE CONVECTIVE PATTERN ASSOCIATED WITH ALMA HAS BECOME FRAGMENTED
OVER THE PAST SEVERAL HR...AND THERE ARE HINTS IN BOTH MICROWAVE
AND INFRARED IMAGERY THAT THE CENTER IS BECOMING EXPOSED ON THE
WEST SIDE OF THE CONVECTION DUE TO SHEAR.  THE MAXIMUM WINDS ARE
REDUCED TO 80 KT IN THIS PACKAGE BASED ON SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB.  HOWEVER...IF THE CENTER IS SEPARATING
FROM THE CONVECTION THIS MAY BE GENEROUS.
 
GIVEN THE USUAL PROBLEMS OF FINDING A PARTLY EXPOSED LOW LEVEL
CENTER AT NIGHT...THE INITIAL POSITION IS BASED ON THE EASTERNMOST
OF THE SATELLITE FIXES.  THIS GIVES AN INITIAL MOTION ESTIMATE
OF 360/6.  WATER VAPOR IMAGERY INDICATES THE UPPER LEVEL LOW
NEAR 30N121W IS MOVING NORTHWARD...WHICH IS LEAVING ALMA TRAPPED
IN THE NORTHERN PORTION OF THE BUILDING SUBTROPICAL RIDGE.  MODEL
GUIDANCE MOSTLY RESPONDS TO THIS BY FORECASTING A SLOW TURN TOWARD
THE EAST DURING THE FORECAST PERIOD.  THE BAMS AND BAMM ARE THE 
EXCEPTIONS...CALLING FOR A SLOW NORTHWESTWARD MOTION.  RIGHT NOW...
THE OFFICIAL FORECAST FOLLOWS THE EASTWARD TURNING MODELS AND
IS A LITTLE SLOWER THAN THE PREVIOUS FORECAST.  IT SHOULD BE NOTED
THAT IF THE LOW LEVEL CENTER IS BECOMING EXPOSED WHERE IT APPEARS
TO BE IN IR IMAGERY...THIS INDICATES A WESTWARD OR WEST-
NORTHWESTWARD MOTION THAT IS NOT CURRENTLY SUPPORTED BY ANY 
GUIDANCE.
 
ALMA IS NOW OVER 24C-25C SEA SURFACE TEMPERATURES AND IS UNDER
15-20 KT OF SOUTHWESTERLY SHEAR.  THE COMBINATION...WHICH SHOULD
PERSIST THROUGH THE FORECAST PERIOD...IS CAUSING THE CYCLONE TO
WEAKEN.  THE WEAKENING TREND TREND SHOULD CONTINUE UNTIL DISSIPATION
IN ABOUT 72 HR.
 
IF VISIBLE IMAGERY CONFIRMS THAT THE LOW LEVEL CENTER IS MOVING
MORE NORTHWESTWARD OR WESTWARD...SIGNIFICANT REVISIONS IN BOTH
THE TRACK AND INTENSITY FORECASTS WILL BE REQUIRED IN THE NEXT
PACKAGE.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     31/0900Z 18.2N 115.1W    80 KTS
12HR VT     31/1800Z 18.7N 115.1W    70 KTS
24HR VT     01/0600Z 19.3N 114.8W    55 KTS
36HR VT     01/1800Z 19.7N 114.3W    40 KTS
48HR VT     02/0600Z 19.9N 113.7W    30 KTS
72HR VT     03/0600Z 20.0N 113.0W    25 KTS...DISSIPATING
 
 
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