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HURRICANE ALMA DISCUSSION NUMBER  22
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT WED MAY 29 2002
 
THERE IS A BIT OF A DILEMMA IN DETERMINING JUST HOW STRONG ALMA
ACTUALLY IS.  SATELLITE IMAGERY DURING THE PAST 3 HOURS INDICATES
THE INNER CORE CONVECTION AND EYE HAVE BECOME MUCH BETTER DEFINED.
DVORAK SATELLITE INTENSITY ESTIMATES ARE T5.5...102 KT...AND
T5.0...90 KT...FROM TAFB AND SAB...RESPECTIVELY...DATA-T NUMBERS ARE
T6.0...115 KT...FROM TAFB AND THE OBJECTIVE DVORAK TECHNIQUE.
HOWEVER...EXPERIENCE HAS SHOWN THAT SATELLITE INTENSITY ESTIMATES
ARE TYPICALLY ONE-HALF T-NUMBER TOO HIGH WITH DEVELOPING NORTHEAST
PACIFIC TROPICAL CYCLONES...SO THE INITIAL INTENSITY ESTIMATE IS
ONLY INCREASED TO 90 KT AT THIS TIME.  THIS IS ALSO CONSISTENT WITH
THE 90 KT...OR T5.0...3-HOUR ODT AVERAGE INTENSITY.  UPPER-LEVEL
OUTFLOW REMAINS FAIRLY IMPRESSIVE...BUT IS BEGINNING TO BECOME
ELONGATED IN A NORTH-SOUTH ORIENTATION.
 
THE INITIAL MOTION IS 360/7.  IT APPEARS THAT ALMA HAS FINALLY MADE
THE TURN TO THE NORTH AND IS PASSING THROUGH THE SUBTROPICAL RIDGE.
SINCE THE CYCLONE IS ON TRACK...THERE IS NO SIGNIFICANT CHANGE TO
PREVIOUS FORECAST TRACK OR REASONING.  WATER VAPOR IMAGERY INDICATES
THE UPPER-LEVEL LOW WEST OF THE BAJA SPUR HAS STARTED TO LIFT OUT TO
THE NORTH.  THIS SHOULD ALLOW THE SUBTROPICAL RIDGE TO SHIFT
SLIGHTLY NORTHWARD...ALLOWING ALMA TO MAKE MORE OF A GRADUAL OR
SQUARED-OFF RECURVATURE TRACK.  THERE IS LESS DIVERGENCE AMONG THE
VARIOUS COMPUTER MODELS NOW...ESPECIALLY THE GLOBAL MODELS...AND THE
GFDL AND GFDN MODELS ARE ALMOST IDENTICAL.  THE OFFICIAL FORECAST
TRACK IS CLOSE TO THE AVN/GFS MODEL AND A LITTLE TO THE TO THE LEFT
OF THE GFDL AND GFDN MODELS.
 
ALMA HAS LIKELY PEAKED OR IS VERY CLOSE TO IT...GIVEN THE CLOSE
PROXIMITY OF COLD AIR STRATOCUMULUS CLOUDS AND THE FACT THAT THE
CYCLONE IS NOW NEARING 26C SSTS. HOWEVER...THERE MAY BE ANOTHER
BRIEF BURST OF DEEP CONVECTION AND SOME SLIGHT STRENGTHENING DURING
THE NEXT 6 HOURS AS WE MOVE INTO THE DIURNAL CONVECTIVE MAXIMUM
PERIOD. OVERALL THOUGH...THE GENERAL TREND SHOULD BE FOR GRADUAL
WEAKENING TO OCCUR AS ALMA PASSES OVER SSTS AS LOW AS 24C BY 72
HOURS. THE SHIPS INTENSITY MODEL WAS FOLLOWED CLOSELY AND IT
INDICATES THAT THE VERTICAL SHEAR WILL DECREASE TO LESS THAN 10 KT
BY 48 HOURS...WHICH COULD HELP TO KEEP THE INTENSITIES A LITTLE
HIGHER THAN THE OFFICIAL FORECAST IS INDICATING.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     30/0300Z 14.9N 115.4W    90 KTS
12HR VT     30/1200Z 16.0N 115.4W    85 KTS
24HR VT     31/0000Z 17.2N 115.3W    75 KTS
36HR VT     31/1200Z 18.1N 115.2W    65 KTS
48HR VT     01/0000Z 18.8N 114.9W    55 KTS
72HR VT     02/0000Z 19.5N 114.0W    35 KTS
 
 
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