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TROPICAL STORM ALETTA DISCUSSION NUMBER  20
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT SAT MAY 27 2000
 
WERE IT NOT FOR MICROWAVE SSMI IMAGERY THE LOCATION OF ALETTA WOULD
BE A COMPLETE MYSTERY TONIGHT...HOWEVER...THE OVERPASS AT 0349Z
INDICATES THAT THE LOW-LEVEL CIRCULATION HAS BEEN DRIFTING TO THE
NORTHEAST OVERNIGHT AND HAS SEPARATED FROM THE MID-LEVEL CLOUD
PATTERN.  THERE IS NO LONGER ANY CONVECTION NEAR THE LOW-LEVEL
CENTER...AND IN FACT...ONLY THE DVORAK CONSTRAINTS ALLOW THE SYSTEM
TO BE CLASSIFIABLE.  THE INITIAL INTENSITY IS REDUCED TO 45 KT WITH
THIS ADVISORY.

THE TRACK GUIDANCE COVERS THE ENTIRE COMPASS...WITH THE STATISTICAL
P91E SHOWING A SOUTHEAST TRACK...THE SHALLOW BAM SOUTHWEST...THE
GFDL NORTHEAST...AND THE REMAINING MODELS...INCLUDING THE UKMET AND
NOGAPS...INDICATING A NORTHWEST TRACK.  THE GFDL SEEMS TO HAVE HAD
THE BEST HANDLE ON THIS SYSTEM OVER THE PAST DAY OR TWO...AND THE
OFFICIAL FORECAST IS ADJUSTED TOWARD THE GFDL AND IS TO THE RIGHT OF
THE PREVIOUS FORECAST.  LATER IN THE PERIOD THE FORECAST TRACK TURNS
BACK TO THE WEST-NORTHWEST.  THIS IS IN RESPONSE TO THE FORECAST
STRENGTHENING OF THE MID-TROPOSPHERIC RIDGE IN THE GLOBAL MODELS.

IN SPITE OF THE RAPID WEAKENING OF ALETTA TODAY...30 KT IN 24
HOURS...THE SHIPS INTENSITY FORECAST MODEL SHOWS ONLY MODEST
ADDITIONAL WEAKENING...AND IN FACT INDICATES SOME RESTRENGTHENING
LATE IN THE FORECAST PERIOD.  ONCE AGAIN...THE AVN SEEMS TO BE TOO
AGGRESSIVE WITH THE SPIN-UP OF THE SYSTEM BEHIND ALETTA...AND SO THE
DYNAMICAL INPUTS TO SHIPS MAY BE QUESTIONABLE.  THE OFFICIAL
INTENSITY FORECAST DOES NOT BUY THE REINTENSIFICATION...AND IF
ALETTA CANNOT REGENERATE ANY CONVECTION IT WILL DISSIPATE SOONER
RATHER THAN LATER. 
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     27/0900Z 15.3N 107.3W    45 KTS
12HR VT     27/1800Z 15.6N 107.0W    40 KTS
24HR VT     28/0600Z 16.1N 107.0W    35 KTS
36HR VT     28/1800Z 16.5N 107.3W    35 KTS
48HR VT     29/0600Z 17.0N 108.0W    35 KTS
72HR VT     30/0600Z 17.5N 109.5W    35 KTS
 
 
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