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TROPICAL STORM ALETTA DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT TUE MAY 23 2000

THERE HAS BEEN A GRADUAL INCREASE IN ORGANIZATION OF THE TROPICAL
CYCLONE...WITH ENOUGH BANDING FEATURES ON THE SATELLITE IMAGES TO
YIELD A DATA T-NUMBER OF 2.5 ON THE DVORAK SCALE.  THIS EQUATES TO
MINIMAL STORM STRENGTH...SO THE SYSTEM IS BEING NAMED.  HIGH CLOUD
MOTIONS SHOW FAIR UPPER-LEVEL ANTICYCLONIC OUTFLOW TO THE WEST AND
NORTH OF THE STORM.  SEA SURFACE TEMPERATURES AND VERTICAL SHEAR
FAVOR SLOW STRENGTHENING FOR THE NEXT COUPLE OF DAYS. LATE IN THE
FORECAST PERIOD...VERTICAL SHEAR MAY BECOME LESS FAVORABLE AND WATER
TEMPERATURES SHOULD COOL SLIGHTLY.

LATEST CENTER FIXES INDICATE SOME SLOWING OF THE FORWARD SPEED AND
CURRENT MOTION ESTIMATE IS 295/09.  A LARGE MID-TROPOSPHERIC CYCLONE
TO THE WEST OF BAJA IS EXPECTED TO MOVE SLOWLY NORTHEASTWARD DURING
THE FORECAST PERIOD.  HOWEVER THIS FEATURE SHOULD ERODE THE RIDGE TO
THE NORTH AND NORTHWEST OF ALETTA TO SOME EXTENT...SO STEERING
CURRENTS ARE LIKELY TO WEAKEN FURTHER.  THEREFORE THE OFFICIAL
FORECAST...WHICH IS SIMILAR TO THE PREVIOUS ONE...SHOWS A CONTINUED
DECREASE IN FORWARD SPEED.     
 
THERE IS STILL A RISK OF LOCALLY HEAVY RAINFALL OVER PORTIONS OF
SOUTHERN MEXICO DURING THE NEXT DAY OR SO...FROM OUTER BANDS
ASSOCIATED WITH THE TROPICAL STORM.

PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     23/0900Z 14.8N 102.1W    35 KTS
12HR VT     23/1800Z 15.4N 103.4W    40 KTS
24HR VT     24/0600Z 16.1N 105.0W    50 KTS
36HR VT     24/1800Z 16.6N 106.3W    55 KTS
48HR VT     25/0600Z 17.0N 107.5W    60 KTS
72HR VT     26/0600Z 17.5N 109.5W    60 KTS
 
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