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HURRICANE ALETTA DISCUSSION NUMBER  11
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT WED MAY 24 2000
 
HURRICANE ALETTA HAS CONTINUED TO BECOME BETTER ORGANIZED AND HAS
RAPIDLY INTENSIFIED DURING THE PAST 6 HOURS. SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB ARE DVORAK T5.0 (90 KT) AND T4.5 (75
KT)...RESPECTIVELY. THE CDO HAS BECOME BETTER DEFINED WHILE TOPS
NEAR THE SYSTEM CENTER HAVE COOLED TO -85 TO -88C. THE EYE IS NO
LONGER APPARENT IN VISIBLE AND IR IMAGERY...BUT A 1649Z SSMI
OVERPASS CLEARLY INDICATED A WELL-DEFINED CLOSED EYEWALL SO WE HAVE
INCREASED THE INITIAL INTENSITY TO 80 KT.  OUTFLOW HAS IMPROVED TO
THE WEST BUT HAS BECOME SLIGHTLY RESTRICTED TO THE EAST DUE TO
INCREASING VERTICAL SHEAR. HOWEVER...THE SHIPS INTENSITY MODEL
CONTINUES STEADY INTENSIFICATION TO 95 KT THROUGH 36 HOURS WITH
GRADUAL AFTERWARDS AS ALETTA APPROACHES COOLER SSTS (26C) BY 72
HOURS. WE HAVE FOLLOWED SHIPS CLOSELY BUT HAVE HELD DOWN THE
INTENSITY SLIGHTLY DUE TO POSSIBLE ENTRAINMENT OF LOW-LEVEL STABLE
CLOUDS TO THE WEST AS INDICATED IN LATEST SATELLITE IMAGERY.
 
CURRENT MOTION IS 280/07 AND THERE REMAINS CONSIDERABLE DIVERGENCE
IN OUR FORECAST MODELS. THE GFDL HAS HAD A PERSISENT SHARP RIGHT OF
TRACK BIAS AND SLIGHT RECURVATURE FOR THE PAST 48 HOURS SO WE HAVE
DISCOUNTED THE LATEST GFDL SOLUTION. THE UKMET AND NOGAPS ARE
SIMILAR TO THE GFDL..ALBEIT TO A LESSER EXTENT...IN ALETTA GAINING
LATITUDE AFTER 12 TO 24 HOURS. THE NUMERICAL MODELS DO NOT APPEAR TO
BE HANDLING WELL THE 700 TO 200 MB HIGH PRESSURE RIDGE INDICATED IN
SYNOPTIC AND SATELLITE DATA CENTERED NEAR MANZANILLO AND EXTENDING
WESTWARD TO AT LEAST SOCORRO ISLAND. WITH SUCH DEEP MID- TO UPPER-
LEVEL STEERING FLOW...WE HAVE OPTED TO KEEP ALETTA ON A GENERAL SLOW
WESTWARD TRACK THROUGHOUT THE FORECAST PERIOD IN LINE WITH OUR
STATISTICAL-DYNAMICAL MODELS AND OUR PREVIOUS OFFICIAL FORECASTS. 
THE RADII OF 12 FT SEAS WERE INCREASED SIGNIFICANTLY BASED ON 18Z
SHIPS REPORTS.
 
FORECASTER STEWART/LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     25/0300Z 15.0N 107.2W    80 KTS
12HR VT     25/1200Z 15.3N 107.7W    85 KTS
24HR VT     26/0000Z 15.5N 108.4W    90 KTS
36HR VT     26/1200Z 15.6N 109.1W    90 KTS
48HR VT     27/0000Z 15.7N 109.7W    85 KTS
72HR VT     28/0000Z 15.7N 110.7W    75 KTS

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