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HURRICANE BEATRIZ DISCUSSION NUMBER  18
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT TUE JUL 13 1999

BEATRIZ REMAINS WELL-ORGANIZED WITH A WELL-DEFINED 20 N MI DIAMETER
EYE AND OBJECTIVE T-NUMBERS OF 5.6-5.7. DVORAK INTENSITY ESTIMATES
FROM TAFB...SAB...AND AFWA REMAIN AT T5.5...102 KT...THUS THE
INITIAL INTENSITY REMAINS 105 KT.

THE HURRICANE HAS TURNED WEST-NORTHWEST OVER THE PAST 12 HOURS WITH
A MOTION OF 290/10. THE REASON FOR THE TURN IS NOT OBVIOUS.
HOWEVER... AN UPPER LEVEL LOW APPARENT IN WATER VAPOR IMAGERY NEAR
22N119W MAY BE WEAKENING THE RIDGE NORTH OF BEATRIZ. THE 06Z
AVIATION MODEL DEVELOPS A ELONGATED CYCLONIC VORTEX FROM BEATRIZ AND
THE TROPICAL DISTURBANCE NEAR THE MEXICAN COAST. THIS CAUSES THE
MODEL TO MOVE THE STORM IN A HALF-LOOP...WHICH APPEARS UNLIKELY
GIVEN THE CURRENT TRENDS. THE BAM MODELS ARE ALSO AFFECTED BY THE
VORTEX...TURNING BEATRIZ WEST-SOUTHWEST AFTER 36 HOURS. THE NOGAPS
AND GDFL KEEP CALLING FOR A NORTHWEST TRACK TO THE RIGHT OF THE
OTHER GUIDANCE. THE OFFICIAL FORECAST MAINTAINS BEATRIZ ALONG A
WEST-NORTHWESTWARD TRACK...WITH SOME SLOWING AFTER 36 HOURS AS A
TROUGH NEAR THE U.S. WEST COAST WEAKENS THE RIDGE. THIS IS IN
REASONABLE AGREEMENT WITH THE LBAR AND UKMET...AND IS SHIFTED TO THE
NORTH OF THE PREVIOUS FORECAST.

THE MORE NORTHERLY TRACK SHOULD BRING BEATRIZ TO COLDER WATER MORE
QUICKLY THAN THE PREVIOUS FORECAST...WHICH SHOULD ALLOW A FASTER
WEAKENING. THE INTENSITY FORECAST CALLS FOR BEATRIZ TO WEAKEN
BELOW HURRICANE STRENGTH BETWEEN 48 AND 72 HOURS.

TROPICAL-STORM FORCE WIND RADII HAVE BEEN EXPANDED BASED ON A 12Z
REPORT FROM SHIP VRUM4...WHICH HAD 35 KT WINDS 190 N MI NORTH-
NORTHEAST OF THE CENTER.
 
BEVEN/AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     13/1500Z 15.3N 122.7W   105 KTS
12HR VT     14/0000Z 15.8N 124.2W   100 KTS
24HR VT     14/1200Z 16.4N 126.1W    90 KTS
36HR VT     15/0000Z 17.3N 128.0W    80 KTS
48HR VT     15/1200Z 18.0N 129.5W    70 KTS
72HR VT     16/1200Z 19.0N 131.5W    50 KTS
 
 
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