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HURRICANE ALBERTO DISCUSSION NUMBER  17
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT TUE AUG 08 2000
 
ALBERTO HAS UNDERGONE SOUTHWESTERLY AND NOW SOUTHERLY SHEAR
OVERNIGHT WHICH HAS RESULTED IN SLIGHT WEAKENING AND THE CURRENT
INTENSITY IS DECREASED TO 70 KT. HOWEVER...THE UPPER-LEVEL OUTFLOW
REMAINS GOOD IN THE NORTHERN SEMICIRCLE.

INITIAL MOTION IS 285/13 OVER THE PAST 12 HOURS. HOWEVER...THE
MOTION IS CLOSER TO 275 DEGREES THE PAST 6 HOURS. ALBERTO HAS SHOWN
NO SIGNS OF BEING DEFLECTED POLEWARD BY THE LARGE UPPER-LEVEL TROUGH
SEEN IN WATER VAPOR IMAGERY...OR AS ADVERTISED BY MOST OF THE GLOBAL
MODELS. THE CURRENT POSITION IS MORE THAN 30 NM SOUTH OF THE UKMET
12Z POSITION AND AT LEAST 60 NM SOUTH OF THE FSU SUPERENSEMBLE 12Z
MODEL POSITION. THE 00Z AVIATION AND UKMET MODEL RUNS BUILD A 594 DM
500 MB HEIGHT CENTER DUE NORTH OF ALBERTO IN 24 HOURS WHICH SHOULD
PREVENT THE DEVELOPMENT OF ANY SIGNIFICANT POLEWARD MOTION. THE UW-
CIMMS WATER VAPOR WIND ANALYSES ALSO SHOW A LONG NORTHEAST OR EAST-
NORTHEAST FETCH OF 20 TO 30 KT WINDS FROM 850 TO 400 MB NORTH OF
ALBERTO. IT WOULD SEEM THAT THE MID- TO UPPER-LEVEL TROUGH HAS
BYPASSED ALBERTO...AND WE NOW FEEL THAT THE HURRICANE WILL STAY ON A
MORE WEST-NORTHWEST OR WESTERLY TRACK. WE ARE CLOSE TO THE PREVIOUS
FORECAST THROUGH 36 HOURS AND THEN TRACK ALBERTO OFF MORE WESTERLY
AFTERWARDS...WHICH IS A SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST
TRACKS. THIS IS SUPPORTED BY THE PAST 48 HOURS OF NOGAPS MODEL RUNS
WHICH HAVE HANDLED THE TRACK DIRECTION QUITE WELL...ALBEIT TOO SLOW.

IF ALBERTO SURVIVES THE SHEAR OVER THE NEXT 24 HOURS...THEN STEADY
INTENSIFICATION SHOULD RESUME AFTER THE CYCLONE PASSES WEST OF 50W
LONGITUDE WHERE IT WILL BE MOVING OVER 27C AND WARMER SSTS. IT IS
POSSIBLE THAT OUR INTENSITY FORECAST WILL BE TOO LOW AFTER 36 HOURS
WHEN ALBERTO WILL BE IN 200 MB SADDLE POINT...WHICH WOULD INDICATE
LOW/NO SHEAR AND FAVOR RAPID INTENSIFICATION.

FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     08/0900Z 17.1N  45.6W    70 KTS
12HR VT     08/1800Z 17.6N  47.5W    65 KTS
24HR VT     09/0600Z 18.5N  49.9W    65 KTS
36HR VT     09/1800Z 19.6N  52.4W    65 KTS
48HR VT     10/0600Z 21.0N  54.8W    70 KTS
72HR VT     11/0600Z 22.0N  60.0W    80 KTS
 
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