Hurricane LISA

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HURRICANE LISA DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142010
1100 PM AST FRI SEP 24 2010
 
RECENT SATELLITE IMAGES SHOW THAT THE EYE OF LISA HAS BECOME
OBSCURED BY CIRRUS CLOUDS.  HOWEVER...THE LATEST MICROWAVE PASS FROM
AROUND 2300 UTC STILL SHOWED THAT AN EYE WAS PRESENT. SATELLITE
ESTIMATES FROM TAFB AND SAB REMAIN 65 KT...THOUGH THE DATA-T VALUES
WERE HIGHER...AND THE ADT FROM UW-CIMSS WAS 72 KT. THE INITIAL
WINDS ARE SLIGHTLY INCREASED TO 70 KT AS A BLEND OF THESE DATA.
LISA BASICALLY HAS THE OVERNIGHT HOURS LEFT FOR ANY STRENGTHENING
UNTIL SOUTHWESTERLY SHEAR IS FORECAST BY ALL MODELS TO INCREASE. AS
THE CYCLONE MOVES FARTHER NORTH...IT SHOULD ALSO INGEST DRIER AIR
AND BE AFFECTED BY COOLER WATER TEMPERATURES. THUS STEADY WEAKENING
IS FORECAST TO BEGIN TOMORROW...AND THE NHC FORECAST IS CLOSE TO
THE SHIPS MODEL. SINCE LISA IS MUCH STRONGER THAN ANTICIPATED...
REMNANT LOW STATUS IS NOT FORECAST UNTIL DAY 4...THOUGH IT WOULD NOT
BE SURPRISING FOR IT TO HAPPEN SOONER DUE TO LISA REMAINING OVER
SUB-26C WATERS.
 
THE INITIAL MOTION CONTINUES TO BE 360/7.  THERE HAS BEEN A SUBTLE
SHIFT IN THE SYNOPTIC PATTERN FORECAST BY MOST OF THE MODELS DURING
THE PAST SEVERAL CYCLES.  A MID- TO UPPER-LEVEL TROUGH ALONG 35W IS
ADVANCING CLOSER TO THE TROPICAL CYCLONE THAN PREVIOUSLY EXPECTED.
CONSEQUENTLY...LESS RIDGING IS FORECAST TO BUILD TO THE NORTHEAST
OF THE CYCLONE...WHICH WOULD ALLOW A MORE NORTHWARD TRACK RATHER
THAN NORTHWESTWARD.  AS LONG AS LISA REMAINS A VERTICALLY STACKED
SYSTEM...A GENERAL MOTION TOWARD THE NORTH IS LIKELY...SIMILAR TO
THE GFS AND ITS DEPENDENT MODEL SUITE.  A NORTHWESTWARD TURN IS
POSSIBLE BY THE END OF THE FORECAST PERIOD...BUT THE SYSTEM WILL
EITHER BE A REMNANT LOW OR DISSIPATED BY THEN.  THE NHC FORECAST IS
SHIFTED TO THE RIGHT...AGAIN...BUT REMAINS TO THE WEST OF THE
DYNAMICAL MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/0300Z 20.7N  27.9W    70 KT
 12HR VT     25/1200Z 21.9N  28.1W    75 KT
 24HR VT     26/0000Z 23.7N  28.3W    65 KT
 36HR VT     26/1200Z 25.0N  28.5W    55 KT
 48HR VT     27/0000Z 26.4N  28.8W    45 KT
 72HR VT     28/0000Z 28.5N  29.2W    30 KT
 96HR VT     29/0000Z 30.5N  29.5W    25 KT...POST-TROP/REMNT LOW
120HR VT     30/0000Z...DISSIPATED
 
$$
FORECASTER BLAKE
 
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