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Tropical Depression LISA (Text)

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TROPICAL DEPRESSION LISA DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142010
1100 AM AST THU SEP 23 2010
 
VISIBLE AND INFRARED SATELLITE IMAGERY INDICATES DEEP CONVECTION HAS
INCREASED AND BECOME A LITTLE BETTER ORGANIZED NEAR THE CENTER OF
LISA. A 23/0907Z SSMIS MICROWAVE OVERPASS INDICATED A WELL-DEFINED
CURVED BAND OF CONVECTION HAD FORMED AND WRAPPED BETTER THAN HALF
WAY AROUND THE NORTH AND WEST SIDE OF THE CENTER. DVORAK SATELLITE
INTENSITY ESTIMATES ARE T2.0/30 KT FROM TAFB...T1.5/25 FROM SAB.
UW-CIMSS ADT ESTIMATE REMAIN WELL ABOVE THE SUBJECTIVE INTENSITY
ESTIMATES AT T3.3/51 KT. THE INITIAL INTENSITY FOR THIS ADVISORY
WILL BE HELD AT 30 KT...WHICH COULD BE A LITTLE LOW GIVEN THE RECENT
UPWARD TREND NOTED IN THE VARIOUS SATELLITE DATA.

LISA HAS BEEN DRIFTING EASTWARD...BUT A SLOW NORTHWARD MOTION OF
360/02 IS EXPECTED TO BEGIN WITHIN THE NEXT 6-12 HOURS. WATER VAPOR
IMAGERY INDICATES THE ELONGATED MID- TO UPPER-LEVEL TROUGH THAT HAS
BEEN NUDGING LISA EASTWARD THE PAST FEW DAYS IS BEGINNING TO SHOW
SIGNS OF SLOWLY LIFTING OUT TO THE NORTHEAST. THIS SHOULD ALLOW THE
WEAKNESS IN THE SUBTROPICAL RIDGE TO THE NORTH OF THE CYCLONE TO
FILL IN AND BEGIN TO STEER LISA TO THE NORTH AND EVENTUALLY
NORTHWESTWARD. THE LATEST MODEL GUIDANCE IS CONSISTENT WITH THIS
DEVELOPING SCENARIO AND SHOWS LESS SPREAD THAN PREVIOUS MODEL RUNS.
THE NHC FORECAST TRACK HAS BEEN SHIFTED A LITTLE TO THE RIGHT OF
THE PREVIOUS OF ADVISORY TRACK...BUT REMAINS ALONG THE EXTREME LEFT
SIDE OF THE MODEL GUIDANCE ENVELOPE.

NOW THAT THE AFOREMENTIONED UPPER-LEVEL TROUGH AND ITS ASSOCIATED
SOUTHWESTERLY ARE MOVING AWAY FROM LISA...THE UPPER-LEVEL OUTFLOW
PATTERN HAS IMPROVED. HOWEVER...THE NEARBY PRESENCE OF DRY
MID-LEVEL AIR REMAINS PROBLEMATIC IN THE INTENSITY FORECAST
PROCESS. THE LOWEST SHEAR AND BEST MOISTURE PROFILES FOR
INTENSIFICATION TO OCCUR ARE EXPECTED TO AFFECT LISA DURING THE
NEXT 24-36 HOURS. AFTER THAT...DRIER MID-LEVEL AIR...COOLER
SSTS...AND INCREASING WESTERLY SHEAR AHEAD OF ANOTHER
MID-TROPOSPHERIC TROUGH ARE EXPECTED TO INDUCE A STEADY WEAKENING
TREND. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
ADVISORY AND A BLEND OF NHC INTENSITY MODELS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/1500Z 17.5N  28.9W    30 KT
 12HR VT     24/0000Z 18.4N  29.2W    35 KT
 24HR VT     24/1200Z 19.2N  29.6W    35 KT
 36HR VT     25/0000Z 20.0N  30.3W    40 KT
 48HR VT     25/1200Z 20.8N  31.0W    40 KT
 72HR VT     26/1200Z 22.0N  32.2W    40 KT
 96HR VT     27/1200Z 24.2N  35.0W    35 KT
120HR VT     28/1200Z 26.5N  37.5W    25 KT...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 
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