000
WTNT44 KNHC 252032
TCDAT4
TROPICAL STORM LISA DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142010
500 PM AST SAT SEP 25 2010
 
CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE WESTERLY SHEAR
IS TAKING ITS TOLL ON LISA WITH ITS UPPER-LEVEL ANTICYCLONE NOW
DISPLACED MORE THAN 100 NMI TO THE EAST OF THE LOW-LEVEL CENTER. AS
A RESULT...SATELLITE INTENSITY ESTIMATES HAVE BEEN RAPIDLY
DECREASING DURING THE PAST 6 HOURS. THE INITIAL INTENSITY OF 45 KT
IS BASED ON A BLEND OF SATELLITE INTENSITY ESTIMATES T3.5/55 KT
FROM TAFB...T1.5/25 KT FROM SAB...AND AN ADT VALUE OF T3.0/45 KT
FROM UW-CIMSS.
 
THE INITIAL MOTION ESTIMATE IS 350/10. LISA REMAINS ON TRACK AND THE
CYCLONE IS EXPECTED TO TURN TOWARD THE NORTH-NORTHWEST DURING THE
NEXT 12 HOURS OR SO...AND CONTINUE THAT MOTION FOR THE REMAINDER OF
THE FORECAST PERIOD. THE NHC MODEL GUIDANCE IS MUCH MORE CONVERGENT
NOW...AND THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS
ADVISORY TRACK AND IS A LITTLE TO THE RIGHT OF THE MODEL CONSENSUS.
 
WESTERLY TO SOUTHWESTERLY VERTICAL SHEAR IS FORECAST TO INCREASE TO
MORE THAN 30 KT BY 24 HOURS...WHICH COULD HASTEN THE ONGOING
WEAKENING TREND. THE GFS-BASED SHIPS MODEL INDICATES DISSIPATION BY
48 HOURS...BUT THE OFFICIAL FORECAST DELAYS DISSIPATION DUE TO
INTERMITTENT BURSTS OF DEEP CONVECTION POSSIBLY KEEPING THE
CIRCULATION ALIVE A LITTLE BIT LONGER...WHICH IS SIMILAR TO THE
LGEM...HWRF...AND GFDL SOLUTIONS. THE OFFICIAL INTENSITY FORECAST
IS SIMILAR TO THE PREVIOUS ADVISORY AND IS A BLEND OF THE NHC
OBJECTIVE INTENSITY GUIDANCE.
 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/2100Z 23.7N  28.4W    45 KT
 12HR VT     26/0600Z 24.7N  28.6W    40 KT
 24HR VT     26/1800Z 26.1N  28.8W    35 KT
 36HR VT     27/0600Z 27.4N  29.0W    30 KT
 48HR VT     27/1800Z 28.6N  29.3W    30 KT
 72HR VT     28/1800Z 30.7N  30.0W    25 KT...POST-TROP/REMNT LOW
 96HR VT     29/1800Z 32.5N  30.5W    25 KT...POST-TROP/REMNT LOW
120HR VT     30/1800Z...DISSIPATED
 
$$
FORECASTER STEWART