Tropical Depression LISA

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TROPICAL DEPRESSION LISA DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142010
500 AM AST THU SEP 23 2010
 
THE SATELLITE APPEARANCE OF LISA HAS CHANGED LITTLE DURING THE LAST
SEVERAL HOURS. BURSTS OF DEEP CONVECTION CONTINUE TO FORM PRIMARILY
NORTHEAST OF THE CIRCULATION CENTER BUT GENERALLY LACK MUCH
ORGANIZATION. THE CLOUD SHIELD ASSOCIATED WITH LISA HAS ALSO BECOME
MORE ASYMMETRIC DURING THE LAST 12 HOURS AND SEEMS PARTIALLY
INVOLVED WITH A SHARP MID- TO UPPER-LEVEL TROUGH LOCATED NORTHEAST
OF THE CYCLONE. DVORAK T-NUMBERS FROM SAB AND TAFB AT 0600 UTC HAVE
DECREASED TO 1.5 AND 2.5...RESPECTIVELY.  BASED UPON THESE
ESTIMATES AND DATA FROM AN EARLIER ASCAT PASS...THE INITIAL
INTENSITY IS LOWERED TO 30 KT. AS LISA ESCAPES THE INFLUENCE OF THE
NEARBY MID-LATITUDE TROUGH DURING THE NEXT DAY OR TWO...THE
STATISTICAL-DYNAMICAL GUIDANCE STILL INDICATES THE POTENTIAL FOR
SOME MINOR RE-INTENSIFICATION.  HOWEVER...WATERS ALONG THE FORECAST
TRACK ARE MARGINALLY WARM...THE OCEANIC HEAT CONTENT IS NOT
ESPECIALLY HIGH...AND THE CYCLONE SHOULD ENCOUNTER A SOMEWHAT
STABLE ENVIRONMENT.  BEYOND 48 HOURS...WESTERLY SHEAR ASSOCIATED
WITH A NEW UPPER-LEVEL TROUGH DIGGING TO THE NORTHWEST OF LISA IS
EXPECTED TO INCREASE SIGNIFICANTLY AND RESULT IN WEAKENING WHICH
COULD OCCUR FASTER THAN CURRENTLY FORECAST.  THE OFFICIAL NHC
INTENSITY FORECAST IS LOWERED TO ACCOUNT FOR CURRENT TRENDS AND IS
IN GOOD AGREEMENT WITH THE LATEST SHIPS/LGEM OUTPUT.
 
LISA HAS CONTINUED MOVING EASTWARD IN A WEAK WESTERLY STEERING
FLOW...AND THE INITIAL MOTION ESTIMATE IS 090/04.  AS THE MID- TO
UPPER-LEVEL TROUGH IMPARTING THIS MOTION LIFTS OUT DURING THE NEXT
12-24 HOURS...GLOBAL MODELS SHOW A LOW- TO MID-LEVEL RIDGE BUILDING
NORTH OF LISA WHICH SHOULD LEAD TO A GRADUAL NORTHWESTWARD TURN
WITH AN INCREASE IN FORWARD SPEED.  THE TRACK GUIDANCE HAS BEEN IN
REASONABLY GOOD AGREEMENT ON THIS SCENARIO...ALTHOUGH THE GFDL/
HWRF CONTINUE TO BE RIGHT OUTLIERS AS A RESULT OF WEAKER RIDGING.
THE NEW NHC TRACK FORECAST IS A BASICALLY AN UPDATE OF THE PREVIOUS
ONE AND IS LEFT OF THE MULTI-MODEL CONSENSUS...DOWNPLAYING THE
CONTRIBUTION OF THE GFDL/HWRF.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 17.7N  29.0W    30 KT
 12HR VT     23/1800Z 18.1N  29.0W    30 KT
 24HR VT     24/0600Z 18.5N  29.6W    35 KT
 36HR VT     24/1800Z 19.1N  30.3W    40 KT
 48HR VT     25/0600Z 20.0N  31.0W    40 KT
 72HR VT     26/0600Z 21.5N  32.5W    40 KT
 96HR VT     27/0600Z 23.5N  35.0W    35 KT
120HR VT     28/0600Z 26.0N  38.0W    25 KT...POST-TROP/REMNT LOW
 
$$
FORECASTER KIMBERLAIN
 
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