Tropical Storm LISA

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TROPICAL STORM LISA DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142010
500 PM AST WED SEP 22 2010
 
LISA HAS A ROBUST CIRCULATION...BUT ALL THE DEEP CONVECTION REMAINS
LIMITED TO NEAR THE CENTER.  THE CONVECTIVE STRUCTURE HAS CHANGED
LITTLE OVER THE PAST FEW HOUR HOURS...SO THE INITIAL INTENSITY IS
KEPT AT 40 KT.  ALTHOUGH VERTICAL SHEAR IS LIGHT...THE CYCLONE IS
SURROUNDED BY MID-LEVEL DRY AIR AND IS LOCATED OVER AN AREA WHERE
THE OCEAN HEAT CONTENT IS RATHER LOW.  THEREFORE ONLY A LITTLE
STRENGTHENING IS INDICATED IN THE OFFICIAL FORECAST DURING THE NEXT
48 HOURS...WHEN CONDITIONS WILL BE MOST FAVORABLE.  WEAKENING IS
EXPECTED FROM DAYS 3-5 AS 30-40 KT OF WEST-SOUTHWESTERLY SHEAR
DEVELOPS OVER THE CYCLONE.  THE FORECAST INDICATES LISA BECOMING A
TROPICAL DEPRESSION BY DAY 5...BUT IT IS POSSIBLE THAT IT COULD
HAVE DEGENERATED TO A REMNANT LOW OR TROUGH BY THAT TIME.
 
LISA HAS BEEN MEANDERING ALL DAY...AND THE ESTIMATED INITIAL MOTION
IS 090/3 BASED ON A 12-18 HOUR AVERAGE.  MODEL GUIDANCE SUGGESTS
THAT LISA COULD DRIFT A LITTLE FARTHER EASTWARD OR SOUTHEASTWARD
DURING THE NEXT 12-24 HOURS IN WEAK STEERING FLOW...BUT IT IS
EXPECTED TO PICK UP SOME SPEED AND MOVE NORTHWESTWARD BY 48 HOURS
AS A MID-LEVEL RIDGE OVER AFRICA BUILDS WESTWARD.  THE TRACK
GUIDANCE HAS SHIFTED TO THE NORTH...AND THE OFFICIAL FORECAST IS
ABOUT 2 DEGREES FARTHER NORTH THAN THE PREVIOUS ONE BY DAY 5.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/2100Z 17.7N  30.2W    40 KT
 12HR VT     23/0600Z 17.6N  29.9W    40 KT
 24HR VT     23/1800Z 17.8N  29.9W    45 KT
 36HR VT     24/0600Z 18.1N  30.6W    45 KT
 48HR VT     24/1800Z 18.6N  31.2W    50 KT
 72HR VT     25/1800Z 20.1N  32.7W    45 KT
 96HR VT     26/1800Z 22.0N  35.0W    40 KT
120HR VT     27/1800Z 24.0N  38.0W    30 KT
 
$$
FORECASTER BERG
 
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