Tropical Storm CARLOS

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TROPICAL STORM CARLOS DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP042009
800 PM PDT WED JUL 15 2009
 
WESTERLY VERTICAL WIND SHEAR CONTINUES TO AFFECT CARLOS...WITH
OCCASIONAL PUFFS OF CONVECTION OCCURRING JUST EAST OF THE CENTER. 
THERE IS ALSO SOME POORLY-DEFINED OUTER BANDING IN THE SOUTHEASTERN
SEMICIRCLE.  WHILE SATELLITE INTENSITY ESTIMATES FROM SAB AND TAFB
REMAIN 55 KT...THE RAGGED APPEARANCE OF CARLOS SUGGESTS IT HAS
WEAKENED SINCE 18Z.  THE INITIAL INTENSITY IS REDUCED TO A SOMEWHAT
UNCERTAIN 45 KT.

THE INITIAL MOTION IS NOW 275/11.  OTHER THAN THAT...THERE IS LITTLE
CHANGE IN THE FORECAST GUIDANCE OR REASONING SINCE THE LAST
PACKAGE.  CARLOS IS IN EASTERLY FLOW SOUTH OF A LOW/MID-LEVEL
RIDGE...AND BY 36 HR IS FORECAST TO BE UNDER NORTHERLY TO
NORTHEASTERLY UPPER-LEVEL FLOW.  THIS PATTERN SUGGESTS THAT THERE
IS LITTLE REASON FOR CARLOS TO GAIN MUCH LATITUDE...ESPECIALLY AS
MUCH AS FORECAST BY THE RIGHT-OUTLIERS NOGAPS AND GFDN.  THE NEW
FORECAST TRACK IS SIMILAR TO THE PREVIOUS FORECAST...AND IT IS IN
BEST AGREEMENT WITH THE BAMM...BAMD...AND GFS MODELS.

THE INTENSITY FORECAST IS PROBLEMATIC.  CARLOS IS EXPECTED TO REMAIN
IN 15-20 KT OF SHEAR FOR THE NEXT COUPLE OF DAYS...WITH THE SHEAR
DIRECTION LIKELY TO CHANGE FROM WESTERLY TO NORTHERLY DURING THAT
TIME.  THIS IS ENOUGH SHEAR TO HAVE AN IMPACT ON A CYCLONE AS SMALL
AS CARLOS.  THE HWRF FORECASTS THE CYCLONE TO DISSIPATE AFTER 72
HR...WHILE THE OTHER INTENSITY GUIDANCE HOLDS ON TO IT THROUGH
120 HR.  BASED ON THIS...THE INTENSITY FORECAST CALLS FOR CARLOS TO
CONTINUE TO WEAKEN FOR 24-36 HR AND THEN PERSIST THROUGH 120 HR IN
BEST AGREEMENT WITH THE LGEM MODEL.   ALTERNATE SCENARIOS ARE THAT
THE SMALL CIRCULATION DECAYS TO A TROUGH...OR THAT IT GETS ABSORBED
BY A LARGER ITCZ DISTURBANCE TO THE SOUTHWEST.  EITHER OF THESE
COULD HAPPEN IN THE NEXT DAY OR TWO.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0300Z 10.2N 132.0W    45 KT
 12HR VT     16/1200Z 10.3N 133.5W    35 KT
 24HR VT     17/0000Z 10.3N 135.6W    30 KT
 36HR VT     17/1200Z 10.3N 137.8W    30 KT
 48HR VT     18/0000Z 10.4N 140.4W    30 KT
 72HR VT     19/0000Z 10.5N 146.0W    30 KT
 96HR VT     20/0000Z 10.0N 152.0W    25 KT
120HR VT     21/0000Z 10.0N 158.0W    25 KT
 
$$
FORECASTER BEVEN
 
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