Tropical Storm CARLOS

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TROPICAL STORM CARLOS DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP042009
200 AM PDT MON JUL 13 2009
 
CARLOS CONSISTS OF AN AMORPHOUS BLOB OF DEEP CONVECTION WITH A FEW
POORLY-DEFINED BANDING FEATURES OVER THE SOUTHERN AND WESTERN
PORTIONS OF THE CIRCULATION.  ITS RECENT APPEARANCE REPRESENTS A
DECREASE IN ORGANIZATION...AND SUBJECTIVE DVORAK T-NUMBERS OF 2.5
AND 3.0 FROM SAB AND TAFB...RESPECTIVELY...REFLECT A GRADUAL
WEAKENING.  THEREFORE THE INITIAL INTENSITY IS LOWERED TO 45
KT...WITHIN THE REALM OF AVAILABLE ESTIMATES.
 
THE WEAKENING OF CARLOS OBSERVED DURING THE PAST 24 HOURS HAS INDEED
BEEN PUZZLING...AND THUS THE INTENSITY FORECAST IS OF LOW
CONFIDENCE.  CARLOS HAS WELL-DEFINED UPPER-LEVEL OUTFLOW...AND IS
IN AN ENVIRONMENT OF LOW VERTICAL WIND SHEAR AND RELATIVELY WARM
SEA SURFACE TEMPERATURES.  ALL OF THESE FACTORS SHOULD FAVOR
INTENSIFICATION...YET THE CYCLONE HAS WEAKENED 30 KT SINCE THIS
TIME YESTERDAY.  THIS IS ANOTHER EXAMPLE OF OUR LACK OF
UNDERSTANDING OF TROPICAL CYCLONE INTENSITY CHANGE.  NO MATTER THE
INEXPLICABLE WEAKENING...THE GFDL AND GFDN MODELS PREDICT THAT
CARLOS WILL REACQUIRE HURRICANE STATUS...WHILE SHIPS INDICATES
LITTLE FURTHER DEVELOPMENT...AND THE HWRF WEAKENS CARLOS TO A
TROPICAL DEPRESSION.  GIVEN RECENT TRENDS AND THE LESS BULLISH
NUMERICAL GUIDANCE...THE OFFICIAL FORECAST WILL CALL FOR ONLY
MODEST STRENGTHENING EVEN THOUGH ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO REMAIN FAVORABLE FOR THE NEXT 2 TO 3 DAYS.
THEREAFTER...A SUBTLE INCREASE IN WESTERLY FLOW ALOFT AND SLIGHTLY
COOLER WATERS SHOULD RESULT IN WEAKENING.
 
THE INITIAL MOTION ESTIMATE IS 270/11.  THE NOGAPS AND GFDN MODELS
REMAIN NORTHERN OUTLIERS...AND ARE DISCOUNTED AS MOST DYNAMICAL
GUIDANCE INDICATES THE MID-LEVEL SUBTROPICAL RIDGE REMAINING
WELL-ESTABLISHED TO THE NORTH OF CARLOS THROUGH THE FORECAST
PERIOD.  ESSENTIALLY...THE NEW OFFICIAL FORECAST IS AN UPDATE OF
THE PREVIOUS ADVISORY BUT IS FARTHER SOUTH THAN THE MODEL
CONSENSUS...SINCE THE LATTER INCLUDES THE QUESTIONABLE NOGAPS AND
GFDN SOLUTIONS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0900Z 10.2N 124.1W    45 KT
 12HR VT     13/1800Z 10.2N 125.8W    50 KT
 24HR VT     14/0600Z 10.4N 128.0W    50 KT
 36HR VT     14/1800Z 10.7N 130.2W    55 KT
 48HR VT     15/0600Z 11.1N 132.3W    55 KT
 72HR VT     16/0600Z 11.9N 136.4W    55 KT
 96HR VT     17/0600Z 12.5N 141.0W    50 KT
120HR VT     18/0600Z 12.5N 145.5W    45 KT
 
$$
FORECASTER KIMBERLAIN/PASCH
 
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