000
WTPZ44 KNHC 140836
TCDEP4
TROPICAL STORM CARLOS DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP042009
200 AM PDT TUE JUL 14 2009
 
CARLOS REMAINS A VERY SMALL TROPICAL CYCLONE CHARACTERIZED BY A
COMPACT BALL OF DEEP CONVECTION... BUT WITH A DISTINCT LACK OF
BANDING FEATURES.  THERE HAVE BEEN NO OBVIOUS STRUCTURAL CHANGES
DURING THE PAST SEVERAL HOURS...AND DVORAK T-NUMBERS OF 3.5 AND 4.0
FROM SAB AND TAFB...RESPECTIVELY...ARE ALSO LARGELY UNCHANGED. 
GIVEN CARLOS' QUASI-STEADY APPEARANCE...THE INITIAL INTENSITY IS
MAINTAINED AT 55 KT.

RECENT FIXES SUGGEST THAT CARLOS HAS BEEN MOVING 270/8...A LITTLE
SLOWER THAN BEFORE. THE NUMERICAL GUIDANCE HAS BEEN RATHER
INSISTENT ON CARLOS GAINING SOME LATITUDE...AND THE PRESENT CYCLE
OF MODEL RUNS IS NO DIFFERENT.  HOWEVER...PRELIMINARY VERIFICATION
OF PREVIOUS DYNAMICAL MODEL CONSENSUS FORECASTS REVEALS A
PRONOUNCED NORTHERLY BIAS.  ON THIS BASIS...THE NEW OFFICIAL
FORECAST FOLLOWS A SIMILAR PATH AS THE PREVIOUS AND KEEPS CARLOS
SOUTH OF THE GENERALLY MORE RELIABLE DYNAMICAL MODELS.  THIS IS
ALSO FAIRLY CLOSE TO THE BAM SUITE OF SOLUTIONS.  IN DEFERENCE TO
THE SLOWER INITIAL MOTION...HOWEVER...THIS NHC FORECAST IS SOMEWHAT
SLOWER THAN THE PREVIOUS ONE.  LATER IN THE FORECAST PERIOD...
CARLOS IS LIKELY TO BECOME EMBEDDED IN A FASTER LOW-LEVEL TRADE
WIND FLOW RESULTING IN SOME ACCELERATION.

GLOBAL MODELS INDICATE THAT CARLOS WILL BE ENTERING A REGION OF
INCREASING NORTHWESTERLY SHEAR DURING THE NEXT 24 TO 36 HOURS. 
EXPERIENCE HAS SHOWN THAT SMALL TROPICAL CYCLONE AT LOW LATITUDES
CAN BE VERY SUSCEPTIBLE TO EVEN MODEST INCREASES IN VERTICAL SHEAR. 
ALTHOUGH THE INTENSITY FORECAST CALLS FOR LITTLE CHANGE IN STRENGTH
FOLLOWED BY A GRADUAL DECREASE IN INTENSITY LATER IN THE FORECAST
PERIOD...CARLOS MAY WEAKEN FASTER THAN INDICATED HERE.  GIVEN THAT
THERE IS LITTLE SKILL IN INTENSITY PREDICTION...AND PERHAPS EVEN
LESS IN THIS CASE...THE CURRENT INTENSITY FORECAST REMAINS OF LOW
CONFIDENCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0900Z  9.7N 127.3W    55 KT
 12HR VT     14/1800Z  9.8N 128.6W    55 KT
 24HR VT     15/0600Z 10.0N 130.3W    55 KT
 36HR VT     15/1800Z 10.2N 132.4W    50 KT
 48HR VT     16/0600Z 10.4N 134.4W    45 KT
 72HR VT     17/0600Z 11.0N 139.0W    45 KT
 96HR VT     18/0600Z 11.5N 144.0W    40 KT
120HR VT     19/0600Z 11.5N 150.0W    40 KT
 
$$
FORECASTER KIMBERLAIN/PASCH