Tropical Storm DARBY

ZCZC MIATCDEP5 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM DARBY DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP052010
200 PM PDT WED JUN 23 2010
 
CONVECTIVE BANDING HAS CONTINUED TO INCREASE MARKEDLY AND A BANDING
EYE HAS OCCASIONALLY BEEN EVIDENT IN BOTH VISIBLE AND MICROWAVE
IMAGERY. UPPER-LEVEL OUTFLOW HAS ALSO BEEN IMPROVING...ESPECIALLY
IN THE WESTERN SEMICIRCLE. THE INITIAL INTENSITY IS INCREASED TO 
55 KT BASED ON AN INTENSITY ESTIMATE OF T3.5/55 KT FROM SAB.
 
THE INITIAL MOTION ESTIMATE IS 285/10. THERE IS NO CHANGE TO THE
PREVIOUS FORECAST REASONING. THE FUTURE TRACK OF DARBY CONTINUES TO
WEIGH HEAVILY UPON THE DEVELOPMENT OF A DISTURBANCE LOCATED OVER
THE WEST-CENTRAL CARIBBEAN SEA. THE MAJORITY OF THE MODELS...
ESPECIALLY THE ECMWF...CONTINUE TO DEVELOP THE CARIBBEAN SEA
DISTURBANCE TO VARIOUS DEGREES OVER THE NEXT 5 DAYS AND MOVE THAT
SYSTEM INTO THE SOUTHERN GULF OF MEXICO. THIS RESULTS IN WEAKENING
OF THE SUBTROPICAL RIDGE TO THE NORTH OF DARBY BY 96-120 HOURS AND
CAUSES A DECREASE IN THE STEERING FLOW. BOTH THE GFS AND
GFS-PARALLEL RUNS TAKE A RATHER ANEMIC LOOKING DARBY QUICKLY
WESTWARD...WHICH ONCE AGAIN APPEARS TO BE DUE TO POOR MODEL
INITIALIZATION. AS A RESULT...LESS WEIGHT HAS BEEN PLACED ON THOSE
MODELS...WITH MORE WEIGHT BEING PLACED ON THE ECMWF...NOGAPS...
UKMET...AND CANADIAN MODELS.
 
DARBY APPEARS TO ALREADY BE ABOUT 12 HOURS INTO A RAPID
INTENSIFICATION PHASE. THIS TREND IS FORECAST TO CONTINUE FOR
ANOTHER 12 HOURS OR SO WITH SLOWER DEVELOPMENT AFTER THAT. A
23/1606Z TRMM OVERPASS INDICATED THAT THE EARLIER OBSERVED SLIGHT
WESTWARD TILT OF THE INNER CORE VORTEX COLUMN HAD DIMINISHED...
WHICH WOULD INDICATE THAT DARBY HAS BETTER VERTICAL STRUCTURE THAT
IS CONDUCIVE FOR CONTINUED STRENGTHENING. THE SHIPS MODEL SHOWS
LESS THAN 5 KT OF VERTICAL SHEAR THROUGH 48 HOURS...WHICH WOULD
ALSO SUPPORT CONTINUED STRENGTHENING...AND IT IS QUITE POSSIBLE
THAT DARBY COULD BE A MAJOR HURRICANE BY THAT TIME. BY 96 HOURS...
THE VERTICAL SHEAR IS EXPECTED TO INCREASE...BUT MUCH LESS NOW THAN
PREVIOUS EXPECTED. THE OFFICIAL INTENSITY FORECAST IS HIGHER THAN
THE PREVIOUS ADVISORY AND IS BASED ON A BLEND OF THE SHIPS AND LGEM
INTENSITY MODELS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/2100Z 12.0N  96.1W    55 KT
 12HR VT     24/0600Z 12.3N  97.2W    70 KT
 24HR VT     24/1800Z 12.7N  98.8W    80 KT
 36HR VT     25/0600Z 13.0N 100.0W    85 KT
 48HR VT     25/1800Z 13.4N 101.0W    90 KT
 72HR VT     26/1800Z 14.0N 102.0W    90 KT
 96HR VT     27/1800Z 14.5N 102.1W    90 KT
120HR VT     28/1800Z 15.0N 102.1W    75 KT
 
$$
FORECASTER STEWART
 
NNNN