000
WTPZ44 KNHC 241443
TCDEP4
TROPICAL STORM FRANK DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092010
800 AM PDT TUE AUG 24 2010
 
FRANK HAS MADE A RESURGENCE WITH A RING OF DEEP CONVECTION HAVING
DEVELOPED AROUND THE CIRCULATION CENTER DURING THE PAST 3 HOURS. A
24/0924Z TRMM MICROWAVE OVERPASS INDICATED TIGHTLY CURVED BANDS AND
THAT A 75 PERCENT EYEWALL HAD FORMED. SINCE THAT TIME...CONVECTION
IN INFRARED IMAGERY HAS IMPROVED SIGNIFICANTLY. A SATELLITE
INTENSITY ESTIMATE OF T3.5 OR 55 KT WAS ANALYZED BY BOTH TAFB AND
SAB...AND THAT IS THE INTENSITY USED FOR THIS ADVISORY.
 
MICROWAVE AND CONVENTIONAL SATELLITE FIXES SUGGEST A SLIGHTLY SLOWER
MOTION OF 285/06. THE TRACK FORECAST REASONING REMAINS UNCHANGED
OVER THE PAST 3 DAYS. THE STRONG SUBTROPICAL RIDGE TO THE NORTH OF
THE CYCLONE IS FORECAST TO KEEP FRANK MOVING IN A GENERAL
WEST-NORTHWESTWARD DIRECTION FOR THE NEXT 5 DAYS. A GRADUAL
DECREASE IN FORWARD SPEED IS EXPECTED BY DAYS 4 AND 5 DUE TO A
MID-LEVEL TROUGH FORECAST TO DIG SOUTHWARD OFF U.S. WEST COAST AND
BAJA CALIFORNIA...WHICH SHOULD WEAKEN THE WESTERN PERIPHERY OF THE
RIDGE AND DECREASE THE STEERING FLOW. THE LATEST GFDL RUN NOW TAKES
FRANK AND ITS WIND FIELD MUCH CLOSER TO THE SOUTHWESTERN COAST OF
MEXICO BY 36-48 HOURS. HOWEVER...GIVEN THE CURRENT AND FORECAST
STRENGTH AND LOCATION OF THE SUBTROPICAL RIDGE TO THE NORTH OF
FRANK...THE GFDL SOLUTION IS CONSIDERED AN OUTLIER AT THIS TIME.
THE OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE PREVIOUS
ADVISORY TRACK AND LIES BETWEEN THE CONSENSUS MODELS TVCN AND TVCC.

THE INTENSITY FORECAST IS A LITTLE TRICKY. ALTHOUGH THE GFS-BASED
SHIPS MODEL INDICATES NEAR 20 KT CURRENTLY ACROSS FRANK...THE
CYCLONE HAS STILL BECOME BETTER ORGANIZED. THE SHIPS AND LGEM
MODELS CONTINUE TO FORECAST SIMILAR SHEAR CONDITIONS ACROSS FRANK
FOR THE NEXT 24 HOURS OR SO. HOWEVER...UW-CIMSS SHEAR ANALYSES AND
WATER VAPOR WINDS SUGGEST THAT THE ACTUAL SHEAR OVER THE CENTER OF
FRANK IS CLOSER TO 15 KT. BY 36 HOURS...ALL OF THE DYNAMICAL AND
STATISTICAL INTENSITY MODELS ARE FORECASTING THE VERTICAL SHEAR TO
DECREASE TO AROUND 10 KT...WHICH WOULD PROVIDE A MORE FAVORABLE
ENVIRONMENT FOR INTENSIFICATION TO OCCUR. IN FACT...THE GFS AND
ECMWF MODELS ARE FORECASTING A SMALL UPPER-LEVEL ANTICYCLONE TO
DEVELOP OVER FRANK BY 48 HOURS. BASED ON THIS INFORMATION...FRANK
COULD BECOME A HURRICANE IN THE NEXT 24 HOURS. BY DAYS 4 AND 5...
THE CYCLONE IS EXPECTED TO BE MOVING OVER SUB-26C SSTS...WHICH
SHOULD INDUCE GRADUAL WEAKENING. THE OFFICIAL INTENSITY FORECAST IS
SIMILAR TO THE SHIPS AND LGEM INTENSITY MODELS...AND HIGHER THAN
THE GFDL AND HWRF MODELS.
 
SINCE THE FORECAST TRACK KEEPS FRANK WELL OFFSHORE OF THE COAST OF
MEXICO...ALL WATCHES AND WARNINGS FOR MEXICO WERE DISCONTINUED
EARLIER THIS MORNING.
 
HEAVY RAINS WILL BE POSSIBLE OVER PORTIONS OF SOUTHERN MEXICO
AND CENTRAL AMERICA DURING THE NEXT DAY OR TWO.  ALTHOUGH THESE
RAINS ARE NOT DIRECTLY ASSOCIATED WITH FRANK...THEY STILL POSE A
SERIOUS FLOOD THREAT.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      24/1500Z 15.4N 101.4W    55 KT
 12HR VT     25/0000Z 15.8N 102.7W    60 KT
 24HR VT     25/1200Z 16.5N 104.4W    65 KT
 36HR VT     26/0000Z 17.2N 106.0W    65 KT
 48HR VT     26/1200Z 17.9N 107.6W    70 KT
 72HR VT     27/1200Z 19.1N 110.5W    70 KT
 96HR VT     28/1200Z 20.0N 112.5W    65 KT
120HR VT     29/1200Z 21.0N 113.5W    55 KT
 
$$
FORECASTER STEWART