000
WTPZ44 KNHC 230256
TCDEP4
TROPICAL STORM FRANK DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092010
800 PM PDT SUN AUG 22 2010
 
THE OVERALL ORGANIZATION OF FRANK HAS CHANGED LITTLE THIS EVENING.
THUNDERSTORMS OVER THE NORTHWESTERN QUADRANT OF THE CYCLONE HAVE
WEAKENED WHILE INCREASED BANDING IS OCCURRING TO THE SOUTH AND
SOUTHEAST OF THE CENTER. THE INITIAL INTENSITY WILL REMAIN 50
KT...WHICH IS A BLEND OF SATELLITE ESTIMATES OF 45 KT AND 55 KT
FROM SAB AND TAFB RESPECTIVELY.
 
RECENT FIXES FROM CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY SHOW
THAT FRANK IS MOVING WESTWARD AT ABOUT 6 KT.  THE CYCLONE IS
FORECAST TO CONTINUE MOVING WEST TO WEST-NORTHWEST TO THE SOUTH OF
A DEEP-LAYER RIDGE OVER WESTERN NORTH AMERICA.  MOST OF THE TRACK
MODELS AGREE ON THIS SCENARIO...BUT THERE REMAINS LARGE SPREAD IN
THE FORECAST FORWARD SPEED OF FRANK.  THE GFS AND ECMWF ARE MUCH
SLOWER THAN THE GFDL AND HWRF MODELS...ESPECIALLY DURING THE FIRST
48 HOURS.  THE SYNOPTIC PATTERN TENDS TO FAVOR AT LEAST A STEADY
WEST-NORTHWESTWARD MOTION AND THE OFFICIAL FORECAST IS THEREFORE
FASTER THAN THE GFS/ECMWF...BUT NOT QUITE AS FAST AS THE REGIONAL
HURRICANE MODELS.  GIVEN THE LARGE UNCERTAINLY AT 72 HOURS AND
BEYOND...THE OFFICIAL FORECAST WILL REMAIN CLOSE TO THE TVCN
CONSENSUS AT THOSE FORECAST TIMES.
 
ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR SOME STRENGTHENING
DURING THE NEXT DAY OR SO.  DESPITE SHOWING AN INCREASE IN EASTERLY
SHEAR IN 12 TO 24 HOURS...THE SHIPS/LGEM MODELS BRING FRANK TO
HURRICANE STRENGTH WITHIN TWO DAYS. THE GFDL/HWRF MODELS SHOW A
LITTLE LESS INTENSIFICATION THAN THEY DID BEFORE.  THE UPDATED
FORECAST REMAINS CLOSER TO THE STATISTICAL GUIDANCE AND IS
UNCHANGED FROM THE PREVIOUS NHC ADVISORY.
 
GIVEN THE NEW FORECAST TRACK...THE GOVERNMENT OF MEXICO HAS EXTENDED
THE TROPICAL STORM WARNING AND WATCH WESTWARD ALONG THE COAST OF
SOUTHERN MEXICO.


FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0300Z 14.0N  96.8W    50 KT
 12HR VT     23/1200Z 14.2N  97.8W    60 KT
 24HR VT     24/0000Z 14.6N  99.5W    65 KT
 36HR VT     24/1200Z 15.2N 101.0W    70 KT
 48HR VT     25/0000Z 15.7N 102.2W    75 KT
 72HR VT     26/0000Z 16.7N 104.6W    75 KT
 96HR VT     27/0000Z 17.7N 107.0W    70 KT
120HR VT     28/0000Z 18.5N 110.0W    70 KT
 
$$
FORECASTER BROWN