Hurricane FRANK

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HURRICANE FRANK DISCUSSION NUMBER  24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092010
800 AM PDT FRI AUG 27 2010
 
FRANK CONTINUES TO WEAKEN.  THE CLOUD PATTERN CONSISTS OF A SMALL
AREA OF PULSATING DEEP CONVECTION JUST TO THE WEST OF THE ESTIMATED
CENTER...WITH VERY LITTLE IN THE WAY OF BANDING FEATURES.  DVORAK
T-NUMBERS FROM SAB AND TAFB ARE 3.5 AND 4.5 RESPECTIVELY.  ALTHOUGH
THE DVORAK RULES SPECIFY 77 KT FOR THE CURRENT INTENSITY...THESE
RULES HAVE BEEN KNOWN TO YIELD A HIGH BIAS FOR WEAKENING TROPICAL
CYCLONES.  USING A BLEND OF T-NUMBERS AND CURRENT INTENSITY
VALUES...THE WIND SPEED IS SET TO 65 KT FOR THIS ADVISORY.  WITH
THE CYCLONE MOVING ACROSS A GRADIENT OF DECREASING SEA SURFACE
TEMPERATURES...STEADY WEAKENING IS PREDICTED.  THE OFFICIAL
INTENSITY FORECAST FOLLOWS THE STATISTICAL/DYNAMICAL LGEM GUIDANCE
RATHER CLOSELY.  FRANK IS PREDICTED TO DROP BELOW TROPICAL STORM
STRENGTH IN ABOUT 48 HOURS...HOWEVER THIS EVENT COULD EASILY OCCUR
SOONER.
 
FIRST-LIGHT VISIBLE IMAGES SHOW THAT THE CENTER OF FRANK HAS NOT
MOVED AS FAR TO THE WEST-NORTHWEST AS EARLIER ESTIMATED...AND THIS
REQUIRES A SLIGHT EASTWARD RELOCATION FOR THIS PACKAGE.  BASED ON
THE ADJUSTMENTS TO THE TRACK...THE FORWARD MOTION IS ESTIMATED TO
HAVE SLOWED TO NEAR 5 KT.  EVEN FURTHER DECELERATION IS LIKELY AS
THE MID-LEVEL RIDGE TO THE NORTH OF FRANK CONTINUES TO BREAK DOWN
DUE TO A DIGGING 500 MB TROUGH OVER CALIFORNIA.  SINCE THE SYSTEM
SHOULD BE REDUCED TO A SHALLOW CYCLONE IN 2-3 DAYS... IT WILL
PROBABLY NOT RESPOND MUCH TO THE STEERING FLOW ASSOCIATED WITH THE
ABOVE MENTIONED TROUGH.  THEREFORE...THE OFFICIAL TRACK FORECAST
SLOWS THE FORWARD SPEED TO A CRAWL LATER IN THE FORECAST PERIOD.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/1500Z 18.8N 112.0W    65 KT
 12HR VT     28/0000Z 19.3N 112.7W    55 KT
 24HR VT     28/1200Z 20.0N 113.6W    45 KT
 36HR VT     29/0000Z 20.8N 114.0W    40 KT
 48HR VT     29/1200Z 21.2N 114.0W    35 KT
 72HR VT     30/1200Z 22.0N 114.0W    30 KT
 96HR VT     31/1200Z 22.5N 114.0W    25 KT...POST-TROP/REMNT LOW
120HR VT     01/1200Z 23.0N 114.0W    20 KT...POST-TROP/REMNT LOW
 
$$
FORECASTER PASCH
 
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