Tropical Storm FRANK

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TROPICAL STORM FRANK DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092010
800 AM PDT SUN AUG 22 2010
 
THE CLOUD PATTERN ASSOCIATED WITH THE CYCLONE HAS CONTINUED TO
BECOME BETTER ORGANIZED...AND 1200 UTC DVORAK ESTIMATES WERE 2.5
FROM SAB AND 3.0 FROM TAFB.  BASED ON A BLEND OF THE SATELLITE
ESTIMATES...THE DEPRESSION IS UPGRADED TO A TROPICAL STORM AND THE
INITIAL INTENSITY IS SET AT 40 KNOTS.  THE SHIPS MODEL AND UW-CIMSS
SATELLITE ANALYSIS SHOW THAT FRANK IS LOCATED IN A LOW SHEAR
ENVIRONMENT.  THIS...COMBINED WITH WARM WATERS AND A VERY MOIST
LOWER TO MID-TROPOSPHERE SUGGEST THAT STRENGTHENING IS LIKELY.
HOWEVER...THE SHIPS MODEL SHOWS THE SHEAR INCREASING TO 15 TO 20
KNOTS IN THE NEXT 12 TO 24 HOURS...WHICH COULD TEMPER
INTENSIFICATION SOMEWHAT.  THE OFFICIAL FORECAST IS ADJUSTED UPWARD
THROUGH THE FIRST 48 HOURS AND IS CLOSE TO A BLEND OF THE SHIPS AND
LGEM THROUGH THE PERIOD.
 
AN 0804 UTC AMSR-E PASS AND 1201 UTC SSM/I PASS WERE HELPFUL IN
LOCATING THE CENTER...WHICH IS LOCATED A LITTLE FARTHER NORTH AND
WEST THAN PREVIOUSLY ESTIMATED.  THE INITIAL MOTION ESTIMATE IS
270/6...AS THE CYCLONE IS BEING STEERED BY A DEEP-LAYER RIDGE
CENTERED OVER THE SOUTHWESTERN UNITED STATES.  ALL OF THE GLOBAL
MODEL AND ENSEMBLE GUIDANCE IS IN GOOD AGREEMENT SHOWING THE CORE
OF THE RIDGE SHIFTING NORTHWESTWARD DURING THE FORECAST PERIOD...
AND THIS SHOULD ALLOW FRANK TO TURN GRADUALLY TOWARD THE
WEST-NORTHWEST WITHIN A DAY OR SO...AND REMAIN ON THAT HEADING
THROUGH THE FORECAST PERIOD.  WHILE MOST OF THE TRACK MODEL
GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO...THERE REMAINS
CONSIDERABLE DISAGREEMENT ON HOW CLOSE FRANK WILL GET TO THE COAST
OF MEXICO.  THE OFFICIAL FORECAST HAS BEEN ADJUSTED NORTHWARD
TOWARD THE TVCN MULTI-MODEL CONSENSUS...AND IS FASTER THAN THE
PREVIOUS PACKAGE. 
 
GIVEN THE ADJUSTMENTS TO THE TRACK FORECAST...A TROPICAL STORM
WARNING IS NOW NEEDED FOR PORTIONS OF THE MEXICAN COAST.  BASED ON
THE OFFICIAL FORECAST AND PREVIOUS NHC FORECAST ERRORS...THERE IS
ABOUT A 20 TO 35 PERCENT CHANCE OF TROPICAL STORM FORCE WINDS
AFFECTING ANY INDIVIDUAL POINT LOCATION WITHIN THE WARNING
AREA. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/1500Z 14.0N  95.3W    40 KT
 12HR VT     23/0000Z 14.1N  96.3W    50 KT
 24HR VT     23/1200Z 14.2N  97.8W    60 KT
 36HR VT     24/0000Z 14.6N  99.3W    65 KT
 48HR VT     24/1200Z 15.1N 100.8W    65 KT
 72HR VT     25/1200Z 16.5N 103.5W    70 KT
 96HR VT     26/1200Z 17.5N 106.0W    70 KT
120HR VT     27/1200Z 18.5N 109.0W    70 KT
 
$$
FORECASTER BRENNAN
 
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