Tropical Storm OTTO

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TROPICAL STORM OTTO DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 AM AST THU OCT 07 2010
 
OTTO HAS FINALLY TRANSITIONED INTO A TROPICAL CYCLONE BASED ON A
07/0935Z AMSU VERTICAL TEMPERATURE ANALYSIS PROFILE FROM UW-CIMSS
THAT INDICATED THE WARM CORE HAD MOVED UPWARD FROM THE MID-LEVELS
TO THE UPPER-LEVELS OF THE CYCLONE. A RECENT BURST OF DEEP
CONVECTION WITH CLOUD TOP TEMPERATURES NEAR -80C THAT HAS DEVELOPED
OVER THE CENTER ALSO SUPPORTS A TRANSITION TO TROPICAL CYCLONE
STATUS. SATELLITE INTENSITY ESTIMATES ARE RUNNING BETWEEN T2.0/30
KT AND T2.5/35 KT FROM TAFB...SAB...AND UW-CIMSS USING A CURVED
BAND PATTERN. HOWEVER...USING A SHEAR PATTERN WITH THE RECENT BURST
OF CENTRAL CONVECTION YIELDS A VALUE OF T3.5/55 KT. SINCE THE
CONVECTION HAS ONLY PERSISTED FOR ABOUT 3-4 HOURS...THE INITIAL
INTENSITY WILL BE MAINTAINED AT 50 KT FOR THIS ADVISORY...BUT THE
50-KT WIND RADII DISTANCE HAS BEEN REDUCED FROM 45 NMI TO 15 NMI.

OTTO HAS ESSENTIALLY BEEN STATIONARY FOR THE PAST 6 HOURS...BUT A
SLOW DRIFT TO THE NORTHEAST...OR 325/02...IS EXPECTED TO BEGIN SOON
AND THAT IS THE MOTION USED FOR THIS ADVISORY. OTHERWISE...THERE
REMAINS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACKS OR
PHILOSOPHIES FOR THE PAST 24 HOURS. A LARGE DEEP-LAYER TROUGH ALONG
THE U.S. EAST COAST IS EXPECTED TO CONTINUE ITS EASTWARD TREK AND
GRADUALLY NUDGE OTTO TO THE NORTHEAST DURING THE NEXT 24 HOURS. BY
36-48 HOURS...HOWEVER...THE LARGE TROUGH IS FORECAST TO CAPTURE
OTTO AND ACCELERATE IT TO THE NORTHEAST AHEAD OF A STRONG COLD
FRONT. OTTO IS EXPECTED TO MERGE WITH THE FRONTAL SYSTEM BY 72
HOURS AND BECOME A SIGNIFICANT EXTRATROPICAL CYCLONE THAT COULD
AFFECT THE AZORES ISLANDS IN 96 TO 120 HOURS. THE OFFICIAL FORECAST
TRACK IS BASICALLY JUST AN UPDATE OF THE PREVIOUS TRACK AND IS
CLOSE TO THE CONSENSUS MODEL...TVCN.

NOW THAT OTTO HAS TRANSITIONED INTO A TROPICAL CYCLONE...THE STORM
HAS A BETTER CHANCE OF REACHING HURRICANE STATUS AS FORECAST BY THE
GFDL AND HWRF MODELS. THE VERTICAL SHEAR IS EXPECTED TO REMAIN
AROUND 10 KT OR LESS FOR THE NEXT 24 HOURS WHILE OTTO WILL BE OVER
28C OR WARMER SSTS. THE MUCH SMALLER INNER CORE WIND FIELD ALSO
SHOULD ALLOW FOR A MORE RAPID RESPONSE TO DEEP CONVECTION THAT
DEVELOPS NEAR THE CENTER. IN THE LATER FORECAST PERIODS...THE
INTENSITY HAS BEEN HELD A LITTLE HIGHER THAN WHAT WOULD TYPICALLY
BE EXPECTED FOR A CYCLONE EXPERIENCING SHEAR CONDITIONS OF 40-50 KT
DUE TO EXTRATROPICAL TRANSITION AND AN EXPECTED INFUSION OF
BAROCLINIC ENERGY THAT SHOULD HELP TO SUSTAIN THE CIRCULATION. THE
OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND
IS A BLEND OF THE NHC OBJECTIVE INTENSITY GUIDANCE.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/1500Z 23.8N  68.0W    50 KT
 12HR VT     08/0000Z 24.3N  67.1W    55 KT
 24HR VT     08/1200Z 25.7N  65.0W    60 KT
 36HR VT     09/0000Z 27.6N  61.8W    65 KT
 48HR VT     09/1200Z 29.8N  57.2W    60 KT
 72HR VT     10/1200Z 34.7N  45.2W    55 KT...POST-TROP/EXTRATROP
 96HR VT     11/1200Z 39.0N  32.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/1200Z 39.0N  25.0W    35 KT...POST-TROP/EXTRATROP
 
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FORECASTER STEWART
 
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