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Tropical Storm OTTO (Text)

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TROPICAL STORM OTTO DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 PM AST THU OCT 07 2010
 
A LITTLE BIT OF WESTERLY SHEAR IS AFFECTING OTTO...AND THE LOW-LEVEL
CENTER IS EMBEDDED BENEATH THE WESTERN SIDE OF A NEARLY CIRCULAR
AREA OF DEEP CONVECTION.  SATELLITE INTENSITY ESTIMATES ARE T3.5/55
KT AND T3.0/45 KT FROM TAFB AND SAB...RESPECTIVELY...AND THE
INITIAL INTENSITY WILL BE MAINTAINED AT 50 KT.  STRENGTHENING IS
STILL POSSIBLE DURING THE NEXT 48 HOURS SINCE THE VERTICAL SHEAR IS
EXPECTED TO BE RELATIVELY LIGHT.  THE ONE BIG CHANGE IN THE
INTENSITY GUIDANCE IS THAT MOST OF THE MODELS NOW SHOW A PEAK IN
INTENSITY OCCURRING AROUND 48 HOURS...WHICH IS ABOUT 12 HOURS LATER
THAN INDICATED IN THE PREVIOUS ADVISORY.  THE NEW FORECAST...
THEREFORE...DOES NOT SHOW WEAKENING COMMENCING UNTIL AFTER 48
HOURS.  THIS SOLUTION IS CLOSE TO THE STATISTICAL AND GLOBAL
GUIDANCE BUT TENDS TO DISREGARD THE HWRF AND GFDL SINCE THOSE
MODELS APPEAR TO DISSIPATE OTTO TOO SOON.

THE INITIAL MOTION IS 070/8.  THE CYCLONE IS BEING PICKED UP BY A
LARGE MID/UPPER-LEVEL TROUGH OVER THE WESTERN ATLANTIC AND IS
EXPECTED TO BECOME EMBEDDED WITHIN FAST MID-LATITUDE WESTERLIES
OVER THE NEXT 24-48 HOURS.  BY THE END OF THE FORECAST...MODEL
GUIDANCE SUGGESTS THAT THE FLOW WILL SPLIT WITH THE POST-TROPICAL
CYCLONE TAKING THE SOUTHERN ROUTE AND SLOWING DOWN AS IT NEARS THE
AZORES.  THE OFFICIAL FORECAST IS NOT MUCH DIFFERENT FROM THE
PREVIOUS ONE AND GENERALLY LIES BETWEEN THE FASTER ECMWF AND SLOWER
GFS.

THE FSU PHASE SPACE DIAGRAMS SHOW THAT OTTO SHOULD BEGIN
EXTRATROPICAL TRANSITION IN THE NEXT 24-36 HOURS...BUT THEY ALSO
SUGGEST THAT IT WILL NOT BECOME A DEEP COLD-CORE SYSTEM WITHIN THE
5-DAY FORECAST PERIOD.  AS SUCH...CONFIDENCE IS NOT HIGH THAT OTTO
WILL BECOME COMPLETELY EXTRATROPICAL BY 72 HOURS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0300Z 24.1N  66.6W    50 KT
 12HR VT     08/1200Z 24.9N  65.1W    55 KT
 24HR VT     09/0000Z 26.7N  62.0W    55 KT
 36HR VT     09/1200Z 29.0N  57.6W    60 KT
 48HR VT     10/0000Z 31.4N  52.1W    60 KT
 72HR VT     11/0000Z 36.5N  38.5W    50 KT...POST-TROP/EXTRATROP
 96HR VT     12/0000Z 39.0N  27.0W    45 KT...POST-TROP/EXTRATROP
120HR VT     13/0000Z 36.5N  23.0W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BERG
 
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