Tropical Storm OTTO

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TROPICAL STORM OTTO DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 AM AST SUN OCT 10 2010
 
RECENT SATELLITE IMAGERY SHOWS THE DEVELOPMENT OF FRONTAL CLOUD
BANDS AND ALSO INDICATES THAT COOL DRY AIR HAS WRAPPED AROUND THE
SOUTHERN SEMICIRCLE OF OTTO AND INTO THE CENTER.  THE REMAINING
CONVECTION IS NOW NORTH AND WEST OF THE CENTER AND AMSU TEMPERATURE
PROFILES SHOW THAT THE UPPER-LEVEL WARM CORE HAS WEAKENED. BASED ON
ALL OF THIS...OTTO IS NOW A POST-TROPICAL EXTRATROPICAL CYCLONE...
AND THIS WILL BE THE LAST NHC ADVISORY. THE INITIAL INTENSITY IS
HELD AT 55 KT...AND SLOW WEAKENING SHOULD BEGIN LATER TODAY AS OTTO
MOVES AWAY FROM THE BEST BAROCLINIC DYNAMICS. GRADUAL WEAKENING IS
EXPECTED TO CONTINUE FOR THE REST OF THE PERIOD. HOWEVER...IT IS
WORTH NOTING THAT THE GFS AND ECMWF STRENGTHEN OTTO A LITTLE AT THE
END OF THE PERIOD...SO THE OFFICIAL FORECAST COULD BE A LITTLE LOW
ON DAYS 4 AND 5.

OTTO IS RACING TOWARD THE NORTHEAST AT 35 TO 40 KNOTS...EMBEDDED
WITHIN DEEP-LAYER SOUTHWESTERLY FLOW TO THE SOUTHEAST OF A LARGE
MID/UPPER-LEVEL TROUGH CENTERED BETWEEN 55W AND 60W.  THE GLOBAL
MODELS ARE IN GENERALLY GOOD AGREEMENT IN SHOWING POST-TROPICAL OTTO
ESCAPING THE WESTERN ATLANTIC TROUGH AND TURNING EASTWARD AND THEN
SOUTHEASTWARD WITHIN 48 HOURS AS IT COMES UNDER THE INFLUENCE OF A
DEEP-LAYER LOW CENTERED OVER THE IBERIAN PENINSULA AND WESTERN
MEDITERRANEAN SEA. LATE IN THE PERIOD THE DEEP-LAYER LOW MOVES
EAST...LEAVING OTTO BEHIND TO MOVE SLOWLY EASTWARD OR NORTHEASTWARD
BY DAY 5. THE OFFICIAL FORECAST IS BASED ON A CONSENSUS OF THE GFS
...UKMET...ECMWF...AND CANADIAN GLOBAL MODELS.

FUTURE INFORMATION ON POST-TROPICAL OTTO CAN BE FOUND IN HIGH SEAS
FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE UNDER AWIPS HEADER
NFDHSFAT1 AND WMO HEADER FZNT01 KWBC...AND BY METEO-FRANCE UNDER WMO
HEADER FQNT50 LFPW. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 37.3N  41.1W    55 KT...POST-TROP/EXTRATROP
 12HR VT     11/0000Z 40.0N  35.6W    50 KT...POST-TROP/EXTRATROP
 24HR VT     11/1200Z 42.6N  29.7W    45 KT...POST-TROP/EXTRATROP
 36HR VT     12/0000Z 43.0N  26.3W    45 KT...POST-TROP/EXTRATROP
 48HR VT     12/1200Z 41.5N  24.1W    40 KT...POST-TROP/EXTRATROP
 72HR VT     13/1200Z 37.0N  22.0W    35 KT...POST-TROP/EXTRATROP
 96HR VT     14/1200Z 36.0N  20.5W    30 KT...POST-TROP/EXTRATROP
120HR VT     15/1200Z 37.0N  19.5W    30 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 
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