Subtropical Storm OTTO

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SUBTROPICAL STORM OTTO DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 AM AST THU OCT 07 2010

OTTO HAS BEEN STRUGGLING TO PRODUCE MUCH CONVECTION DURING THE
OVERNIGHT HOURS.  A CURVED OUTER BAND PERSISTS IN THE SOUTHERN
SEMICIRCLE OF THE STORM...WITH A SMALL AMOUNT OF CONVECTION NEAR
THE CENTER.  SINCE THE CLOUD PATTERN HAS DETERIORATED A LITTLE
BIT...THE MAXIMUM WINDS ARE REDUCED TO 50 KT...IN AGREEMENT WITH
VARIOUS SATELLITE INTENSITY ESTIMATES FROM 35 TO 50 KT.  IF THE
CONVECTION NEAR THE CENTER CONTINUES...THEN OTTO WILL LIKELY
TRANSITION INTO A TROPICAL STORM LATER TODAY.  THE SYSTEM STILL HAS
DAY OR TWO OF LIGHT SHEAR CONDITIONS AND WARM WATER TO INTENSIFY. 
IN FACT...ALL OF THE GUIDANCE SHOW OTTO BECOMING A HURRICANE...AND
THE NHC FORECAST WILL GO ALONG WITH THAT SCENARIO.  HOWEVER...OTTO
PROBABLY NEEDS TO SHED ITS SUBTROPICAL CHARACTERISTICS TO TAKE
ADVANTAGE OF THE FAVORABLE ENVIRONMENT.  SINCE THE SYSTEM IS STILL
RETAINING SOME SUBTROPICAL FEATURES...THE NHC FORECAST REMAINS
BELOW THE MODEL CONSENSUS.  GLOBAL MODELS SHOW OTTO BECOMING
EMBEDDED WITHIN A FRONTAL ZONE BY 72 HR...SO EXTRATROPICAL STATUS
IS INDICATED IN THE OFFICIAL FORECAST AT THAT TIME.

THE STORM HAS NOT BEEN MOVING MUCH DURING THE PAST FEW HOURS AND IS
ONLY DRIFTING NORTHWARD.  INITIALLY...OTTO IS IN AN AREA OF LIGHT
STEERING CURRENTS BETWEEN A DISTANT RIDGE OVER THE EAST-CENTRAL
ATLANTIC OCEAN AND A MID-LATITUDE TROUGH OVER THE WESTERN ATLANTIC. 
THE TROUGH IS EXPECTED TO DIG SOUTHEASTWARD TODAY...WHICH SHOULD
STEER OTTO MORE TO THE NORTHEAST AND CAUSE A FASTER FORWARD SPEED
AS THE STORM MOVES IN FASTER FLOW BETWEEN THE RIDGE AND THE TROUGH.
WHILE THE MODEL GUIDANCE REMAINS WELL CLUSTERED ON THIS SYNOPTIC
PATTERN...THERE ARE SOME NOTABLE SPEED DIFFERENCES...AS THE
GFDL/HWRF ARE MUCH FASTER THAN THE REST OF THE GUIDANCE.  FOR NOW
THE TRACK FORECAST WILL STAY CLOSER TO THE GLOBAL MODELS...SHOWING
A SLOWER FORWARD MOTION...AND THE PREVIOUS NHC FORECAST.  THE
96 AND 120 HR POSITIONS OF OTTO MAY HAVE TO BE ADJUSTED SOUTHWARD
LATER TODAY DUE TO THE POSSIBILITY THAT THE CYCLONE GETS CAUGHT UP
IN NORTHWESTERLY FLOW FROM A TROUGH EAST OF THE AZORES...RATHER
THAN MID-LATITUDE SOUTHWESTERLY FLOW AS EARLIER MODEL RUNS WERE
INDICATING.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 23.6N  68.2W    50 KT
 12HR VT     07/1800Z 24.0N  67.7W    55 KT
 24HR VT     08/0600Z 25.1N  66.0W    60 KT
 36HR VT     08/1800Z 26.8N  63.3W    65 KT
 48HR VT     09/0600Z 28.8N  59.7W    60 KT
 72HR VT     10/0600Z 33.5N  48.5W    55 KT...POST-TROP/EXTRATROP
 96HR VT     11/0600Z 38.5N  35.0W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/0600Z 41.0N  25.0W    35 KT...POST-TROP/EXTRATROP
 
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FORECASTER BLAKE
 
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