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Tropical Storm OTTO (Text)

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TROPICAL STORM OTTO DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 AM AST FRI OCT 08 2010
 
SATELLITE IMAGES INDICATE THAT DEEP AND SYMMETRIC CONVECTION HAS
INTENSIFIED NEAR THE CENTER OF OTTO DURING THE PAST SEVERAL HOURS
WITH AN OCCASIONAL HINT OF A WARM SPOT IN THE INFRARED CHANNEL. 
UNFORTUNATELY THERE HAVE BEEN NO RECENT MICROWAVE OVERPASSES TO
HELP LOCATE THE CENTER...WHICH HANDICAPS THE INTENSITY ESTIMATE. 
DVORAK NUMBERS FROM TAFB/SAB ARE 65/55 KT...AND A BLEND OF THESE
DATA GIVE AN INITIAL WIND SPEED OF 60 KT.  THE SHIPS MODEL SUGGESTS
THAT SOUTHWESTERLY SHEAR WILL RELAX NEAR OTTO DURING THE NEXT 24
HOURS...WHICH SHOULD ALLOW THE STORM TO BECOME A HURRICANE. 
GUIDANCE IS NOW IN AGREEMENT ON OTTO ATTAINING HURRICANE STRENGTH
LATER TODAY.  SINCE ANY SUBTROPICAL CHARACTERISTICS ARE NOW
GONE...I DO NOT SEE A GOOD REASON TO DISCOUNT THE GUIDANCE...AND
THE OFFICIAL FORECAST IS RAISED FROM THE PREVIOUS ONE...JUST BELOW
THE MODEL CONSENSUS.  WEAKENING SEEMS LIKELY IN A COUPLE OF DAYS
DUE TO WATERS COOLING BELOW 26C AND INCREASING SOUTHWESTERLY SHEAR.   

BASED PRIMARILY ON CONTINUITY FROM THE PREVIOUS FORECAST TRACK...THE
INITIAL MOTION IS 060/12.  OTTO IS BEING ACCELERATED GENERALLY
NORTHEASTWARD BY A LARGE MID-LATITUDE TROUGH OVER THE WESTERN
ATLANTIC OCEAN.  THE TROPICAL CYCLONE SHOULD BECOME EMBEDDED WITHIN
FAST SOUTHWESTERLY FLOW FOR THE NEXT TWO TO THREE DAYS...AND MODEL
GUIDANCE IS IN GOOD AGREEMENT ON THE TRACK DURING THAT TIME. 
HOWEVER...LARGE DISAGREEMENTS OCCUR IN THE LONG RANGE AS IT IS NOT
CLEAR WHETHER OTTO WILL REMAIN WITHIN THE MID-LATITUDE FLOW OR TURN
MORE TO THE EAST AND SOUTHEAST AROUND THE WEST SIDE OF A TROUGH
OVER THE FAR NORTHEASTERN ATLANTIC OCEAN.  THE MOST RELIABLE
GUIDANCE SHOW THE LATTER SOLUTION...AND THE OFFICIAL FORECAST WILL
STAY WITH THAT SCENARIO.  

EXTRATROPICAL TRANSITION WILL PROBABLY BEGIN AFTER THE CYCLONE
CROSSES 30N AS THE CYCLONE MOVES OVER COOLER WATERS AND INTO HIGHER
SHEAR.  FSU PHASE SPACE DIAGRAMS...HOWEVER...SUGGEST THAT OTTO WILL
RETAIN ITS WARM CORE FOR SEVERAL DAYS.  THE MODEL THICKNESS FIELDS
DO SHOW THE CYCLONE DEVELOPING FRONTAL FEATURES IN ABOUT THREE
DAYS... THUS EXTRATROPICAL STATUS IS SHOWN AT THAT TIME.  

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0900Z 24.8N  65.5W    60 KT
 12HR VT     08/1800Z 25.9N  63.6W    65 KT
 24HR VT     09/0600Z 28.0N  60.1W    70 KT
 36HR VT     09/1800Z 30.3N  55.2W    75 KT
 48HR VT     10/0600Z 33.2N  49.0W    70 KT
 72HR VT     11/0600Z 38.5N  34.0W    55 KT...POST-TROP/EXTRATROP
 96HR VT     12/0600Z 39.0N  25.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     13/0600Z 36.5N  21.5W    35 KT...POST-TROP/EXTRATROP
 
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FORECASTER BLAKE
 
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