Hurricane OTTO

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HURRICANE OTTO DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 PM AST FRI OCT 08 2010
 
ALTHOUGH THE CENTRAL DENSE OVERCAST FEATURE HAS DECREASED IN AREAL
COVERAGE...CLOUD TOP TEMPERATURES COLDER THAN -80C HAVE PERSISTED
NEAR THE UPPER-LEVEL CENTER. A 08/2217Z SSMIS MICROWAVE OVERPASS
INDICATED THE EYE IS TILTED SIGNIFICANTLY DOWNSTREAM TO THE
NORTHEAST BY AT LEAST 35 NMI BETWEEN THE LOW- AND MID-LEVEL
CIRCULATIONS. SUBJECTIVE SATELLITE INTENSITY ESTIMATES ARE T5.0/90
KT FROM TAFB AND T4.5/77 KT FROM SAB...AND AROUND 67 KT FROM THE
UW-CIMSS ADT PROGRAM. THEREFORE...THE INITIAL INTENSITY IS BEING
INCREASED TO 75 KT...AND OTTO HAS LIKELY PEAKED IN STRENGTH GIVEN
THE EYEWALL WAS OPEN AT ALL LEVELS IN THE AFOREMENTIONED SSMIS
MICROWAVE IMAGES.
 
THE INITIAL MOTION IS 060/18. WATER VAPOR IMAGERY INDICATES OTTO IS
NOW EMBEDDED WITHIN A DEEP-LAYER WEST-SOUTHWESTERLY FLOW ON THE
EAST SIDE OF A MASSIVE MID-LATITUDE TROUGH THAT EXTENDS SOUTHWARD
FROM THE CANADIAN MARITIME PROVINCES TO THE NORTHERN BAHAMAS. THIS
FLOW REGIME SHOULD CONTINUE TO ACCELERATE OTTO TO THE NORTHEAST OR
EAST-NORTHEAST FOR THE NEXT 72 HOURS OR SO...WHICH IS CONSISTENT
WITH ALL OF THE NHC MODEL GUIDANCE. AFTER THAT...HOWEVER...THE
GUIDANCE REMAINS DIVERGENT ON WHETHER OTTO WILL CONTINUE TO MOVE TO
THE NORTHEAST OR SLOW DOWN AND TURN SOUTHEASTWARD TOWARD THE AZORES
ISLANDS.  THERE IS MUCH LESS SPREAD IN THE MODEL SOLUTIONS FOR THIS
RUN COMPARED TO THE PREVIOUS ADVISORY...SO THE FORECAST TRACK HAS
BEEN SHIFTED SLIGHTLY NORTHWARD WITH A NOTED DECREASE IN FORWARD
SPEED. OVERALL...THE OFFICIAL FORECAST IS SIMILAR TO THE CONSENSUS
MODEL...TVCN...THROUGH 72 HOURS...AND THEN A LITTLE SOUTH OF THAT
MODEL AT 96 AND 120 HOURS.
 
CONVENTIONAL INFRARED SATELLITE POSITION ESTIMATES INDICATE THAT THE
UPPER-LEVEL CIRCULATION IS OUTRUNNING THE LOW-LEVEL CENTER NOTED IN
MICROWAVE DATA BY MORE THAN 60 NMI...SO GRADUAL WEAKENING IS
FORECAST SINCE OTTO WILL BE MOVING OVER PROGRESSIVELY COOLER SSTS
AND EXPERIENCING INCREASING SOUTHWESTERLY VERTICAL SHEAR. TIMING
POSSIBLE DECOUPLING OF THE LOWER- AND UPPER-LEVEL CIRCULATIONS IS
TRICKY. HOWEVER...SINCE OTTO WILL BE MOVING OVER SUB-23C SSTS...BE
UNDERNEATH VERTICAL SHEAR CONDITIONS EXCEEDING 40 KT...AND POSSIBLY
MERGE WITH A FRONTAL ZONE BY 48 HOURS...OTTO IS EXPECTED TO BEGIN
EXTRATROPICAL TRANSITION BETWEEN 36-48 HOURS. THE INTENSITY
FORECAST IS SIMILAR TO BUT SLIGHTLY LOWER THAN A BLEND OF THE NHC
INTENSITY GUIDANCE...DUE IN PART TO THE TILTED VORTEX STRUCTURE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0300Z 27.8N  60.8W    75 KT
 12HR VT     09/1200Z 29.7N  57.4W    70 KT
 24HR VT     10/0000Z 32.6N  51.7W    70 KT
 36HR VT     10/1200Z 36.1N  44.4W    65 KT
 48HR VT     11/0000Z 40.0N  36.4W    60 KT...POST-TROP/EXTRATROP
 72HR VT     12/0000Z 43.0N  28.0W    50 KT...POST-TROP/EXTRATROP
 96HR VT     13/0000Z 43.0N  23.5W    40 KT...POST-TROP/EXTRATROP
120HR VT     14/0000Z 40.0N  20.0W    40 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 
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