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Hurricane MICHAEL


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HURRICANE MICHAEL DISCUSSION NUMBER  26
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132012
1100 AM AST SUN SEP 09 2012
 
WHILE THE OVERALL SATELLITE APPEARANCE HAS NOT CHANGED MUCH THIS
MORNING...THERE SEEM TO BE SOME CHANGES OCCURRING WITHIN THE INNER
CORE OF MICHAEL.  THE EYE HAS INCREASED IN DIAMETER FROM 10 TO 25
N MI AT THE SAME TIME CLOUD TOP TEMPERATURES HAVE WARMED...POSSIBLY
INDICATIVE OF A MIXING EVENT WITHIN THE EYE.  DVORAK T-NUMBERS FROM
BOTH SATELLITE AGENCIES ARE AT 4.5 AT 1200 UTC...AND AN AVERAGE OF
RECENT ADT VALUES IS 5.2.  THE INITIAL INTENSITY IS LOWERED
SLIGHTLY TO 80 KT ON THIS ADVISORY BASED ON A BLEND OF THESE DATA
AND IN LIGHT OF THE RECENT STRUCTURAL CHANGES WITHIN THE INNER
CORE.
 
RECENT CENTER FIXES INDICATE THAT THE HURRICANE HAS TURNED TOWARD
THE WEST...AND THE INITIAL MOTION ESTIMATE IS A SLOW 275/04. GLOBAL
MODELS SHOW A POTENT SHORTWAVE TROUGH DIGGING TO THE EAST OF
MICHAEL DURING THE NEXT 24-36 HOURS. WHILE THIS FEATURE SHOULD HAVE
NO DIRECT EFFECT ON THE CYCLONE...RISING HEIGHTS IN THE WAKE OF THE
SHORTWAVE SHOULD ALLOW FOR A SLOW WESTERLY TO WEST- NORTHWESTERLY
COURSE DURING THE NEXT DAY OR SO. BY 48 HOURS... MICHAEL SHOULD
TURN NORTHWARD AND THEN NORTH-NORTHEASTWARD AT AN INCREASING
FORWARD SPEED AS IT REACHES THE FAST-PACED SOUTH-SOUTHWESTERLY FLOW
AHEAD OF A SHARP SHORTWAVE TROUGH CROSSING THE CANADIAN MARITIMES.
THE NHC TRACK FORECAST IS ADJUSTED A BIT TO THE LEFT THROUGH 48
HOURS AND SOMEWHAT TO THE EAST BY 72 HOURS...WITH THE FORECAST NEAR
THE MIDDLE OF THE GUIDANCE ENVELOPE.
 
ALTHOUGH THE WATERS ALONG THE TRACK OF MICHAEL ARE EXPECTED TO BE
WARM ENOUGH...THE CURRENT FAVORABLE ENVIRONMENT OF LIGHT SHEAR IS
ABOUT TO CHANGE.  WITHIN 24 HOURS...STRONG NORTHERLY WIND SHEAR
OVER MICHAEL IS EXPECTED TO DEVELOP AS THE CYCLONE PASSES FROM
SOUTH OF A RIDGE AXIS TO A POSITION UNDERNEATH THE OUTFLOW
ASSOCIATED WITH LESLIE.  ALTHOUGH THIS SHEAR SHOULD BE CONFINED TO
A NARROW LAYER IN THE UPPER TROPOSPHERE...IT  COULD BE OF A
MAGNITUDE THAT WOULD INDUCE A FASTER WEAKENING THAN FORECAST.  A
BRIEF REDUCTION IN SHEAR IS POSSIBLE AFTER THIS TIME BEFORE MICHAEL
ENCOUNTERS INCREASING SOUTH-SOUTHWESTERLY SHEAR ASSOCIATED WITH A
STRONG MID-LATITUDE JET.  A COMBINATION OF THE SHEAR AND RAPIDLY
DECREASING SEA SURFACE TEMPERATURES ALONG THE TRACK SHOULD MEAN
STEADY WEAKENING UNTIL THE CYCLONE BECOMES FRONTAL AROUND 72
HOURS.  THE NHC INTENSITY FORECAST IS NEARLY THE SAME AS THE
PREVIOUS ONE...AND IS CLOSE TO A BLEND OF SHIPS MODEL OUTPUT AND
THE LATEST INTENSITY CONSENSUS AIDS.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 33.7N  43.2W   80 KT  90 MPH
 12H  10/0000Z 33.8N  43.9W   80 KT  90 MPH
 24H  10/1200Z 34.0N  45.5W   75 KT  85 MPH
 36H  11/0000Z 35.1N  47.0W   65 KT  75 MPH
 48H  11/1200Z 38.1N  47.6W   55 KT  65 MPH
 72H  12/1200Z 46.5N  44.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  13/1200Z...DISSIPATED
 
$$
FORECASTER KIMBERLAIN
 
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