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Hurricane NADINE (Text)

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HURRICANE NADINE DISCUSSION NUMBER  69
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
500 PM AST SAT SEP 29 2012
 
ALTHOUGH ANALYSES FROM UW-CIMSS AND THE SHIPS MODEL CONTINUE TO SHOW
20 KT OF SOUTHWESTERLY VERTICAL WIND SHEAR...NADINE HAS CONTINUED
TO BECOME BETTER ORGANIZED.  THE EYE HAS BECOME MORE APPARENT IN
VISIBLE AND INFRARED IMAGERY...AND THERE HAS BEEN AN INCREASE IN
BANDING AROUND THE EYE.  A RECENT SSM/IS OVERPASS SHOWS THAT THE
EYE IS TILTED TOWARD THE NORTH...BUT THE TILT IS LESS THAN THIS
TIME YESTERDAY.  WHILE SATELLITE INTENSITY ESTIMATES ARE 65 KT FROM
TAFB AND SAB...THE CIMSS ADT ESTIMATE IS NEAR 80 KT...THE LATEST
AMSU ESTIMATES FROM CIMSS AND CIRA ARE IN THE 70-80 KT RANGE...AND
THE LATEST CIMSS SATCON ESTIMATE IS 78 KT.  BASED ON THIS...THE
INITIAL INTENSITY IS INCREASED TO 70 KT...AND THIS COULD BE A
LITTLE CONSERVATIVE.
 
THE INITIAL MOTION IS 345/13.  NADINE IS BETWEEN A DEEP-LAYER RIDGE
TO THE EAST AND A MID-/UPPER-LEVEL LOW TO THE WEST.  THE GLOBAL
MODELS FORECAST THE CYCLONE TO MERGE WITH THE LOW BETWEEN 24-72
HR...WITH THE SYSTEM THEN CAUGHT IN AN AREA OF LIGHT STEERING
CURRENTS.  THE DYNAMICAL MODELS ARE IN GOOD AGREEMENT THAT NADINE
WILL SLOW DOWN AND MAKE A CYCLONIC LOOP DURING THE NEXT 96 HR.
THE CANADIAN MODEL FORECASTS THE LARGEST LOOP...WITH THE CENTER OF
NADINE MOVING SOUTHWARD TO 30N BEFORE TURNING EASTWARD.  THE NEW
FORECAST TRACK SHOWS MORE SOUTHWARD MOTION DURING THE LOOP THAN THE
PREVIOUS FORECAST...BUT STILL NOT AS MUCH AS FORECAST BY THE
DYNAMICAL MODELS.  AFTER 96 HR...THE GLOBAL MODELS FORECAST A LARGE
BAROCLINIC CYCLONE TO DEVELOP OVER THE NORTHEASTERN ATLANTIC WITH
THE ASSOCIATED WESTERLY WINDS EXTENDING SOUTHWARD TO AT LEAST 30N. 
THIS SYSTEM SHOULD STEER NADINE TO THE EAST OR NORTHEAST NEAR THE
END OF THE FORECAST PERIOD.

NADINE DOES NOT APPEAR AS SHEARED AS THE CIMSS/SHIPS-ANALYZED SHEAR
SUGGESTS...AND IT MAY BE THAT A MID-/UPPER-LEVEL TROUGH SHORTWAVE
TROUGH JUST SOUTH OF THE SYSTEM IS PARTIALLY SHELTERING IT.  THIS
TROUGH COULD ALSO PROVIDE SOME FAVORABLE UPPER-LEVEL DIVERGENCE...
AND THE INTENSITY FORECAST THUS CALLS FOR A LITTLE MORE
STRENGTHENING DURING THE FIRST 12 HR.  FROM 24-72 HR...NADINE
COULD ENCOUNTER DECREASING SHEAR AS IT MERGES WITH THE
MID-/UPPER-LEVEL LOW.  HOWEVER...THIS MERGER IS LIKELY TO AT LEAST
SOMEWHAT DISRUPT THE STRUCTURE...AND THE NEW INTENSITY FORECAST
FOLLOWS THE PREVIOUS FORECAST IN CALLING FOR WEAKENING DURING THIS
TIME.  LATE IN THE FORECAST PERIOD...INTERACTION BETWEEN NADINE AND
THE BAROCLINIC CYCLONE SHOULD LEAD TO EXTRATROPICAL TRANSITION. 
THE FORECAST CALLS FOR THIS AT 120 HR...ALTHOUGH IT COULD BE
DELAYED IF NADINE IS SOUTH OF THE CURRENT FORECAST TRACK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/2100Z 34.4N  36.7W   70 KT  80 MPH
 12H  30/0600Z 35.8N  37.4W   75 KT  85 MPH
 24H  30/1800Z 36.7N  38.2W   70 KT  80 MPH
 36H  01/0600Z 36.5N  38.7W   65 KT  75 MPH
 48H  01/1800Z 35.9N  39.0W   60 KT  70 MPH
 72H  02/1800Z 35.0N  39.0W   55 KT  65 MPH
 96H  03/1800Z 35.0N  37.0W   50 KT  60 MPH
120H  04/1800Z 38.5N  32.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 
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