Hurricane JUAN

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HURRICANE JUAN DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT FRI SEP 26 2003

JUAN HAS SHOWED AN EYE OR WARM SPOT FOR THE PAST SEVERAL HOURS AND
IS GENERATING CONVECTION AS COLD AS -70C IN THE WESTERN SEMICIRCLE.
THE CIRRUS OUTFLOW IS FAIR TO GOOD OVER THE NORTHEASTERN
SEMICIRCLE...AND POOR OR RESTRICTED TO THE SOUTHWEST AS UPPER-LEVEL
WESTERLIES IMPINGE ON THE HURRICANE.  SATELLITE INTENSITY ESTIMATES
ARE 77 KT FROM AFWA AND TAFB...AND 65 KT FROM SAB.  THE INITIAL
INTENSITY IS RAISED TO 70 KT.

THE INITIAL MOTION IS A LITTLE TO THE RIGHT OF THE PREVIOUS
TRACK...360/7.  OTHER THAN THAT...THERE IS LITTLE CHANGE IN THE
SYNOPTIC PATTERN OR FORECAST PHILOSOPHY.  A DEEP-LAYER RIDGE OVER
THE NORTH CENTRAL ATLANTIC AND A DEEP-LAYER TROUGH OVER THE EASTERN
UNITED STATES SHOULD STEER JUAN ON A NORTHWARD TO NORTH-
NORTHWESTWARD TRACK WITH GRADUAL ACCELERATION THROUGH 48 HR.  THIS
SHOULD BE FOLLOWED BY A NORTH-NORTHEASTWARD MOTION AS JUAN GETS
ABSORBED INTO THE TROUGH.  ALL GUIDANCE AGREES WITH THIS
SCENARIO...AND THE OFFICIAL FORECAST BRINGS THE CENTER TO THE SOUTH
COAST OF NOVA SCOTIA IN ABOUT 48 HR.
 
ALL LARGE-SCALE MODELS FORECAST THE UPPER-LEVEL TROUGH CURRENTLY
AFFECTING JUAN TO WEAKEN...LEAVING THE HURRICANE TO MOVE THROUGH AN
AREA OF LIGHT TO MODERATE SHEAR THROUGH 36 HR.  SHOULD THIS
VERIFY...JUAN COULD STRENGTHEN MORE THAN CURRENTLY FORECAST BEFORE
IT REACHES THE COLD WATER NORTH OF THE GULF STREAM.  HOWEVER...
WATER VAPOR IMAGERY SUGGESTS THE MODELS MIGHT BE A LITTLE TOO FAST
IN WEAKENING THE SHEAR...AS A STRONG BAND OF UPPER-LEVEL WESTERLY
TO NORTHWESTERLY FLOW IS JUST SOUTHWEST OF JUAN.  THE INTENSITY
FORECAST WILL GO WITH THE SCENARIO THAT THE CONDITIONS WILL BE LESS
FAVORABLE THAN SHOWN IN THE MODELS BUT MORE FAVORABLE THAN
CURRENTLY SEEN IN THE IMAGERY...AND THUS CALL FOR A LITTLE MORE
STRENGTHENING.  JUAN SHOULD START TO WEAKEN ONCE IT MOVES NORTH OF
THE GULF STREAM...AND IT SHOULD BECOME EXTRATROPICAL BY 72 HR.

FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/0300Z 33.7N  61.9W    70 KT
 12HR VT     27/1200Z 35.1N  62.1W    75 KT
 24HR VT     28/0000Z 37.2N  62.8W    75 KT
 36HR VT     28/1200Z 40.1N  63.2W    75 KT
 48HR VT     29/0000Z 44.8N  62.8W    65 KT
 72HR VT     30/0000Z 57.1N  58.9W    40 KT...EXTRATROPICAL
 96HR VT     01/0000Z...ABSORBED BY LARGER EXTRATROPICAL LOW
 
 
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