Tropical Storm RAFAEL

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TROPICAL STORM RAFAEL DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172012
1100 PM AST SAT OCT 13 2012
 
SATELLITE IMAGERY...RADAR DATA...AND SURFACE OBSERVATIONS INDICATE
THERE HAS BEEN LITTLE CHANGE IN THE STRUCTURE AND INTENSITY OF
RAFAEL DURING THE PAST FEW HOURS.  STRONG CONVECTIVE BANDS WITH
CLOUD TOPS COLDER THAN -80C ARE OCCURRING OVER THE EASTERN
SEMICIRCLE.  HOWEVER...THESE REMAIN RATHER LOOSELY ORGANIZED
NEAR THE CENTER.  THE CENTRAL PRESSURE IS 1004 MB BASED ON DATA
FROM ST. MARTIN...WHICH IS UNCHANGED FROM THE LAST HURRICANE HUNTER
AIRCRAFT FIX.  BASED ON THESE DATA AND A 45 KT SATELLITE INTENSITY
FROM TAFB...THE INITIAL INTENSITY REMAINS 45 KT.
 
THE CENTER HAS JUMPED AROUND SOME DURING THE PAST SEVERAL HOURS. 
HOWEVER...THE OVERALL MOTION IS NORTHWARD AT ABOUT 12 KT.  RAFAEL
SHOULD TURN TOWARD THE NORTH-NORTHWEST OR NORTHWEST DURING THE NEXT
24-36 HOURS AS A LOW/MID-LEVEL RIDGE BUILDS TO THE NORTH OF THE
CYCLONE.  AFTER THAT...A STRONG DEEP-LAYER TROUGH AND ASSOCIATED
SURFACE COLD FRONT WILL MOVE THROUGH THE EASTERN UNITED STATES
INTO THE WESTERN ATLANTIC.  THIS WILL BREAK THE RIDGE AND ALLOW
RAFAEL TO RECURVE INTO THE WESTERLIES.  WHILE ALL THE MODELS AGREE
WITH THIS SCENARIO...THERE REMAIN SOME DIFFERENCES IN THE DETAILS...
ESPECIALLY IN REGARDS TO THE FORWARD SPEED AFTER RECURVATURE.  THE
ECMWF...WHICH HAS THE WEAKEST DEPICTION OF THE STORM...REMAINS THE
SLOWEST AND FARTHEST SOUTH OF THE GUIDANCE.  THE GFS AND THE
CANADIAN MODELS...WHICH FORECAST A MUCH STRONGER RAFAEL...REMAIN
THE FASTEST AND MOST NORTHERLY.  THE NEW FORECAST TRACK IS SIMILAR
TO THE PREVIOUS TRACK IN COMPROMISING BETWEEN THESE EXTREMES AND IT
LIES NEAR...BUT SOMEWHAT FASTER THAN...THE CONSENSUS MODELS.

RAFAEL IS IN AN ENVIRONMENT OF MODERATE SOUTHWESTERLY VERTICAL WIND
SHEAR...AND THIS SHOULD CONTINUE FOR THE NEXT 36-48 HR.  THE
INTENSITY FORECAST CALLS FOR STRENGTHENING DURING THIS TIME IN BEST
AGREEMENT WITH THE SHIPS MODEL AND THE INTENSITY CONSENSUS.  AFTER
THAT...RAFAEL SHOULD ENCOUNTER INCREASING SHEAR WHICH SHOULD HALT
STRENGTHENING AND START A WEAKENING TREND.  THE CYCLONE IS FORECAST
TO BE EXTRATROPICAL BY 120 HR...AND THIS COULD HAPPEN EARLIER IF
THE FASTER AND MORE NORTHERLY MOTION OF THE GFS AND CANADIAN MODELS
OCCURS.
 
USERS ARE REMINDED NOT TO FOCUS ON THE EXACT TRACK OF THE CENTER
DURING THE NEXT DAY OR SO...SINCE HEAVY RAIN AND WIND IMPACTS
EXTEND WELL EAST AND SOUTHEAST OF THE CENTER.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  14/0300Z 18.4N  63.6W   45 KT  50 MPH
 12H  14/1200Z 19.9N  64.2W   55 KT  65 MPH
 24H  15/0000Z 21.6N  65.4W   60 KT  70 MPH
 36H  15/1200Z 23.4N  66.4W   65 KT  75 MPH
 48H  16/0000Z 25.8N  66.5W   70 KT  80 MPH
 72H  17/0000Z 33.5N  62.5W   70 KT  80 MPH
 96H  18/0000Z 44.5N  55.0W   55 KT  65 MPH
120H  19/0000Z 50.0N  46.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 
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