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Tropical Storm RAFAEL (Text)

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TROPICAL STORM RAFAEL DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172012
500 AM AST SUN OCT 14 2012
 
SATELLITE IMAGERY...RADAR DATA...AND SURFACE OBSERVATIONS INDICATE
RAFAEL HAS CONTINUED TO MOVE NORTHWARD TO NORTH-NORTHWESTWARD OVER
THE PAST 6 HOURS. DOPPLER RADAR DATA FROM SAN JUAN ALSO INDICATES A
NARROW BAND OF CONVECTION HAS NOW WRAPPED COMPLETELY AROUND THE
CIRCULATION CENTER...SUGGESTING THAT THE CYCLONE IS GETTING BETTER
ORGANIZED. FURTHERMORE...INFRARED AND WATER VAPOR SATELLITE IMAGERY
INDICATE THE CIRRUS OUTFLOW PATTERN HAS EXPANDED IN THE WESTERN
SEMICIRCLE...WHICH IS AN INDICATION THAT THE VERTICAL SHEAR HAS
LESSENED. HOWEVER...THE OUTFLOW PATTERN IS STILL ELONGATED IN A 
NORTH-SOUTH CONFIGURATION. THE INITIAL INTENSITY IS BEING
MAINTAINED AT 45 KT...GIVEN THAT CLOUD TOPS HAVE CONTINUED TO COOL
AND THE ADT INTENSITY ESTIMATES HAVE BEEN STEADY AT T3.1/47 KT
SINCE THE PREVIOUS ADVISORY.

THE INITIAL MOTION ESTIMATE IS 340/11 KT. A FAIR PRESENTATION IN THE
REFLECTIVITY AND DOPPLER VELOCITY DATA FROM SAN JUAN SUGGEST THAT
RAFAEL HAS STARTED TO TURN TOWARD THE NORTH-NORTHWEST. THIS MOTION
IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS OR SO AS A DEEP-LAYER
RIDGE BUILDS TO THE NORTH OF THE CYCLONE AND GRADUALLY SLIDES
EASTWARD. AFTER THAT...A STRONG MID-TROPOSPHERIC TROUGH AND AN
ASSOCIATED COLD FRONT ARE FORECAST TO MOVE ACROSS THE EASTERN UNITED
STATES INTO THE WESTERN ATLANTIC BY 48 HOURS. THESE FEATURES ARE
EXPECTED TO ERODE THE RIDGE TO THE NORTH OF RAFAEL...AND ALLOW
CYCLONE TO RECURVE INTO THE HIGH-LATITUDE WESTERLIES. THE NHC
GUIDANCE IS IN EXCELLENT AGREEMENT ON THIS DEVELOPING SCENARIO...
EXCEPT FOR SLIGHT SPEED DIFFERENCES. THE 00Z ECMWF APPEARS TO BE A
SLIGHT OUTLIER AFTER 72 HOURS...AND IS THE RIGHTMOST OF ALL OF THE
MODELS DUE ITS MORE RAPID WEAKENING OF THE CYCLONE. THE OFFICIAL
NHC FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND LIES IN
THE MIDDLE OF THE TIGHTLY PACKED GUIDANCE ENVELOPE.
 
RAFAEL REMAINS IN A MODERATE SOUTHWESTERLY VERTICAL SHEAR
ENVIRONMENT...WHICH IS EXPECTED TO CONTINUE FOR THE NEXT 36-48 HR. 
HOWEVER...THERE MAY BRIEF PERIODS WHERE THE SHEAR ABATES...SUCH AS
HAS BEEN HAPPENING SINCE THE PREVIOUS ADVISORY...THAT WILL ALLOW
FOR RAFAEL TO STRENGTHEN. THE OFFICIAL INTENSITY FORECAST CONTINUES
THE STRENGTHENING TREND FROM THE PREVIOUS ADVISORIES FOR THE NEXT
48 HOURS OR SO...FOLLOWED BY GRADUAL WEAKENING AS THE VERTICAL
SHEAR INCREASES SHARPLY. THE OFFICIAL FORECAST IS SIMILAR TO THE
PREVIOUS ADVISORY AND CLOSELY FOLLOWS THE INTENSITY CONSENSUS
MODELS. RAFAEL IS FORECAST TO BECOME EXTRATROPICAL BY 120 HR...IF
NOT SOONER...WHEN THE CYCLONE BEGINS TO INTERACT WITH THE
AFOREMENTIONED STRONG COLD FRONT.
 
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  14/0900Z 19.4N  63.8W   45 KT  50 MPH
 12H  14/1800Z 20.7N  64.5W   55 KT  65 MPH
 24H  15/0600Z 22.5N  65.7W   60 KT  70 MPH
 36H  15/1800Z 24.1N  66.0W   65 KT  75 MPH
 48H  16/0600Z 27.1N  65.3W   70 KT  80 MPH
 72H  17/0600Z 36.2N  60.4W   65 KT  75 MPH
 96H  18/0600Z 46.1N  52.4W   55 KT  65 MPH
120H  19/0600Z 50.4N  44.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 
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