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Tropical Storm RAFAEL (Text)

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TROPICAL STORM RAFAEL DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172012
500 AM AST SAT OCT 13 2012
 
RAFAEL CONTINUES TO HAVE A DISHEVELED APPEARANCE IN SATELLITE
IMAGERY.  WHILE THE TROPICAL CYCLONE IS MAINTAINING A LARGE CLOUD
SHIELD...DEEP CONVECTION CONTINUES TO BE DISPLACED EAST OF THE
LOW-LEVEL CENTER DUE TO PERSISTENT STRONG SOUTHWESTERLY SHEAR. 
HOWEVER...CONVECTION HAS BEEN INCREASING IN INTENSITY AND
COVERAGE IN A BAND SOUTHEAST OF THE CENTER DURING THE PAST SEVERAL
HOURS.  MAXIMUM FLIGHT-LEVEL WINDS REPORTED BY AN AIR FORCE PLANE
FLYING AT 5000 FT WERE 40 KT AND PEAK SFMR WINDS WERE BETWEEN 35-40
KT...THOUGH SEVERAL OF THE HIGHER VALUES COULD BE RAIN
CONTAMINATED.  BASED ON THESE DATA...THE INITIAL INTENSITY IS KEPT
AT 35 KT.
 
RAFAEL APPEARS TO HAVE MOVED TO THE LEFT OF THE PREVIOUS ESTIMATE...
WITH THE LONG-TERM AVERAGE MOTION STILL TOWARD THE NORTHWEST OR
320/08.  IN THE SHORT TERM...THE CYCLONE IS EXPECTED TO BE STEERED
SLOWLY POLEWARD INTO A BREAK IN THE SUBTROPICAL RIDGE CREATED BY A
MID-LATITUDE SHORTWAVE PASSING THROUGH ATLANTIC CANADA.  BETWEEN
36-72 HOURS...THE TRACK GUIDANCE SHOWS RAFAEL JOGGING TOWARD THE
NORTHWEST OR EVEN WEST-NORTHWEST AS A LOW- TO MID-LEVEL RIDGE
TEMPORARILY BUILDS TO THE NORTH OF THE STORM.  BY DAY 3...A COMPLEX
BUT PROGRESSIVE SHORTWAVE OVER EASTERN NORTH AMERICA SHOULD CAUSE
RAFAEL TO RECURVE INTO THE WESTERLIES...FOLLOWED BY A NORTHEASTWARD
ACCELERATION.  WHILE THE CROSS-TRACK SPREAD OF THE MODEL GUIDANCE
IS GENERALLY MINIMAL...THE ALONG-TRACK SPREAD IS RATHER
SUBSTANTIAL.  ON ONE END OF THE SPECTRUM IS THE GFS WHICH MAINTAINS
A STRONGER REPRESENTATION OF RAFAEL THAT IS CAPTURED BY THE ABOVE-
MENTIONED SHORTWAVE.  THE ECMWF AND UKMET...ON THE OTHER
HAND...HAVE WEAKER VERSIONS OF THE STORM THAT ARE STEERED MORE
SLOWLY NORTHEASTWARD BY A WEAKER SHORTWAVE IN THE SOUTHERN STREAM. 
THE NHC TRACK FORECAST IS ADJUSTED TO THE LEFT AND IS SLOWER THAN
THE PREVIOUS ONE AS A RESULT OF SOME WEIGHT GIVEN TO THE ECMWF/UKMET
SOLUTIONS.

THERE IS GREATER-THAN-NORMAL UNCERTAINTY WITH REGARD TO THE
INTENSITY FORECAST. SOUTHWESTERLY SHEAR AFFECTING RAFAEL IS
FORECAST TO DECREASE DURING THE NEXT 24 HOURS AS THE COLD LOW
NORTHWEST OF THE CYCLONE SHEARS OUT.  THIS COULD ALLOW FOR A PERIOD
OF INTENSIFICATION FOR A DAY OR TWO...THOUGH THE ECMWF SHOWS
ENOUGH SOUTHWESTERLY SHEAR CONTINUING TO PRECLUDE MUCH
STRENGTHENING. REGARDLESS OF THAT...ALL MODELS SHOW INCREASING
SHEAR AFTER 72 HOURS AS WESTERLY FLOW INCREASES AHEAD OF THE
SHORTWAVE MOVING INTO THE WESTERN ATLANTIC AROUND THAT TIME. 
DESPITE THIS...HWRF...GFDL...AND SHIPS MODELS CONTINUE TO SHOW
RAFAEL REACHING HURRICANE STRENGTH.  THE INTENSITY FORECAST IS
INCREASED A BIT OVER THE PREVIOUS ONE...AND IS CLOSE TO THE
INTENSITY CONSENSUS AIDS.  EXTRATROPICAL TRANSITION IS INDICATED AT
DAY 5 IN AGREEMENT WITH GLOBAL MODEL OUTPUT.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0900Z 15.7N  64.2W   35 KT  40 MPH
 12H  13/1800Z 17.0N  64.5W   40 KT  45 MPH
 24H  14/0600Z 18.8N  65.1W   45 KT  50 MPH
 36H  14/1800Z 20.5N  65.8W   50 KT  60 MPH
 48H  15/0600Z 22.2N  66.8W   60 KT  70 MPH
 72H  16/0600Z 26.4N  67.0W   60 KT  70 MPH
 96H  17/0600Z 35.8N  62.9W   60 KT  70 MPH
120H  18/0600Z 45.0N  56.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN/AVILA
 
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