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 983 
 WTNT42 KNHC 130858
 TCDAT2
  
 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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