Tropical Storm RAFAEL

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TROPICAL STORM RAFAEL DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172012
500 PM AST SAT OCT 13 2012
 
AIRCRAFT DATA AND SURFACE OBSERVATIONS INDICATE THAT THE CENTER OF
RAFAEL HAS BEEN REFORMING CLOSER TO THE DEEP CONVECTION OVER THE
PAST FEW HOURS. THE AIRCRAFT MEASURED A CENTRAL PRESSURE OF 1004 MB
AND A PEAK 850-MB FLIGHT-LEVEL WIND OF 56 KT. BASED ON THAT DATA
THE INITIAL INTENSITY IS RAISED TO 45 KT FOR THIS ADVISORY. THE
CLOUD PATTERN OF RAFAEL CONTINUES TO GRADUALLY IMPROVE...WITH A
LARGE AREA OF VERY COLD CLOUD TOPS NOTED TO THE NORTHEAST OF THE
CENTER LOCATION AND A LITTLE MORE CURVATURE NOTED TO THE MAIN
CONVECTIVE BAND TO THE SOUTHEAST. MOST OF THE GUIDANCE SUGGESTS
THAT CONDITIONS WILL SUPPORT STEADY STRENGTHENING FOR THE NEXT 2 TO
3 DAYS...AND SO DOES THE OFFICIAL FORECAST. THE NHC FORECAST IS A
LITTLE HIGHER THAN THE PREVIOUS ONE DUE TO THE OBSERVED
STRENGTHENING...AND IS NOW CLOSE TO THE IVCN INTENSITY CONSENSUS
THROUGH 72 HOURS. AFTER THAT TIME...SOUTHWESTERLY SHEAR SHOULD
INCREASE MARKEDLY AS RAFAEL INTERACTS WITH A DEEP-LAYER TROUGH
MOVING OFF THE U.S. EAST COAST. THIS SHOULD RESULT IN GRADUAL
WEAKENING AS THE CYCLONE UNDERGOES EXTRATROPICAL TRANSITION...WHICH
SHOULD BE COMPLETE BY DAY 5.
 
WITH THE RECENT NORTH-NORTHEASTWARD REFORMATION OF THE CENTER THE
INITIAL MOTION ESTIMATE OF 015/10 IS HIGHLY UNCERTAIN...AND
ADDITIONAL JUMPS IN THE CENTER LOCATION ARE POSSIBLE IN THE NEXT
FEW HOURS AS THE SYSTEM CONSOLIDATES. WHILE THE OVERALL TRACK
FORECAST REASONING HAS NOT CHANGED...THE RELOCATION OF THE CENTER
HAS RESULTED IN AN EASTWARD ADJUSTMENT OF THE NHC TRACK FORECAST BY
ABOUT A DEGREE FOR THE FIRST 36 HOURS. MOST OF THE GUIDANCE
SUGGESTS THAT RAFAEL WILL MOVE GENERALLY NORTHWARD FOR THE FIRST 12
HOURS OR SO AND THEN TURN NORTH-NORTHWESTWARD AND NORTHWESTWARD AS
A MID-LEVEL RIDGE TEMPORARILY BUILDS TO THE NORTHEAST OF THE
CYCLONE THROUGH 48 HOURS. AFTER THAT TIME...THERE CONTINUES TO BE
LARGE ALONG-TRACK SPREAD IN THE GUIDANCE...DUE TO DETAIL
DIFFERENCES IN HOW RAFAEL INTERACTS WITH THE AFOREMENTIONED TROUGH
MOVING OFF THE U.S. EAST COAST. GIVEN THE LARGE UNCERTAINTY...THE
ONLY SIGNIFICANT CHANGE TO THE NHC TRACK AT DAYS 3 THROUGH 5 WAS AN
INCREASE IN FORWARD SPEED TOWARD THE NEW MODEL CONSENSUS. THE NHC
FORECAST IS NEAR THE MIDDLE OF THE GUIDANCE EVELOPE AND LIES
BETWEEN THE TVCA MULTI-MODEL CONSENSUS AND THE GEFS ENSEMBLE MEAN
THROUGH THE END OF THE PERIOD.
 
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  13/2100Z 17.3N  63.3W   45 KT  50 MPH
 12H  14/0600Z 18.7N  63.7W   50 KT  60 MPH
 24H  14/1800Z 20.9N  64.8W   55 KT  65 MPH
 36H  15/0600Z 22.6N  66.0W   60 KT  70 MPH
 48H  15/1800Z 24.4N  66.5W   65 KT  75 MPH
 72H  16/1800Z 31.5N  64.0W   70 KT  80 MPH
 96H  17/1800Z 43.0N  57.0W   55 KT  65 MPH
120H  18/1800Z 50.5N  48.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 
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