Tropical Storm RAFAEL

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TROPICAL STORM RAFAEL DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172012
500 AM AST MON OCT 15 2012
 
THE CONVECTIVE CLOUD PATTERN OF RAFAEL HAS CONTINUED TO IMPROVE AND
A LARGE CDO FEATURE HAS NOW DEVELOPED OVER THE LOW-LEVEL CENTER.
SATELLITE INTENSITY ESTIMATES ARE T4.0/65 KT FROM TAFB...T3.5/55 KT
FROM SAB...AND ADT ESTIMATES ARE T3.4/53 KT...BUT WITH RAW DATA
T-NUMBERS OF T4.3/72 KT. ALTHOUGH IT IS ENTIRELY POSSIBLE THAT
RAFAEL COULD ALREADY BE A HURRICANE BASED ON A CONSENSUS OF THIS
DATA...THE INITIAL INTENSITY IS BEING MAINTAINED AT 60 KT FOR THIS
ADVISORY. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT WILL BE
INVESTIGATING RAFAEL AROUND 1200 UTC...AND DATA FROM THAT MISSION
WILL PROVIDE A BETTER ESTIMATE OF THE ACTUAL INTENSITY.
 
THE INITIAL MOTION ESTIMATE IS 335/09 KT. THERE REMAINS NO
SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING...
AND THE NHC MODEL GUIDANCE REMAINS TIGHTLY CLUSTERED THROUGH THE 72
HOUR FORECAST PERIOD. RAFAEL IS EXPECTED TO TURN NORTHWARD BY THIS
AFTERNOON OR EVENING AS THE RIDGE TO THE NORTH AND NORTHEAST OF THE
CYCLONE WEAKENS DUE TO AN APPROACHING DEEP-LAYER TROUGH CURRENTLY
MOVING THROUGH THE EASTERN UNITED STATES. AS THE TROUGH MOVES OFF
THE U.S. COAST ON TUESDAY...RAFAEL SHOULD TURN NORTHEASTWARD AND
ACCELERATE. AFTER 72 HOURS...THERE IS GREATER SPREAD IN THE
GUIDANCE AS SOME OF THE GLOBAL MODELS SHOW THE EXTRATROPICAL
CYCLONE SLOWING DOWN AS IT INTERACTS WITH A LARGER LOW OVER THE
NORTH ATLANTIC. DESPITE THESE SPEED DIFFERENCES...THE MODELS ARE
IN GOOD AGREEMENT ON THEN EXTRATROPICAL RAFAEL TURNING EASTWARD OVER
THE COLD WATERS OF THE FAR NORTH ATLANTIC AND POSSIBLY BECOME
ABSORBED BY A LARGER EXTRATROPICAL LOW PRESSURE SYSTEM.  THE
OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY
TRACK...AND IS CLOSE TO THE TVCA CONSENSUS MODEL.
 
DESPITE THE 21 KT OF SHEAR ASSESSED BY THE GFS-BASED SHIPS MODEL...
THE UPPER-LEVEL OUTFLOW PATTERN HAS CONTINUED TO EXPAND AND
IMPROVE...ESPECIALLY TO THE EAST WHERE THE OUTFLOW IS BEING
ENHANCED BY A HIGHLY AMPLIFIED UPPER-LEVEL TROUGH LOCATED ALONG 40W
LONGITUDE.  THERE ARE CURRENTLY NO SIGNS THAT THE VERTICAL SHEAR
WILL INCREASE WITHIN THE NEXT 12 HOURS...SO AT LEAST SOME GRADUAL
INTENSIFICATION IS EXPECTED IN THE SHORT TERM. BY DAYS 2-3...
HOWEVER...THE SHEAR IS EXPECTED TO INCREASE TO MORE THAN 30 KT AS
THE U.S. DEEP-LAYER TROUGH APPROACHES RAFAEL...WHICH SHOULD INDUCE
GRADUAL WEAKENING. BY DAY 4...THE GLOBAL MODELS ARE FORECASTING
RAFAEL TO UNDERGO EXTRATROPICAL TRANSITION AS THE CYCLONE INTERACTS
WITH A COLD FRONT. THE INTENSITY FORECAST IS SIMILAR TO THE
PREVIOUS ADVISORY...AND FOLLOWS THE ICON INTENSITY CONSENSUS MODEL.

SPECIAL THANKS TO THE AIR FORCE RESERVE HURRICANE HUNTERS WHO PULLED
DOUBLE DUTY YESTERDAY BY HELPING LOCATE A LIGHT AIRCRAFT AND ITS
PASSENGERS THAT WENT DOWN NEAR THE VIRGIN ISLANDS. WELL DONE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  15/0900Z 22.5N  65.3W   60 KT  70 MPH
 12H  15/1800Z 23.9N  65.7W   65 KT  75 MPH
 24H  16/0600Z 26.3N  65.3W   70 KT  80 MPH
 36H  16/1800Z 29.6N  63.8W   70 KT  80 MPH
 48H  17/0600Z 33.8N  60.9W   65 KT  75 MPH
 72H  18/0600Z 42.6N  50.6W   60 KT  70 MPH
 96H  19/0600Z 48.2N  35.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  20/0600Z 49.3N  24.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 
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