[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 040246
TCDAT5

TROPICAL STORM EMILY DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052011
1100 PM EDT WED AUG 03 2011

EMILY HAS MOVED LITTLE OVER THE LAST SEVERAL HOURS...AS MULTIPLE
FIXES FROM THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT BETWEEN
21Z AND 00Z WERE ALL ESSENTIALLY IN THE SAME LOCATION.  DATA FROM
THE AIRCRAFT SHOWED LITTLE CHANGE IN THE INTENSITY...WHICH REMAINS
45 KT FOR THIS ADVISORY.  THE SLOW MOTION APPEARS TO HAVE ALLOWED
THE LOW-LEVEL CENTER TO COME IN CLOSER PROXIMITY TO THE DEEP
CONVECTION...WHICH HAS EXPANDED WESTWARD OVER THE PAST FEW HOURS.
HOWEVER...THE CIRCULATION SHOULD BECOME SOMEWHAT DISRUPTED BY LAND
INTERACTION WITHIN 24 TO 36 HOURS...SO SLIGHT WEAKENING IS
INDICATED DURING THAT PERIOD.  BEYOND 36 HOURS...GRADUAL
STRENGTHENING IS SHOWN...BUT THE OFFICIAL FORECAST REMAINS A LITTLE
BELOW THE INTENSITY CONSENSUS...AND WELL BELOW THE MORE AGGRESSIVE
GFDL AND HWRF MODELS...GIVEN THE UNCERTAINTY IN THE STRUCTURE OF
EMILY AFTER IT TRAVERSES THE HIGH TERRAIN OF WESTERN HISPANIOLA AND
EASTERN CUBA.

THE INITIAL MOTION ESTIMATE IS VERY SLOW...TOWARD THE WEST OR 280
DEGREES AT 4 KNOTS USING A LONG-TERM AVERAGE...ALTHOUGH THE SHORT
TERM MOTION IS EVEN SLOWER.  THE GUIDANCE IS INSISTENT ON TURNING
EMILY TOWARD THE WEST-NORTHWEST AND NORTHWEST WITH AN INCREASE IN
FORWARD SPEED OVER THE NEXT 24 HOURS OR SO...BUT THE OFFICIAL
FORECAST IS TO THE LEFT OF AND SLOWER THAN MOST OF THE DYNAMICAL
MODELS THROUGH THAT TIME DUE TO THE SLOW INITIAL MOTION.  AFTER 36
HOURS...EMILY SHOULD CONTINUE NORTHWESTWARD AND EVENTUALLY TURN
NORTHWARD INTO A WEAKNESS IN THE SUBTROPICAL RIDGE EAST OF THE
FLORIDA PENINSULA.  THE GUIDANCE CONTINUES TO HAVE RUN TO RUN
CONSISTENCY ISSUES WITH BOTH THE DETAILS OF THE STEERING FEATURES
AND THE STRUCTURE OF THE CYCLONE IN THE MODEL FIELDS.  OVERALL...
THE LATEST ROUND OF GUIDANCE HAS SHIFTED FARTHER TO THE LEFT...AND
THE OFFICIAL FORECAST HAS BEEN NUDGED IN THAT DIRECTION FROM 36 TO
72 HOURS...BUT STILL LIES TO THE EAST OF THE MULTI-MODEL CONSENSUS
AT THOSE TIMES.  BY DAYS 4 AND 5...EMILY SHOULD ACCELERATE QUICKLY
NORTHEASTWARD INTO THE MID-LATITUDE WESTERLIES...AND THE NEW
FORECAST AT THOSE TIMES IS ESSENTIALLY AN UPDATE OF THE PREVIOUS
NHC FORECAST.

THE UNCERTAINTY IN THE TRACK FORECAST CONTINUES TO BE LARGER THAN
NORMAL GIVEN THE CURRENT SLOW MOTION...THE POTENTIAL STRUCTURAL
CHANGES OF THE CYCLONE DUE TO ITS INTERACTION WITH LAND IN THE NEXT
24 TO 36 HOURS...AND THE LACK OF CONSISTENCY IN THE TRACK GUIDANCE
FROM RUN TO RUN.  IF A NORTHWARD COMPONENT OF MOTION DOES NOT BEGIN
SOON...OR THE TRACK GUIDANCE SHIFTS FARTHER TO THE LEFT IN FUTURE
CYCLES...THE THREAT TO FLORIDA AND THE SOUTHEASTERN UNITED STATES
WILL INCREASE.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 17.1N  71.0W   45 KT  50 MPH
 12H  04/1200Z 17.9N  72.9W   45 KT  50 MPH
 24H  05/0000Z 20.0N  74.8W   40 KT  45 MPH
 36H  05/1200Z 22.1N  76.4W   40 KT  45 MPH
 48H  06/0000Z 23.8N  77.4W   45 KT  50 MPH
 72H  07/0000Z 27.0N  79.0W   55 KT  65 MPH
 96H  08/0000Z 31.5N  76.0W   65 KT  75 MPH
120H  09/0000Z 35.0N  69.0W   65 KT  75 MPH

$$
FORECASTER BRENNAN

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