[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 020243
TCDAT5

TROPICAL STORM EMILY DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052011
1100 PM AST MON AUG 01 2011

EMILY STILL HAS A RATHER DISHEVELED APPEARANCE IN GEOSTATIONARY
IMAGERY...AND THE CLOUD TOPS HAVE WARMED A BIT OVER THE PAST FEW
HOURS AND LACK MUCH IN THE WAY OF CURVATURE.  BASED ON THE LACK OF
IMPROVEMENT IN THE SATELLITE PRESENTATION...THE INITIAL INTENSITY
ESTIMATE IS HELD AT 35 KT FOR THIS ADVISORY IN AGREEMENT WITH THE
00Z DVORAK INTENSITY ESTIMATE FROM SAB.  THE ATMOSPHERIC
ENVIRONMENT NEAR AND AHEAD OF THE THE CYCLONE APPEARS TO BE ONLY
MARGINALLY FAVORABLE FOR INTENSIFICATION...AS SEEN BY THE COPIOUS
DRY AIR IN THE 00Z SAN JUAN RADIOSONDE AND SATELLITE PRECIPITABLE
WATER IMAGERY.  THE INTENSITY GUIDANCE SHOWS ONLY MODEST
STRENGTHENING IN THE NEXT 48 HOURS...AND IN FACT THE LATEST GFDL
MODEL RUN EVEN DISSIPATES THE CYCLONE IN ABOUT TWO DAYS.  THE
OFFICIAL FORECAST IS CLOSE TO THE IVCN INTENSITY CONSENSUS THROUGH
36 HOURS...AND THEN SHOWS WEAKENING AT 48 AND 72 HOURS AS EMILY IS
EXPECTED TO INTERACT WITH HISPANIOLA.  ASSUMING THAT EMILY RECOVERS
FROM INTERACTION WITH THE ISLAND...GRADUAL STRENGTHENING IS EXPECTED
LATE IN THE PERIOD AND THE NHC FORECAST IS CLOSE TO THE LGEM.

THE CENTER HAS BEEN A BIT DIFFICULT TO LOCATE SINCE THE AIRCRAFT
DEPARTED...SO THE INITIAL POSITION AND INITIAL MOTION OF 275/15 ARE
QUITE UNCERTAIN AND BASED LARGELY ON CONTINUITY.  OVERALL THE
GLOBAL MODELS ARE IN GOOD AGREEMENT WITH THE EVOLUTION OF THE
SYNOPTIC PATTERN...AS A MID-LEVEL TROUGH DIGGING INTO THE WESTERN
ATLANTIC WILL GRADUALLY ERODE THE RIDGE NORTH OF EMILY OVER THE
NEXT 2 OR 3 DAYS.  THIS WILL ALLOW EMILY TO TURN TOWARD THE
WEST-NORTHWEST AND GRADUALLY SLOW DOWN DURING THIS TIME PERIOD.
LATE IN THE PERIOD... THE MODELS SHOW THE TROUGH LIFTING OUT AND
SOME RIDGING RE-BUILDING NORTH OF EMILY.  HOWEVER...BOTH THE
DETAILS OF THE RIDGE AND THE DEPTH OF THE CYCLONE APPEAR TO MAKE
ALL THE DIFFERENCE IN THE EVENTUAL TRACK.  FOR EXAMPLE...THE LATEST
GFS RUN HAS A SLIGHTLY WEAKER RIDGE AND A MUCH DEEPER
REPRESENTATION OF EMILY THAT MOVES MORE NORTHWARD.  THE HWRF AND
GFS ENSEMBLE MEAN ALSO FOLLOW THIS GENERAL SCENARIO.  ON THE OTHER
HAND...THE ECMWF HAS A MUCH WEAKER REPRESENTATION OF EMILY THAT
MOVES MORE WESTWARD LATE IN THE PERIOD UNDERNEATH A STRONGER RIDGE.
GIVEN THE LARGE MODEL SPREAD...THERE IS SIGNIFICANT UNCERTAINTY IN
THE TRACK FORECAST AT THE END OF THE PERIOD.  THE NEW NHC TRACK
FORECAST IS LARGELY AN UPDATE OF THE PREVIOUS PACKAGE THROUGH 72
HOURS...AND HAS BEEN ADJUSTED A LITTLE TO THE RIGHT TOWARD THE TVCA
MULTI-MODEL CONSENSUS AT DAYS 4 AND 5.


FORECAST POSITIONS AND MAX WINDS

INIT  02/0300Z 15.5N  62.9W   35 KT  40 MPH
 12H  02/1200Z 15.9N  64.9W   40 KT  45 MPH
 24H  03/0000Z 16.8N  67.2W   45 KT  50 MPH
 36H  03/1200Z 17.8N  69.4W   50 KT  60 MPH
 48H  04/0000Z 18.9N  71.4W   45 KT  50 MPH...INLAND
 72H  05/0000Z 22.0N  75.0W   40 KT  45 MPH...OVER WATER
 96H  06/0000Z 25.0N  78.0W   50 KT  60 MPH
120H  07/0000Z 27.5N  80.0W   65 KT  75 MPH

$$
FORECASTER BRENNAN



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