[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 070855
TCDAT4
TROPICAL DEPRESSION NINE DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT SUN AUG 07 2005

NIGHTTIME SATELLITE IMAGERY INDICATES THAT THE CENTER OF TROPICAL
DEPRESSION NINE HAS AGAIN REFORMED TO THE NORTH OF THE PREVIOUS
ADVISORY POSITION.  WHILE THE CYCLONE REMAINS SHEARED...CONVECTION
HAS INCREASED SIGNIFICANTLY NEAR AND EAST OF THE CENTER.  SATELLITE
INTENSITY ESTIMATES ARE NOW 30 KT FROM TAFB AND 25 KT FROM SAB AND
AFWA...SO THE SYSTEM WILL REMAIN A 30 KT DEPRESSION.  HOWEVER...
THE CLOUD PATTERN IS RESEMBLING THAT OF A SHEARED TROPICAL STORM.

THE INITIAL MOTION IS A RATHER UNCERTAIN 295/9.  THE DEPRESSION
REMAINS ON THE SOUTH SIDE OF A LOW/MID-LEVEL RIDGE...WITH A
WEAKNESS IN THE RIDGE LOCATED NEAR AND SOUTHWEST OF TROPICAL STORM
HARVEY.  LARGE-SCALE MODELS SUGGEST SOME WEAKNESS WILL PERSIST IN
THE RIDGE OVER THE WEST-CENTRAL ATLANTIC FOR SEVERAL DAYS...AS A
MID-LEVEL RIDGE NORTHWEST OF THE DEPRESSION MOVES WESTWARD AND A
SECOND RIDGE BUILDS NORTHEAST OF THE DEPRESSION.  THIS PATTERN
SHOULD PRODUCE A WEST-NORTHWESTWARD MOTION FOR THE NEXT 48-72 HR...
FOLLOWED BY A GRADUAL TURN TOWARD THE NORTHWEST OR POSSIBLY NORTH
THEREAFTER.  TRACK GUIDANCE GENERALLY AGREES WITH THIS SCENARIO...
WITH THE NOGAPS AND GFDL CALLING FOR A MORE NORTHERLY MOTION AND
THE GFS A MORE WEST-NORTHWESTERLY MOTION.  THE UKMET TAKES THE
DEPRESSION FARTHER WEST THAN THE OTHER MODELS...BUT IT INITIALIZED
THE SYSTEM TOO FAR SOUTH EVEN BEFORE THE RECENT RE-FORMATION.  THE
LARGE-SCALE MODELS SUGGEST THAT THE DEPRESSION MAY MOVE MORE
WESTWARD FOR THE FIRST 36-48 HR.  THIS IS REFLECTED IN THE NEW
TRACK FORECAST...WHICH EVEN WITH THE MORE NORTHWARD INITIAL
POSITION IS SIMILAR TO THE PREVIOUS FORECAST.  ONE POTENTIAL
PROBLEM WITH THE FORECAST TRACK IS THAT THE CENTER MAY NOT BE
THROUGH RE-FORMING JUST YET.

WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL TROUGH NEAR OR JUST WEST OF
THE DEPRESSION AND LOTS OF MID/UPPER-LEVEL DRY AIR.  THE GFS AND
CANDIAN MODELS FORECAST A SURGE OF UPPER-LEVEL EASTERLIES TO
DEVELOP AND REPLACE THE TROUGH WITH AN ANTICYCLONE.  THE UKMET AND
NOGAPS ARE LESS BULLISH ON THIS POSSIBILITY...AND SO FAR THE WATER
VAPOR IMAGERY SUPPORTS CONTINUED SHEAR.  GIVEN THE INCREASE IN
ORGANIZATION AND GRADUALLY WARMING SE SURFACE TEMPERATURES...SLOW
DEVELOPMENT IS POSSIBLE IN SPITE OF THE SHEAR...AND THIS IS
REFLECTED IN THE INTENSITY FORECAST.  IF THE GFS/CANADIAN
UPPER-LEVEL PATTERN DOES DEVELOP...THE SYSTEM COULD GET MUCH
STRONGER THAN CURRENTLY FORECAST.  IT SHOULD BE NOTED THAT THE GFDL
MODEL...WHICH HAS CONSISTENTLY DISSIPATED THE DEPRESSION...NOW
CALLS FOR IT TO REACH HURRICANE STRENGTH IN ABOUT FOUR DAYS.

FORECASTER BEVEN


FORECAST POSITIONS AND MAX WINDS

INITIAL      07/0900Z 19.6N  44.7W    30 KT
 12HR VT     07/1800Z 20.0N  46.3W    30 KT
 24HR VT     08/0600Z 20.7N  48.4W    35 KT
 36HR VT     08/1800Z 21.4N  50.2W    35 KT
 48HR VT     09/0600Z 22.2N  52.0W    40 KT
 72HR VT     10/0600Z 23.5N  55.0W    45 KT
 96HR VT     11/0600Z 25.5N  57.5W    50 KT
120HR VT     12/0600Z 28.0N  60.0W    55 KT


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