[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 050901
TCDAT4
TROPICAL DEPRESSION NINE DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT FRI AUG 05 2005

THE CENTER OF TD-9 REMAINS DIFFICULT TO LOCATE. THE BEST ESTIMATE OF
THE POSITION IS ABOUT 60 NMI NORTH OF THE PREVIOUS POSITIONS AND
FORECAST TRACKS BASED ON MICROWAVE AND NIGHTIME VISIBLE SATELLITE
IMAGERY. A 05/0411Z AQUA OVERPASS CLEARLY INDICATED THE BROAD
CIRCULATION WAS BETWEEN 14N AND 15N LATITUDE. A MORE SOUTHERLY
POSITION CLOSER TO 14N WAS CHOSEN SINCE THIS WOULD BE CLOSER TO THE
DEEP CONVECTION. HOWEVER...IT IS POSSIBLE THAT THE CENTER MAY HAVE
TO BE ADJUSTED FARTHER NORTH ONCE VISIBLE IMAGERY IS AVAILABLE.

THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 295/11...BASED ON THE
OVERALL MOTION OF THE LARGE CIRCULATION ENVELOPE.  TD-9 IS
CURRENTLY MOVING TOWARD A WEAKNESS IN THE BERMUDA RIDGE THAT IS
BEING CREATED BY AN UPPER-LEVEL LOW NEAR 29N 42W...AND AN
ASSOCIATED TROUGH EXTENDING SOUTHWARD. MOST OF THE GLOBAL MODELS
AGREE THAT THE WEAKNESS WILL SLOWLY FILL IN AS THE LOW WEAKENS...
WHICH WILL ACT TO FORCE THE TROPICAL CYCLONE ON A MORE WESTWARD
TRACK AFTER 36 HOURS. IN THE DAY 4 AND 5 TIME PERIODS...THE MODELS
DIFFER SIGNIFICANTLY WITH THE UKMET...NOGAPS...CANADIAN...AND ECMWF
MODELS TURNING THE CYCLONE NORTHWESTWARD TOWARD ANOTHER DEVELOPING
WEAKNESS IN THE RIDGE...WHEREAS THE GFS AND GFDL MOVE THE STORM
MORE WESTWARD. GIVEN THE HIGH ZONAL FLOW FORECAST TO PERSIST ACROSS
THE U.S. AND NORTH ATLANTIC...THE OFFICIAL FORECAST LEANS MORE
TOWARD THE GFS AND GFDL SOLUTIONS.

ALTHOUGH THE VERTICAL SHEAR IS FORECAST TO REMAIN LOW...LESS THAN 5
KT...THE HIGHER LATITUDE INITIAL POSITION AND FORECAST TRACK KEEPS
THE CYCLONE OVER COOLER SSTS UNTIL 72 HOURS. AFTERWARDS. GRADUALLY
INCREASING SSTS ABOVE 28C SHOULD ALLOW FOR SOME SIGNIFICANT
STRENGTHENING TO OCCUR.ON.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      05/0900Z 14.4N  36.1W    25 KT
 12HR VT     05/1800Z 15.1N  37.5W    30 KT
 24HR VT     06/0600Z 15.9N  39.5W    35 KT
 36HR VT     06/1800Z 16.7N  41.6W    40 KT
 48HR VT     07/0600Z 17.7N  44.4W    45 KT
 72HR VT     08/0600Z 19.0N  48.6W    55 KT
 96HR VT     09/0600Z 20.5N  53.5W    65 KT
120HR VT     10/0600Z 22.0N  58.5W    75 KT


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