[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 120835
TCDAT2
TROPICAL DEPRESSION TWO DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022009
500 AM AST WED AUG 12 2009

SATELLITE IMAGES INDICATE THAT A PERSISTENT CLUSTER OF THUNDERSTORMS
REMAINS IN THE WESTERN SEMICIRCLE OF THE DEPRESSION...ALTHOUGH
RECENTLY THIS CLUSTER HAS TAKEN ON A SOMEWHAT ELONGATED APPEARANCE.
MICROWAVE AND SHORTWAVE INFRARED DATA SUGGEST THE CENTER REMAINS ON
THE EASTERN SIDE OF THE CONVECTION AND NOT WELL-EMBEDDED WITHIN THE
MAIN CONVECTIVE CLUSTER.  DVORAK ESTIMATES SUGGEST THE MAXIMUM
WINDS ARE NEAR 30 KT...AND THE INITIAL INTENSITY WILL BE HELD AT
THAT VALUE.

THERE IS CONSIDERABLE UNCERTAINTY WITH THE INITIAL POSITION...AND
THE BEST GUESS OF INITIAL MOTION IS 270/10.  GLOBAL MODELS SUGGEST A
GENERAL WESTERLY COURSE IS LIKELY FOR THE NEXT COUPLE OF DAYS AS
RIDGING BUILDS TO THE NORTH OF THE DEPRESSION.  THEREAFTER...A
WEAKNESS IN THE SUBTROPICAL HIGH OVER THE CENTRAL ATLANTIC OCEAN
COULD CAUSE THE TROPICAL CYCLONE TO GAIN SOME LATITUDE.  ALTHOUGH
THE HWRF/BAMD MODELS SHOW A SHARP NORTHWESTWARD MOTION IN THE
LATTER HALF OF THE FORECAST PERIOD...MOST OF THE MODEL GUIDANCE
SUGGEST ONLY A GRADUAL BEND TO A WEST-NORTHWEST TRACK WITH AN
INCREASE IN FORWARD SPEED DUE TO A HIGH BUILDING OVER THE WESTERN
ATLANTIC.  THE OFFICIAL FORECAST IS ADJUSTED SLIGHTLY SOUTHWARD IN
THE FIRST FEW DAYS...BUT ENDS UP VERY CLOSE TO THE PREVIOUS
FORECAST BY THE END OF THE PERIOD.

LIGHT TO MODERATE SOUTHEASTERLY SHEAR IS EXPECTED FOR THE NEXT
SEVERAL DAYS WHILE THE SYSTEM TRAVERSES MARGINALLY WARM WATERS.  IN
GENERAL...THIS ENVIRONMENT WOULD SUPPORT SOME STRENGTHENING...
THOUGH THE PRESENCE OF SOME DRIER/STABLE AIR JUST TO THE NORTH OF
THE DEPRESSION MAY PLAY AN INHIBITING ROLE.  THE STATISTICAL MODELS
SUGGEST THAT THE DEPRESSION COULD BE CLOSE TO HURRICANE STRENGTH IN
A FEW DAYS...WHILE THE DYNAMICAL GUIDANCE SHOWS ONLY A LOW-END
TROPICAL STORM.  THE NHC INTENSITY FORECAST WILL BASICALLY SPLIT
THE DIFFERENCE BETWEEN THOSE OUTCOMES AND REMAINS CLOSE TO THE
PREVIOUS ONE.  IN THE LONGER-TERM...MOST OF THE GLOBAL MODELS
INCREASE THE VERTICAL SHEAR...WHICH SHOULD CAUSE A WEAKENING TREND
WHILE THE SYSTEM IS OVER THE CENTRAL ATLANTIC.

FORECAST POSITIONS AND MAX WINDS

INITIAL      12/0900Z 14.6N  32.4W    30 KT
 12HR VT     12/1800Z 14.6N  34.0W    35 KT
 24HR VT     13/0600Z 14.6N  36.4W    35 KT
 36HR VT     13/1800Z 14.6N  38.9W    40 KT
 48HR VT     14/0600Z 15.0N  41.4W    45 KT
 72HR VT     15/0600Z 16.5N  46.5W    50 KT
 96HR VT     16/0600Z 19.0N  52.5W    45 KT
120HR VT     17/0600Z 22.5N  58.5W    40 KT

$$
FORECASTER BLAKE
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