Tropical Depression SEVEN

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TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072009
500 PM AST MON SEP 07 2009
 
SATELLITE IMAGES INDICATE THAT THE BROAD LOW PRESSURE AREA LOCATED
SOUTH OF THE CAPE VERDE ISLANDS HAS ACQUIRED ENOUGH ORGANIZATION TO
BE CLASSIFIED AS A TROPICAL DEPRESSION...THE SEVENTH OF THE 2009
ATLANTIC HURRICANE SEASON. THE EXACT CENTER OF THE DEPRESSION IS
SOMEWHAT DIFFICULT TO LOCATE. EARLIER TODAY THE LOW-LEVEL CENTER
APPEARED TO BE NEAR THE EASTERN EDGE OF THE DEEP CONVECTION.
HOWEVER NOW THE THE CENTER APPEARS TO BE UNDER THE DEEP CONVECTION
...BUT DISPLACED EAST OF THE MID-LEVEL CENTER SEEN IN SATELLITE
IMAGERY. DESPITE A LARGE SPREAD IN THE SATELLITE POSITION ESTIMATES
FROM TAFB AND SAB...BOTH CLASSIFICATIONS WERE T2.0...YIELDING AN
INITIAL INTENSITY OF 30 KT.
 
THE HIGHLY UNCERTAIN INITIAL MOTION ESTIMATE IS 280/14. THE
DEPRESSION IS CURRENTLY LOCATED SOUTH OF A NARROW EAST-TO-WEST
ORIENTED RIDGE. THE RIDGE IS FORECAST TO WEAKEN AS A MID-LEVEL
TROUGH MOVES INTO THE EASTERN ATLANTIC AND AN UPPER-LEVEL LOW
CUTS-OFF NEAR 27N40W DURING THE NEXT DAY OR TWO. THIS IS EXPECTED
TO ALLOW THE CYCLONE TO TURN NORTHWESTWARD IN A COUPLE OF DAYS...
FOLLOWED BY A TURN TO THE NORTH THEREAFTER. THE TRACK GUIDANCE IS IN
REASONABLY GOOD AGREEMENT ON THIS SOLUTION...AND THE OFFICIAL
FORECAST IS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
 
THE DEPRESSION IS CURRENTLY WITHIN AN AREA OF MODERATE EASTERLY
VERTICAL SHEAR...BUT THE SHEAR IS FORECAST TO ABATE WITHIN THE NEXT
DAY OR SO. SEA SURFACE TEMPERATURES ARE WARM ALONG THE FORECAST
TRACK AND THE DEPRESSION IS EXPECTED TO GRADUALLY STRENGTHEN DURING
THE NEXT COUPLE OF DAYS. THEREAFTER...INCREASING SOUTHERLY TO
SOUTHWESTERLY SHEAR IS FORECAST TO HALT FURTHER INTENSIFICATION.
THE NHC FORECAST IS CLOSEST TO THE LGEM GUIDANCE...WHICH TYPICALLY
ACCOUNTS FOR INCREASING SHEAR IN THE LONGER RANGES MORE ACCURATELY.
THE OFFICIAL FORECAST IS LOWER THAN THE HWRF AND SHIPS GUIDANCE...
WHICH BOTH BRING THE CYCLONE TO NEAR HURRICANE STRENGTH IN 2-3 DAYS.
 
THE CENTER OF THE DEPRESSION IS FORECAST TO PASS WELL SOUTHWEST OF
THE SOUTHERNMOST CAPE VERDE ISLANDS TONIGHT. OUTER RAIN BANDS ARE
LIKELY TO CONTINUE TO SPREAD ACROSS THE ISLANDS...PRODUCING LOCALLY
HEAVY RAIN AND GUSTY WINDS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/2100Z 12.5N  24.5W    30 KT
 12HR VT     08/0600Z 12.6N  26.5W    35 KT
 24HR VT     08/1800Z 13.0N  28.7W    45 KT
 36HR VT     09/0600Z 13.9N  30.5W    50 KT
 48HR VT     09/1800Z 15.1N  32.1W    55 KT
 72HR VT     10/1800Z 17.6N  33.9W    55 KT
 96HR VT     11/1800Z 19.5N  34.5W    50 KT
120HR VT     12/1800Z 21.0N  34.5W    45 KT
 
$$
FORECASTER BROWN
 
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