000
WTNT42 KNHC 240858
TCDAT2
 
TROPICAL DEPRESSION SEVENTEEN DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 AM AST SAT SEP 24 2011
 
THE SMALL AREA OF LOW PRESSURE SEVERAL HUNDRED MILES SOUTH OF THE
CAPE VERDE ISLANDS HAS DEVELOPED ENOUGH ORGANIZED CONVECTION TO BE
CONSIDERED A TROPICAL CYCLONE. MICROWAVE DATA FROM TRMM AND AMSR-E
OVER THE PAST FEW HOURS SHOWED DISTINCT CURVED BANDS...AND EARLY
MORNING VISIBLE IMAGES SUGGEST THAT THE CENTER IS WELL EMBEDDED
WITHIN THE CLOUD CANOPY. AN EARLIER ASCAT PASS INDICATED THAT THE
SYSTEM WAS CLOSED...AND HAD WINDS OF ABOUT 30 KT...SO THAT WILL BE
THE INITIAL INTENSITY. ENVIRONMENTAL CONDITIONS APPEAR TO BE
FAVORABLE FOR STRENGTHENING FOR THE NEXT COUPLE OF DAYS WHILE THE
DEPRESSION IS OVER WARM WATERS WITH LIGHT SHEAR. AFTER THAT TIME...
THE CYCLONE COULD WEAKEN SOMEWHAT DUE TO INCREASING SOUTHWESTERLY
SHEAR FROM A LARGE UPPER-LEVEL TROUGH OVER THE CENTRAL ATLANTIC
OCEAN AND DECREASING SSTS. THE NHC INTENSITY FORECAST IS ON THE
CONSERVATIVE SIDE OF THE GUIDANCE ENVELOPE...BUT FOLLOWS THE TREND
OF THE LGEM MODEL.

BEST ESTIMATE OF THE INITIAL MOTION IS 280/12. A MID-LEVEL RIDGE TO
THE NORTH OF THE DEPRESSION IS FORECAST TO WEAKEN...WHICH SHOULD
CAUSE THE CYCLONE TO GRADUALLY TURN TOWARD THE WEST-NORTHWEST AND
NORTHWEST OVER THE NEXT FEW DAYS. SOME OF THE GUIDANCE TURNS THE
SYSTEM MORE TOWARD THE NORTH BY THE END OF THE FORECAST PERIOD DUE
TO A STRONG MID-LATITUDE TROUGH. FOR NOW...MOST OF THE RELIABLE
GLOBAL MODELS SHOW THE TROUGH STAYING FAR ENOUGH AWAY FROM THE
DEPRESSION TO AVOID RECURVATURE...AND THE NHC FORECAST IS ON THE
LEFT SIDE OF THE GUIDANCE ENVELOPE AND NOT TOO FAR FROM THE ECMWF
MODEL.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0900Z 10.7N  25.2W   30 KT  35 MPH
 12H  24/1800Z 11.1N  27.2W   35 KT  40 MPH
 24H  25/0600Z 11.8N  29.3W   40 KT  45 MPH
 36H  25/1800Z 12.7N  31.4W   50 KT  60 MPH
 48H  26/0600Z 13.7N  33.1W   60 KT  70 MPH
 72H  27/0600Z 16.0N  35.5W   60 KT  70 MPH
 96H  28/0600Z 18.0N  37.5W   55 KT  65 MPH
120H  29/0600Z 20.0N  39.5W   50 KT  60 MPH
 
$$
FORECASTER BLAKE