ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM 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 NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:08 UTC