1WTNT42 KNHC 240858
2TCDAT2
3
4TROPICAL DEPRESSION SEVENTEEN DISCUSSION NUMBER   1
5NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
6500 AM AST SAT SEP 24 2011
7
8THE SMALL AREA OF LOW PRESSURE SEVERAL HUNDRED MILES SOUTH OF THE
9CAPE VERDE ISLANDS HAS DEVELOPED ENOUGH ORGANIZED CONVECTION TO BE
10CONSIDERED A TROPICAL CYCLONE. MICROWAVE DATA FROM TRMM AND AMSR-E
11OVER THE PAST FEW HOURS SHOWED DISTINCT CURVED BANDS...AND EARLY
12MORNING VISIBLE IMAGES SUGGEST THAT THE CENTER IS WELL EMBEDDED
13WITHIN THE CLOUD CANOPY. AN EARLIER ASCAT PASS INDICATED THAT THE
14SYSTEM WAS CLOSED...AND HAD WINDS OF ABOUT 30 KT...SO THAT WILL BE
15THE INITIAL INTENSITY. ENVIRONMENTAL CONDITIONS APPEAR TO BE
16FAVORABLE FOR STRENGTHENING FOR THE NEXT COUPLE OF DAYS WHILE THE
17DEPRESSION IS OVER WARM WATERS WITH LIGHT SHEAR. AFTER THAT TIME...
18THE CYCLONE COULD WEAKEN SOMEWHAT DUE TO INCREASING SOUTHWESTERLY
19SHEAR FROM A LARGE UPPER-LEVEL TROUGH OVER THE CENTRAL ATLANTIC
20OCEAN AND DECREASING SSTS. THE NHC INTENSITY FORECAST IS ON THE
21CONSERVATIVE SIDE OF THE GUIDANCE ENVELOPE...BUT FOLLOWS THE TREND
22OF THE LGEM MODEL.
23
24BEST ESTIMATE OF THE INITIAL MOTION IS 280/12. A MID-LEVEL RIDGE TO
25THE NORTH OF THE DEPRESSION IS FORECAST TO WEAKEN...WHICH SHOULD
26CAUSE THE CYCLONE TO GRADUALLY TURN TOWARD THE WEST-NORTHWEST AND
27NORTHWEST OVER THE NEXT FEW DAYS. SOME OF THE GUIDANCE TURNS THE
28SYSTEM MORE TOWARD THE NORTH BY THE END OF THE FORECAST PERIOD DUE
29TO A STRONG MID-LATITUDE TROUGH. FOR NOW...MOST OF THE RELIABLE
30GLOBAL MODELS SHOW THE TROUGH STAYING FAR ENOUGH AWAY FROM THE
31DEPRESSION TO AVOID RECURVATURE...AND THE NHC FORECAST IS ON THE
32LEFT SIDE OF THE GUIDANCE ENVELOPE AND NOT TOO FAR FROM THE ECMWF
33MODEL.
34
35
36FORECAST POSITIONS AND MAX WINDS
37
38INIT  24/0900Z 10.7N  25.2W   30 KT  35 MPH
39 12H  24/1800Z 11.1N  27.2W   35 KT  40 MPH
40 24H  25/0600Z 11.8N  29.3W   40 KT  45 MPH
41 36H  25/1800Z 12.7N  31.4W   50 KT  60 MPH
42 48H  26/0600Z 13.7N  33.1W   60 KT  70 MPH
43 72H  27/0600Z 16.0N  35.5W   60 KT  70 MPH
44 96H  28/0600Z 18.0N  37.5W   55 KT  65 MPH
45120H  29/0600Z 20.0N  39.5W   50 KT  60 MPH
46
47$$
48FORECASTER BLAKE
49
50
51WTNT42 KNHC 241458
52TCDAT2
53
54TROPICAL DEPRESSION SEVENTEEN DISCUSSION NUMBER   2
55NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
561100 AM EDT SAT SEP 24 2011
57
58AFTER AN EARLIER INCREASE IN DEEP CONVECTION AND BANDING
59FEATURES...THE CONVECTIVE ORGANIZATION OF THE DEPRESSION HAS
60DECREASED A LITTLE SINCE THE 12Z FIXES. INTENSITY ESTIMATES ARE
61T2.8/41 KT FROM UW-CIMSS ADT...T2.5/35 KT FROM TAFB...AND T1.5/25
62KT FROM SAB. HOWEVER...THE CURVED BAND TO THE NORTH OF CENTER HAS
63FRACTURED AND DEGENERATED AND THE ADT ESTIMATES ARE BASED ON AN
64UNREPRESENTATIVE SHEAR PATTERN. AS A RESULT...THE INITIAL INTENSITY
65WILL REMAIN AT 30 KT FOR THIS ADVISORY...WHICH IS CONSISTENT WITH
66SEVERAL 30-KT WIND VECTORS NOTED IN A 1058Z ASCAT OVERPASS.
67
68THE INITIAL MOTION ESTIMATE IS 285/14. THE CYCLONE IS EXPECTED TO
69MOVE IN A GENERAL WEST-NORTHWESTWARD MOTION FOR THE NEXT 3 DAYS OR
70SO UNDER THE INFLUENCE OF A STRONG SUBTROPICAL RIDGE ORIENTED
71EAST-WEST ALONG 20N LATITUDE. HOWEVER...BY 72 HOURS A BREAK IN THE
72RIDGE IS FORECAST TO DEVELOP BETWEEN 40-45W LONGITUDE AS A BROAD
73LOW PRESSURE TROUGH DIGS SOUTHEASTWARD OVER THE EASTERN ATLANTIC.
74THIS SHOULD RESULT IN THE CYCLONE SLOWING DOWN AND TURNING TOWARD
75THE NORTHWEST INTO THE WEAKNESS. THE OFFICIAL FORECAST IS JUST AN
76EXTENSION OF THE PREVIOUS ADVISORY TRACK AND LIES CLOSE TO THE
77CONSENSUS MODELS TVCN AND TVCA.
78
79ENVIRONMENTAL CONDITIONS WILL BE MAXIMIZED DURING THE NEXT 48 HOURS
80OR SO FOR INTENSIFICATION TO OCCUR OVER THE NEXT COUPLE OF DAYS.
81AFTER THAT...VERTICAL SHEAR IS EXPECTED TO INCREASE...ALBEIT TO
82ONLY ABOUT 15 KT...FROM THE SOUTHWEST AHEAD OF THE AFOREMENTIONED
83MID/UPPER-LEVEL TROUGH. THIS IS EXPECTED TO RESULT IN A SLOWER RATE
84OF INTENSIFICATION.  THE OFFICIAL INTENSITY FORECAST REMAINS ON THE
85CONSERVATIVE SIDE OF THE INTENSITY GUIDANCE ENVELOPE AND FOLLOWS A
86BLEND OF THE SHIPS AND LGEM MODELS.
87
88FORECAST POSITIONS AND MAX WINDS
89
90INIT  24/1500Z 11.0N  26.7W   30 KT  35 MPH
91 12H  25/0000Z 11.4N  28.3W   35 KT  40 MPH
92 24H  25/1200Z 12.2N  30.5W   40 KT  45 MPH
93 36H  26/0000Z 13.2N  32.3W   50 KT  60 MPH
94 48H  26/1200Z 14.2N  33.8W   60 KT  70 MPH
95 72H  27/1200Z 16.4N  36.1W   60 KT  70 MPH
96 96H  28/1200Z 18.4N  38.1W   55 KT  65 MPH
97120H  29/1200Z 20.5N  39.5W   50 KT  60 MPH
98
99$$
100FORECASTER STEWART
101
102
103