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Tropical Depression NINE Forecast Discussion Number 5
2015-09-17 16:34:20| National Hurricane Center (Atlantic)
Issued at 1100 AM AST THU SEP 17 2015 000 WTNT44 KNHC 171434 TCDAT4 TROPICAL DEPRESSION NINE DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092015 1100 AM AST THU SEP 17 2015 The center of the depression can be seen in visible imagery exposed to the west of what remains of the deep convection, due to about 25 kt of shear over the cyclone as indicated by UW-CIMSS satellite analyses. The initial intensity remains 30 kt based on the latest Dvorak estimates from TAFB and SAB. The environmental conditions become even less favorable with time, with the shear forecast to continue while the cyclone moves into an increasingly dry environment. These factors should result in slow weakening, and the NHC forecast shows the depression becoming a remnant low by 36 hours, with dissipation expected in 4 to 5 days. The initial position of the depression is a little south of that from the previous advisory, as the partially decoupled low-level circulation is moving northwestward at about 5 kt. The track forecast philosophy has not changed, as the weakening cyclone should move generally northwestward for the next 24 to 36 hours and then turn west-northwestward as a shallower system. The new NHC track is in best agreement with the GFS and shallow BAM and lies south of the multi-model consensus. This forecast is similar to the previous one updated for the initial position and motion. There are a couple of alternate scenarios, however. The depression or its remnants could merge with the disturbance to its east as seen in the UKMET solution or survive as its own entity a little longer as indicated by the latest ECMWF forecast. However, the NHC track forecast continues to favor a solution with a weakening cyclone that remains separate from the disturbance to the east and dissipates by 5 days. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 16.1N 45.2W 30 KT 35 MPH 12H 18/0000Z 16.8N 45.8W 30 KT 35 MPH 24H 18/1200Z 17.8N 46.8W 30 KT 35 MPH 36H 19/0000Z 18.8N 47.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 19/1200Z 19.5N 49.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 20/1200Z 20.5N 51.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 21/1200Z 22.0N 54.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 22/1200Z...DISSIPATED $$ Forecaster Brennan
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