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Tropical Depression NINE Forecast Discussion Number 6
2015-09-17 22:34:54| National Hurricane Center (Atlantic)
Issued at 500 PM AST THU SEP 17 2015 000 WTNT44 KNHC 172034 TCDAT4 TROPICAL DEPRESSION NINE DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092015 500 PM AST THU SEP 17 2015 The depression remains poorly organized, with the center still exposed to the west of the deep convection. A few bursts of convection have been trying to redevelop closer to the center, but the 20 to 25 kt of shear is keeping the convection more than a degree from the center. The initial intensity has been lowered to 25 kt based on ASCAT data from earlier today. The depression should continue to slowly spin down due to shear and dry air in the mid and upper levels. The cyclone is forecast to become a remnant low in 24 to 36 hours, although timing when deep convection will dissipate is highly uncertain. The low-level circulation is forecast to dissipate in 4 to 5 days, in best agreement with the latest GFS forecast. The motion of the center has been slow and erratic today, with an has initial motion estimate of 005/03 reflecting a jog to the right during the past few hours. All of the guidance, even the shallow BAM, is insistent on a turn back toward the northwest in the next 12 to 24 hours, and that is reflected in the NHC track forecast. Through 24 hours the NHC track is on the right side of the guidance to account for the initial motion. After that time, a gradual bend toward the west-northwest is forecast as the shallow system becomes steered by the low-level flow. Later in the period the NHC track is close to the previous one adjusted for the initial position and motion and is near the shallow BAMS and the GFS. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 16.5N 44.8W 25 KT 30 MPH 12H 18/0600Z 17.2N 45.5W 25 KT 30 MPH 24H 18/1800Z 18.2N 46.6W 25 KT 30 MPH 36H 19/0600Z 19.0N 47.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 19/1800Z 19.7N 49.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 20/1800Z 20.7N 51.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 21/1800Z 22.0N 54.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 22/1800Z...DISSIPATED $$ Forecaster Brennan
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