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Tropical Depression Ten Forecast Discussion Number 4
2021-08-29 04:35:53| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sat Aug 28 2021 941 WTNT45 KNHC 290235 TCDAT5 Tropical Depression Ten Discussion Number 4 NWS National Hurricane Center Miami FL AL102021 1100 PM AST Sat Aug 28 2021 The center of the tropical depression remained exposed for much of the evening, though in the past hour or so the center has become located closer to a small, ragged area of convection. A more pronounced curved band can also be seen east of the depression though this feature is located over 120 n mi away. This structure is due to ongoing west-southwesterly shear and the presence of some dry air that continues to plague the cyclone. The latest Dvorak intensity estimate from TAFB and wind data from a recent ASCAT-B overpass indicate the initial intensity remains 30 kt. Some slight strengthening is possible later tonight through Sunday morning as a slight decrease in shear combined with the diurnal convective maximum may allow the depression to become a tropical storm. Thereafter through 60 h, the shear is forecast to increase, while the system moves into an drier environment. Thus, no further strengthening is forecast during this period, and the cyclone could weaken back into a tropical depression. By around 72 h, global models are suggesting that the shear will decrease again. So, some gradual strengthening is forecast after that time. It should also be noted that the GFS, which earlier forecast the system to degenerate into a remnant low in a few days, now keeps the cyclone in tact and deepens it when the shear lessens toward the end of the 5-day forecast period. The latest NHC intensity forecast is close to the previous one through 24 h, but is higher beyond 24 h. This forecast is a blend of the SHIPS and IVCN guidance through 72 h, but is lower than those solutions after that time. The depression is moving toward the north at 9 kt toward a weakness in the subtropical ridge, carved out by a mid- to upper-level trough over the north-central Atlantic. This trough and associated ridge weakness is forecast to remain in place for the next few days, resulting in the cyclone continuing a general northward motion. By late in the forecast period, the trough is expected to lift out of the region and be replaced by a ridge, which would result in the system turning northwestward. The latest NHC track forecast is little changed from the previous one and lies near the various multi-model consensus tracks. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 16.6N 49.9W 30 KT 35 MPH 12H 29/1200Z 17.7N 49.9W 35 KT 40 MPH 24H 30/0000Z 19.4N 49.9W 35 KT 40 MPH 36H 30/1200Z 20.8N 49.7W 35 KT 40 MPH 48H 31/0000Z 22.3N 49.2W 35 KT 40 MPH 60H 31/1200Z 23.5N 49.0W 35 KT 40 MPH 72H 01/0000Z 25.0N 49.2W 40 KT 45 MPH 96H 02/0000Z 28.2N 50.6W 40 KT 45 MPH 120H 03/0000Z 31.5N 51.7W 45 KT 50 MPH $$ Forecaster Latto
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