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Tropical Depression Eleven Forecast Discussion Number 4
2020-08-12 16:43:00| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Wed Aug 12 2020 000 WTNT41 KNHC 121442 TCDAT1 Tropical Depression Eleven Discussion Number 4 NWS National Hurricane Center Miami FL AL112020 1100 AM AST Wed Aug 12 2020 Satellite imagery indicates that the depression is a little better organized than 24 h ago, with a ragged central convective feature and a curved convective band in the northwestern semicircle. However, recent scatterometer data show this has not yet resulted in strengthening, with 25-30 kt winds occuring to the north of the center. Based on the scatterometer, the initial intensity remains 30 kt. The initial motion remains a little north of due west, or 280/13 kt. There is little change to the forecast philosophy or the forecast track since the last advisory. A westward motion is expected to continue through tonight due to easterly flow on the south side of a strong subtropical ridge situated to the north of the cyclone. After that, the global models forecast a slight weakness to develop within the ridge, allowing the cyclone to turn west-northwestward, with that motion continuing through the end of the forecast period. The new NHC forecast is just to the left of the various consensus models. The southeasterly shear that has so far prevented intensification should diminish in the next 12 h or so, which should allow the cyclone to become a tropical storm. The system should then remain in light to moderate shear through about 48 h, and the intensity forecast calls for a peak intensity of 50 kt during that time. Later in the forecast period, moderate to strong southwesterly shear should develop over the cyclone due to an upper-level trough over the southwestern Atlantic. This shear should cause the system to weaken, and several of the global models forecast it to degenerate to a tropical wave before 120 h. The new intensity forecast will not call for that quick of a demise, but will show weakening due to the shear after 72 h. The new forecast, which has only minor changes from the previous forecast, is near the upper edge of the intensity guidance. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 12.4N 44.2W 30 KT 35 MPH 12H 13/0000Z 12.8N 46.1W 35 KT 40 MPH 24H 13/1200Z 13.5N 48.4W 40 KT 45 MPH 36H 14/0000Z 14.5N 50.8W 45 KT 50 MPH 48H 14/1200Z 15.7N 53.3W 50 KT 60 MPH 60H 15/0000Z 17.0N 55.7W 50 KT 60 MPH 72H 15/1200Z 18.2N 58.1W 50 KT 60 MPH 96H 16/1200Z 20.5N 63.0W 40 KT 45 MPH 120H 17/1200Z 23.5N 66.5W 35 KT 40 MPH $$ Forecaster Beven
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