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| #1014757 (Received by flhurricane at: 10:48 PM 31.Aug.2020) TCDAT5 Tropical Depression Fifteen Discussion Number 2 NWS National Hurricane Center Miami FL AL152020 1100 PM EDT Mon Aug 31 2020 Tropical Depression Fifteen is a sheared tropical cyclone, with the edge of the deep convection displaced nearly 30 n mi to the east of the exposed low-level center. An Air Force Reserve Hurricane Hunter mission earlier this evening provided SFMR instrument measurements of nearly 30 kt in the southeast quadrant. And, a recent ASCAT overpass showed several wind vectors in that same general area between 25-30 kt. Therefore, the initial intensity is being held at 30 kt. The depression is moving northeast at 12 kt around the northwestern periphery of the subtropical ridge. A turn to the east-northeast is expected to occur on Tuesday as the cyclone moves along the northern periphery of the ridge. Late in the forecast period, what is left of the cyclone is forecast to get caught in the flow between building high pressure to its northeast, and an approaching trough to its northwest, which should induce a more northerly component of motion. The latest NHC forecast is little changed from the previous one, and is near the tightly clustered track guidance. The cyclone has moved into an environment with moderate westerly shear of about 20 kt, as indicated by the latest UW-CIMSS deep-layer shear analysis product. The SHIPS guidance by both the GFS and ECMWF indicate that the shear magnitude will more than double between 18 h and 36 h from now. So it is anticipated that the only window of time for the depression to strengthen will be tonight through tomorrow, while the system is over warm waters and in a moist atmospheric environment. After 48 h, when the vertical wind shear is forecast to be between 40 and 50 kt, the cyclone is forecast to weaken, and by 96 h the NHC forecast now shows the system degenerating into a remnant low. Exactly what transpires with the cyclone later in the forecast period remains uncertain, as some of the global models suggest that the cyclone will open into a trough in a few days, while others indicate that the system could be absorbed by a larger mid-latitude trough around day 5. Regardless of what occurs by those time frames, the models all suggest that the system should not gain much more strength than it currently has. The official NHC intensity forecast is in good agreement with the various intensity consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 33.2N 75.7W 30 KT 35 MPH 12H 01/1200Z 34.2N 74.0W 35 KT 40 MPH 24H 02/0000Z 35.1N 71.2W 35 KT 40 MPH 36H 02/1200Z 36.0N 68.6W 35 KT 40 MPH 48H 03/0000Z 36.9N 65.9W 35 KT 40 MPH 60H 03/1200Z 37.7N 63.3W 30 KT 35 MPH 72H 04/0000Z 38.1N 60.5W 30 KT 35 MPH 96H 05/0000Z 38.7N 55.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 06/0000Z 41.6N 50.4W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto |