000 WTNT45 KNHC 161457 TCDAT5 Tropical Depression Fifteen Discussion Number 5 NWS National Hurricane Center Miami FL AL152023 1100 AM AST Sat Sep 16 2023 The tropical depression has not changed much this morning. The center remains poorly defined, and visible satellite imagery indicates a broad region of low- and mid-level rotation persisting over a large area. Most of the deep convection is occurring in the northern semicircle of the broad circulation. Subjective Dvorak estimates from SAB and TAFB were 25 kt and 35 kt, respectively, and are similar to the objective Dvorak estimates. Based on the disorganized structure and the current intensity estimates, the intensity is held at 30 kt for this advisory. A late arriving ASCAT pass suggests that this estimate may be a bit generous. Since the center of circulation is broad, the initial motion is somewhat uncertain and estimated at 330/16 kt. This general motion is expected to continue for the next couple days as the depression moves along the southern periphery of a mid-level ridge located to the northeast of the system. Track guidance, including global and regional hurricane models, is in general agreement that the system will continue on a northwestward trajectory for the next several days. After 72 hours, the track forecast uncertainty increases somewhat as the system will begin to interact with a deep-layer trough. This trough interaction is expected to induce a more poleward shift in the track and eventually recurve the system toward the northeast by 120 hours. The NHC track forecast is similar to the prior forecast and in agreement with the consensus aids, TVCN and HCCA. The system is currently in a favorable environment for intensification, with low vertical wind shear and warm sea surface temperatures expected to persist during the next several days. However, the timing of intensification will depend on how quickly the system is able to consolidate into a more compact structure. The current intensity forecast assumes that it will take 24-36 hours for this to happen, with the system expected to become a hurricane in 48 hours. The current forecast reaches 95 kt by 72 h, although some of the regional hurricane models, including HWRF and HMON, indicate a more rapid intensification. ECMWF-SHIPS guidance continues to indicate a greater than a 40 percent chance of rapid intensification in the next 72 hours. By mid-week, as the system recurves to the northeast, it is expected to gradually weaken as southwesterly shear increases. The NHC forecast is lower than the regional model guidance and is similar to both the prior forecast and HCCA. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 19.7N 46.2W 30 KT 35 MPH 12H 17/0000Z 21.3N 47.4W 35 KT 40 MPH 24H 17/1200Z 23.2N 49.0W 45 KT 50 MPH 36H 18/0000Z 24.7N 50.4W 55 KT 65 MPH 48H 18/1200Z 26.2N 52.2W 65 KT 75 MPH 60H 19/0000Z 27.5N 54.1W 75 KT 85 MPH 72H 19/1200Z 28.9N 56.0W 95 KT 110 MPH 96H 20/1200Z 32.8N 58.3W 90 KT 105 MPH 120H 21/1200Z 37.0N 55.2W 80 KT 90 MPH $$ Forecaster Hogsett/Bucci