ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM Hurricane Lee Discussion Number 7 NWS National Hurricane Center Miami FL AL132023 1100 PM AST Wed Sep 06 2023 Lee has an asymmetric structure this evening, with the bulk of the convective activity located to the east of the center. Dvorak estimates from TAFB and SAB were a pair of T4.0s/65 kt, but objective Dvorak estimates from UW-CIMSS are a little higher. Therefore, Lee's initial intensity is set at 70 kt. The initial motion remains west-northwestward, or 295/12 kt, with Lee situated to the south of the subtropical ridge. Ridging is expected to build westward, and even out ahead of the hurricane over the southwestern Atlantic, during the next 5 days. As a result, Lee is likely to maintain a west-northwestward trajectory but gradually slow down beyond day 2, with its forward speed decreasing to about 7 kt by day 5. The new NHC track forecast is right on top of the previous prediction during the first 3 days of the forecast. After that, the official forecast has been nudged westward, leaning toward the latest TVCX and HCCA consensus aids. The track model envelope continues to indicate that the core of Lee will pass to the north of the northern Leeward Islands. However, interests in those islands should continue to monitor Lee's forecasts as the typical three-day NHC track error is about 90 n mi, and the northernmost Leeward Islands currently have a 1-in-4 chance of experiencing sustained tropical-storm-force winds on the southern side of the storm. Global model fields show a well-defined upper-level anticyclone developing over Lee during the next 24 hours and persisting over the hurricane into the weekend, which should keep the deep-layer shear quite low. In addition, oceanic heat content values will double along Lee's track during the next 3 days. As a result, rapid intensification (RI) is forecast to begin on Thursday, and following the previous forecast, a 65-kt increase in strength is predicted during the next 3 days, bringing Lee to high-end category 4 intensity. This forecast lies close to the HAFS dynamical model and HCCA consensus aid solutions, and it is also supported by very high RI probabilities from the DTOPS scheme for the 36-, 48-, and 72-hour forecast periods. Fluctuations in intensity are likely by days 4 and 5 due to potential eyewall replacements, but Lee is still expected to be a large and dangerous hurricane over the southwestern Atlantic early next week. KEY MESSAGES: 1. Lee is forecast to become a major hurricane by early Friday, with its core moving north of the northern Leeward Islands, the Virgin Islands, and Puerto Rico this weekend into early next week. There is the potential for tropical storm conditions to occur on some of these islands over the weekend, and interests there should monitor future updates to Lee's forecast. 2. Swells generated by Lee are expected to reach portions of the Lesser Antilles on Friday, and the British and U.S. Virgin Islands, Puerto Rico, Hispaniola, the Bahamas, and Bermuda this weekend. These swells are likely to cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 15.4N 47.7W 70 KT 80 MPH 12H 07/1200Z 16.1N 49.5W 75 KT 85 MPH 24H 08/0000Z 17.0N 51.9W 85 KT 100 MPH 36H 08/1200Z 18.1N 54.2W 105 KT 120 MPH 48H 09/0000Z 19.1N 56.5W 120 KT 140 MPH 60H 09/1200Z 20.1N 58.5W 130 KT 150 MPH 72H 10/0000Z 20.8N 60.3W 135 KT 155 MPH 96H 11/0000Z 22.0N 63.5W 130 KT 150 MPH 120H 12/0000Z 23.0N 66.1W 125 KT 145 MPH $$ Forecaster Berg NNNN