ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM Tropical Storm Lee Discussion Number 4 NWS National Hurricane Center Miami FL AL132023 500 AM AST Wed Sep 06 2023 Lee continues to strengthen at a quick pace. Satellite images show that deep convection has been increasing in intensity and coverage in a central dense overcast feature and in a sprawling curved band over the western semicircle. The Dvorak classifications from TAFB and SAB are now 3.5/55 kt, and accordingly, the initial intensity has been increased to 55 kt. Lee is not far from hurricane strength, and it likely will achieve that status later today. The tropical storm is moving west-northwestward at 14 kt on the south side of a subtropical ridge over the central Atlantic. This ridge is expected to persist to the north of Lee during the next several days, keeping the storm on a west-northwest track through the remainder of the week and over the weekend. Although the NHC forecast and the model guidance continue to show Lee passing to the north of the northern Leeward Islands this weekend, users are reminded that the details of the track forecast are still uncertain at those time ranges. For reference, the average NHC forecast track errors are around 125 and 175 n mi on days 4 and 5, respectively. The NHC track forecast lies on the southern side of the model guidance envelope, roughly halfway between the usually most skillful consensus aids, HCCA and TVCA. Lee has already been strengthening fairly quickly despite some east-northeasterly vertical wind shear over the system. Since the shear is expected to relax while the storm remains over very warm water and in a moist environment, continued steady to rapid intensification is expected during the next few days. Most of the intensity models are very aggressive, bringing Lee to major hurricane status by the weekend, but they don't show much change in strength in the short term. In addition, even the global models like the GFS and ECMWF show explosive intensification and forecast Lee's minimum pressure to drop by more than 60 mb by the end of the forecast period. The NHC intensity forecast lies near the high end of the model guidance during the next 24-48 hours, but falls to near the middle of the guidance envelope after that. Regardless of the details, there is high confidence that Lee will be a powerful hurricane late this week and over the weekend. KEY MESSAGES: 1. Lee is forecast to become a major hurricane by late this week and could bring impacts to the Leeward Islands this weekend. While it is too soon to determine the location and magnitude of these possible impacts, interests in this area should monitor the progress of Lee and further updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 13.7N 44.6W 55 KT 65 MPH 12H 06/1800Z 14.3N 46.4W 70 KT 80 MPH 24H 07/0600Z 15.1N 48.8W 80 KT 90 MPH 36H 07/1800Z 16.0N 51.3W 90 KT 105 MPH 48H 08/0600Z 17.0N 53.7W 105 KT 120 MPH 60H 08/1800Z 18.1N 56.2W 120 KT 140 MPH 72H 09/0600Z 19.2N 58.4W 130 KT 150 MPH 96H 10/0600Z 21.1N 62.4W 130 KT 150 MPH 120H 11/0600Z 22.7N 65.5W 130 KT 150 MPH $$ Forecaster Cangialosi NNNN