ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM Tropical Storm Lee Discussion Number 5 NWS National Hurricane Center Miami FL AL132023 1100 AM AST Wed Sep 06 2023 Recent geostationary and microwave satellite imagery shows that the convective structure of Lee continues to improve. Visible imagery shows a well-defined curved band of convection that wraps around the eastern portion of the circulation, and a couple of earlier microwave images revealed a ragged mid-level eye that was open to the north. The low-level structure noted in the 1156 UTC GMI microwave overpass was quite organized with a well-defined low-level eye feature. The latest subjective Dvorak T-numbers from SAB and TAFB were T3.5 (55 kt), but given the continued increase in structure the initial intensity has been raised to 60 kt. Lee is moving west-northwestward at about 12 kt to the south side of a low- to mid-level ridge over the central Atlantic. The ridge is forecast to remain intact for the next several days and a west-northwestward motion at around the same forward speed is expected through the weekend. The track guidance continues to show that the core of Lee will pass to the north of the northern Leeward Islands, however interests in those islands should continue to monitor the latest forecasts as the typical three- and four-day NHC track errors are about 90 and 125 n mi, respectively. The NHC track forecast is again along the southern side of the guidance envelope, between the faster and farther south HFIP corrected consensus model, and the TVCA multi-model consensus aid. Despite the continued increase in organization there appears to be some east-northeasterly shear over Lee. The shear is forecast to relax within the next 24 hours, and given the well-organized low-level structure of the cyclone, steady to rapid strengthening appears likely as Lee traverses SSTs of 29-30C during the next few days. The NHC intensity forecast is similar to the previous advisory, bringing Lee to hurricane strength very soon, and to a major hurricane within 48 hours. Continued strengthen seems likely after that time, but hard-to-predict eyewall replacement cycles could cause some fluctuations in intensity later in the weekend and early next week. The NHC intensity forecast is near the upper-end of the guidance and calls for Lee to reach category 4 intensity in two to three days. KEY MESSAGES: 1. Lee is forecast to become a major hurricane by early Saturday and could bring impacts to the northern 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. 2. Swells generated by Lee are expected to reach portions of the Lesser Antilles on Friday. These swells are likely to cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 14.1N 45.5W 60 KT 70 MPH 12H 07/0000Z 14.8N 47.3W 75 KT 85 MPH 24H 07/1200Z 15.7N 49.6W 85 KT 100 MPH 36H 08/0000Z 16.6N 52.2W 95 KT 110 MPH 48H 08/1200Z 17.6N 54.7W 105 KT 120 MPH 60H 09/0000Z 18.7N 56.9W 120 KT 140 MPH 72H 09/1200Z 19.8N 59.2W 130 KT 150 MPH 96H 10/1200Z 21.5N 62.8W 130 KT 150 MPH 120H 11/1200Z 22.9N 65.7W 130 KT 150 MPH $$ Forecaster Brown NNNN