ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM Hurricane Lee Discussion Number 15 NWS National Hurricane Center Miami FL AL132023 1100 PM AST Fri Sep 08 2023 Strong southwesterly shear has taken a toll on Lee's structure. The crews of ongoing NOAA and Air Force Reserve Hurricane Hunter missions reported that the hurricane's eyewall has opened up, and the satellite presentation has degraded significantly since earlier today. Both planes have found the minimum pressure rising during their missions, with the latest measurements being around 963 mb. Based on this pressure and the planes' wind measurements, Lee's initial intensity is set at 100 kt. Moderate-to-strong deep-layer southwesterly shear is expected to continue for at least the next 24 hours, if not longer. The GFS model is the quickest to show the shear abating, but the ECMWF now maintains shear over Lee for much of the forecast period. Most of the intensity guidance shows Lee weakening further during the next 12-24 hours while the shear is at its strongest, and that is shown in the new NHC forecast. Despite the uncertainty in how the upper-level pattern, and hence the shear profile, will evolve around Lee, it is assumed that the atmospheric environment will become at least a little more conducive for restrengthening after 24 hours. The NHC intensity forecast blends the latest IVCN and HCCA consensus models with the previous official forecast, particularly after 48 hours. Confidence in the intensity forecast is low at the moment, although it is likely that Lee will remain a dangerous hurricane for at least the next 5 days. Lee's heading and speed remain 300 degrees at 11 kt. The mid-tropospheric ridge to the north of the hurricane is forecast to build to the west and southwest during the next few days, which will keep Lee on a west-northwestward course with a decrease in speed through next Tuesday. By Wednesday, a deep-layer trough is forecast to amplify over the eastern United States, erode the ridge, and cause Lee to gradually turn toward the northwest. Although the track models agree on this general scenario, there is disagreement on how far west Lee will get before it makes the turn. To account for the latest suite of models, the NHC track forecast has been shifted slightly westward on days 3 through 5, close to the consensus aids but not as far west as the ECMWF, UKMET, and the GEFS ensemble mean. KEY MESSAGES: 1. Lee's core is expected to move well north of the northern Leeward Islands, the Virgin Islands, and Puerto Rico this weekend and early next week. 2. Dangerous surf and life-threatening rip currents are affecting portions of the northern Leeward Islands. These conditions will spread westward and northward, affecting Puerto Rico, Hispaniola, the Turks and Caicos, the Bahamas, and Bermuda through the weekend. 3. It is way too soon to know what level of impacts, if any, Lee might have along the U.S. East Coast, Atlantic Canada, or Bermuda late next week, particularly since the hurricane is expected to slow down considerably over the southwestern Atlantic. Regardless, dangerous surf and rip currents are expected along most of the U.S. East Coast beginning Sunday and Monday. Continue to monitor updates to Lee's forecast during the next several days. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 19.3N 56.5W 100 KT 115 MPH 12H 09/1200Z 20.0N 57.8W 95 KT 110 MPH 24H 10/0000Z 20.8N 59.4W 95 KT 110 MPH 36H 10/1200Z 21.5N 60.8W 105 KT 120 MPH 48H 11/0000Z 22.0N 62.0W 115 KT 130 MPH 60H 11/1200Z 22.5N 63.2W 120 KT 140 MPH 72H 12/0000Z 22.8N 64.2W 120 KT 140 MPH 96H 13/0000Z 23.5N 66.4W 120 KT 140 MPH 120H 14/0000Z 25.3N 67.7W 105 KT 120 MPH $$ Forecaster Berg NNNN