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| #1152103 (Received by flhurricane at: 10:48 PM 09.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 19 NWS National Hurricane Center Miami FL AL132023 1100 PM AST Sat Sep 09 2023 While the geostationary satellite appearance of Lee has not changed appreciably since the prior advisory, data from a NOAA P-3 reconnaissance mission in the storm, in addition to earlier GPM and SSMIS microwave imagery, indicate that Lee is in the middle of an eyewall replacement cycle (ERC). The aircraft has been reporting both an inner and outer eyewall, with the outer eyewall gradually contracting in size. However, this outer eyewall continues to exhibit some asymmetry, consistent with modest vertical wind shear still affecting the storm. In addition, the aircraft has reported that the inner-core wind field is becoming weaker, but broader, with a more muted wind profile outside of the radius of maximum wind. This observation is also evident comparing TDR data between the morning and evening NOAA-P3 missions. The peak 700 mb flight level winds were down to 94 kt, with SFMR only in the 75-85 kt range. The initial intensity has been adjusted to a somewhat generous 90 kt for this advisory. Lee continues to move west-northwestward this evening at 300/9 kt. As discussed previously, the mid-level ridge axis currently north of Lee is soon expected to shift to its west-southwest, resulting in Lee slowing its forward motion, and perhaps making a slight westward bend over the next 24-36 hours. Afterwards, an eastward-moving mid-latitude trough is expected to erode this ridge and allow Lee to turn northward by the end of the forecast period. There remains a significant amount of spread in both the deterministic and ensemble guidance on when this turn occurs, and then how quickly Lee accelerates northward. For now the NHC track forecast remains closest to the consensus aids, which have slowed a bit from the prior cycle, and the latest track forecast is a bit slower but near the same trajectory as the prior advisory. While vertical wind shear over Lee appears to be gradual decreasing over the system, the ongoing ERC seems to be resulting in the wind field broadening versus allowing Lee to re-intensify so far. However, once this cycle is complete, reintensification is still anticipated, and the NHC intensity forecast still takes Lee back to a category 4 hurricane in 36-48 hours, in good agreement with the latest HAFS-A/B forecasts, which both explicitly show the ongoing ERC. However, Lee`s growing wind field, in combination with its slowing forward motion, could make the hurricane susceptible to feeling the effects of its own cold wake, which the atmospheric-ocean coupled HAFS and HWRF models suggest could begin to occur beyond 36 hours. Thus, the latest NHC intensity forecast shows gradual weakening beginning by that time, with more pronounced weakening by the end of the forecast period as the hurricane traverses already cooled sea-surface temperatures from Franklin and Idalia last week along its forecast track. This intensity forecast is in good agreement with the simple consensus aids, but is a little lower than the HFIP corrected consensus early on. 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 are spreading westward and northward and will affect Puerto Rico, Hispaniola, the Turks and Caicos, the Bahamas, and Bermuda during the next several days. 3. It remains 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, especially 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 tomorrow and continuing into next week as Lee grows in size. Users should continue to monitor updates to the forecast of Lee during the next several days. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 21.0N 59.9W 90 KT 105 MPH 12H 10/1200Z 21.6N 60.9W 100 KT 115 MPH 24H 11/0000Z 22.4N 62.3W 110 KT 125 MPH 36H 11/1200Z 23.0N 63.5W 120 KT 140 MPH 48H 12/0000Z 23.3N 64.7W 115 KT 130 MPH 60H 12/1200Z 23.6N 65.6W 110 KT 125 MPH 72H 13/0000Z 24.0N 66.6W 105 KT 120 MPH 96H 14/0000Z 25.6N 68.0W 95 KT 110 MPH 120H 15/0000Z 28.8N 68.3W 85 KT 100 MPH $$ Forecaster Papin |
