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| #1152249 (Received by flhurricane at: 11:06 PM 10.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 23 NWS National Hurricane Center Miami FL AL132023 1100 PM AST Sun Sep 10 2023 There has been a wealth of data to dig though this evening for Hurricane Lee. Observations from both satellite imagery and this evening`s NOAA-P3 mission indicate the hurricane has become more symmetric in both its convective pattern and wind field. On satellite, Lee has once again become more impressive with a warming eye surrounded by cold -65 to -75C eyewall cloud tops. In response, the subjective Dvorak estimates have been increasing, both T6.0/115 kt from TAFB and SAB. In addition, a single closed eyewall of 25 n mi in diameter was reported by the NOAA aircraft, which has also been observed by the TDR data and an earlier 2151 UTC SSMIS microwave pass. The surface pressure has also been dropping, with the most recent dropsonde in the eye reporting 950 mb. However, the winds have yet to respond to the decreasing pressure, with peak flight-level winds of 108 kt, SFMR at 103 kt, and surface reduced TDR data also in the 100-105 kt range. All of the in-situ aircraft data supports maintaining an initial intensity of 105 kt this advisory. A Synthetic Aperture Radar (SAR) pass valid at 2213 UTC also showed a 105-kt peak wind, but with expanding 64-kt wind radii, which might explain why the winds have yet to respond to the pressure drop. Track-wise, Lee continues to move west-northwestward, at 305/6 kt. This motion is expected to generally continue with a further slowdown in the forward motion now that the mid-level ridging influencing the storms steering has shifted more northwest in front of the hurricane. However, this ridge is expected to then become eroded by an approaching deep-layer trough, allowing Lee to turn northward into the weakness produced by the trough. The track guidance this cycle is in fairly good agreement over the next 5 days, with the largest details still related to the forward motion of Lee after it turns northward. The NHC track forecast is pretty much on top of the prior one, continuing to favor the consensus aids, and is roughly in between the leftward GFS and rightward ECMWF model solutions. Users should be reminded to not focus on the exact forecast track, especially given Lee`s forecast size at the longer range, and the average day 4 and 5 track errors are about 145 and 200 miles, respectively. Data from an earlier NOAA G-IV mission sampling the environment around Lee indicated that the vertical wind shear that had been affecting the hurricane has mostly subsided, with the dropsonde data showing well-established outflow to the north, and a deep-layer of cyclonic flow to the south associated with Lee`s broad and deep circulation. While it is difficult to predict the inner-core changes associated with the cyclone, most of the intensity guidance still suggests Lee will intensify further over the next day or so, with a 120-kt peak predicted in 24 hours. Afterwards, as Lee continues to slow down, it may then begin to encounter its own cold wake due to its expanding wind field, and the hurricane is expected to begin gradually weakening. This weakening should be hastened by increasing southwesterly vertical wind shear after 72 h as the storm also traverses already cooled sea-surface temperatures by Franklin and Idalia last week. However, the model guidance also shows Lee`s 34-kt and 50-kt wind field continuing to expand through the forecast period even as the hurricane gradually weakens. KEY MESSAGES: 1. Dangerous surf and life-threatening rip currents will affect portions of the northern Leeward Islands, the Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas, and Bermuda through much of this week. 2. Lee could bring wind, rainfall, and high surf impacts to Bermuda later this week. Although it is too soon to determine the specific timing and level of those impacts, interests on Bermuda should monitor the latest forecasts for Lee. 3. It remains too soon to know what level of impacts, if any, Lee might have along the U.S. East Coast and Atlantic Canada late this 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 this 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 11/0300Z 22.6N 62.2W 105 KT 120 MPH 12H 11/1200Z 23.1N 63.1W 115 KT 130 MPH 24H 12/0000Z 23.6N 64.4W 120 KT 140 MPH 36H 12/1200Z 24.1N 65.5W 115 KT 130 MPH 48H 13/0000Z 24.6N 66.4W 110 KT 125 MPH 60H 13/1200Z 25.3N 67.2W 100 KT 115 MPH 72H 14/0000Z 26.5N 67.7W 95 KT 110 MPH 96H 15/0000Z 30.2N 67.9W 85 KT 100 MPH 120H 16/0000Z 35.5N 67.0W 70 KT 80 MPH $$ Forecaster Papin |
