ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM Hurricane Lee Discussion Number 9 NWS National Hurricane Center Miami FL AL132023 1100 AM AST Thu Sep 07 2023 Lee is rapidly intensifying. Early this morning, a well-defined low-to mid-level eye was observed in microwave imagery, a signal that is often a precursor rapid intensification (RI). Since then, Lee has developed an eye in visible and infrared imagery, with subjective Dvorak Data-T estimates quickly increasing to as high as 5.5 during the past hour or so. Satellite classifications supported an intensity of around 80 kt at 1200 UTC, but given the significant improvement in Lee's appearance since then, the advisory intensity is set at 90 kt. The track guidance remains in very good agreement on the forecast for Lee through the weekend and confidence in the track forecast is high. Lee should continue west-northwestward, gradually slowing its forward speed, moving along the southern periphery of a subtropical ridge over the central Atlantic. Confidence continues to increase that Lee will pass north of the northern Leeward Islands, though swells associated with Lee will affect the islands starting tomorrow. By the end of the forecast, the uncertainty is a little higher, with the hurricane models (HAFS, HWRF) generally being farther south than the global models. Very small changes were made to the NHC track forecast, which is between the HCCA and simple consensus aids. As stated above, RI is occuring, and will likely continue today. The question doesn't appear to be if RI continues, but rather how strong Lee will get, and how quickly will it get there. Many of the models are calling for remarkable rates of intensification, beyond rates normally seen with model forecasts. Both HAFS models forecast Lee to exceed 150 kt within the next 2 days, and even HCCA brings the hurricane above the category 5 threshold. The NHC intensity forecast has been shifted significantly higher, but is actually within the guidance envelope. It should be stressed that internal dynamics (eyewall replacement cycles) will become a factor with the maximum strength of Lee as it becomes a major hurricane. This is almost certain to lead to fluctuations in intensity that are beyond our ability to forecast at these lead times. Hurricane Hunter aircraft are scheduled to investigate Lee beginning this evening and overnight, which should provide extremely useful information about Lee's intensity during the coming days. KEY MESSAGES: 1. Lee is forecast to become a major hurricane later today, with its core moving north of the northern Leeward Islands, the Virgin Islands, and Puerto Rico this weekend and early next week. The potential for tropical storm conditions to occur in the islands is decreasing, but residents there should continue to monitor updates on Lee. 2. Swells generated by Lee are expected to reach portions of the Lesser Antilles on Friday, and the British and U.S. Virgin Islands, Puerto Rico, Hispaniola, the Bahamas, and Bermuda this weekend. These swells are likely to cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 16.4N 50.0W 90 KT 105 MPH 12H 08/0000Z 17.1N 51.7W 115 KT 130 MPH 24H 08/1200Z 18.2N 54.0W 130 KT 150 MPH 36H 09/0000Z 19.2N 56.1W 140 KT 160 MPH 48H 09/1200Z 20.1N 58.1W 140 KT 160 MPH 60H 10/0000Z 20.9N 59.8W 135 KT 155 MPH 72H 10/1200Z 21.5N 61.2W 135 KT 155 MPH 96H 11/1200Z 22.6N 63.7W 125 KT 145 MPH 120H 12/1200Z 23.6N 66.0W 120 KT 140 MPH $$ Forecaster D. Zelinsky NNNN