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| #1152740 (Received by flhurricane at: 11:03 PM 13.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 35 NWS National Hurricane Center Miami FL AL132023 1100 PM AST Wed Sep 13 2023 Both NOAA and Air Force Reserve Unit Hurricane Hunter aircraft have been investigating Lee this evening. They found that the central pressure has not changed much since earlier today, and that the hurricane still had concentric eyewalls, but these were partially open over portions of the western quadrant. The Air Force plane measured 700 mb flight-level winds as high as 105 kt and the NOAA plane found winds as high as 107 kt at a flight level of 8000 ft. Tail Doppler radar velocities from the NOAA plane were near 100 kt at elevations of 0.5 km. These observations support maintaining the intensity at 90 kt for this advisory. Satellite imagery also suggests that the eyewall is not fully closed but there is fairly intense inner-core convection. There has been a (likely temporary) decrease in forward speed and the initial motion is just west of due north or 350/8 kt. The steering scenario for the hurricane is essentially unchanged from the previous few advisories. A 500-mb trough moving into the northeastern U.S. and a mid-level ridge near eastern Atlantic Canada should cause Lee to move generally northward at a faster forward speed during the next couple of days. A slight bend to the left is likely around 48 hours while the tropical cyclone interacts with the trough. This will likely bring the center of Lee close to southeastern New England late Friday before it moves near or over Maine and Atlantic Canada later in the weekend. The official track forecast is similar to the previous one and closely follows both the simple and corrected dynamical consensus guidance. Over the next couple of days, Lee will encounter significantly increasing vertical wind shear and somewhat drier mid- to low-level air. Sea surface temperatures along the projected track decrease sharply north of around 40N latitude. These conditions should cause weakening, but since the hurricane has such a large circulation, the weakening will likely be slow. The NHC intensity forecast is near or above the highest available model guidance. Notwithstanding, there is still high confidence that Lee will be a large and dangerous cyclone when it moves near or over land on Saturday. It should again be noted that the 34- and 50-kt wind speed probabilities beyond 36 hours in the text and graphical products are likely underestimating the risk of those winds occurring. This is because the forecast wind field of Lee is considerably larger than average compared to the wind field used to derive the wind speed probability product. KEY MESSAGES: 1. Tropical storm conditions, heavy rainfall, and high surf are expected to impact Bermuda beginning early Thursday, and a Tropical Storm Warning is in effect for the island. 2. Hurricane conditions and coastal flooding are possible in portions of eastern Maine, southern New Brunswick, and western Nova Scotia on Saturday, and a Hurricane Watch has been issued for that area. Heavy rainfall in these areas may produce localized urban and small stream flooding from Friday night into Saturday night. 3. There is the potential for life-threatening storm surge flooding in portions of southeastern Massachusetts, including Cape Cod and Nantucket, late Friday and Saturday, where a Storm Surge Watch has been issued. 4. Tropical storm conditions are possible over a large portion of coastal New England, including Cape Cod, Nantucket, Martha`s Vineyard, Block Island, and portions of Atlantic Canada, where a Tropical Storm Watch has been issued. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 28.0N 67.7W 90 KT 105 MPH 12H 14/1200Z 29.6N 68.1W 90 KT 105 MPH 24H 15/0000Z 31.9N 68.0W 85 KT 100 MPH 36H 15/1200Z 34.8N 67.2W 80 KT 90 MPH 48H 16/0000Z 37.7N 66.5W 75 KT 85 MPH 60H 16/1200Z 41.0N 66.7W 65 KT 75 MPH 72H 17/0000Z 44.0N 66.3W 60 KT 70 MPH 96H 18/0000Z 49.4N 60.9W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 19/0000Z 53.7N 50.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch |
