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| #1106374 (Received by flhurricane at: 5:12 PM 08.Sep.2022) TCDAT1 Hurricane Earl Discussion Number 24 NWS National Hurricane Center Miami FL AL062022 500 PM AST Thu Sep 08 2022 Earl`s intensification trend from last night took an unexpected halt this morning, which was unusual given the reduction in vertical wind shear. While an SSMIS pass at 1056 UTC showed a closed mid-level eyewall, a more recent AMSR2 pass at 1717 UTC indicated that Earl likely entrained some dry air that degraded the mid-level eyewall structure, with a large cyclonic spiral opening to the west that matched conventional satellite imagery at the time. The Air Force Reserve Reconnaissance Aircraft has been sampling the hurricane this afternoon, finding a minimum central pressure of 961 mb, but similar to this morning, only found 700 mb flight level winds of 93 kt (which reduces to 83 kt) and peak SFMR winds even lower at 64 kt. Given these lastest in-situ observations, the initial intensity is adjusted to 85 kt for this advisory. The aircraft observations, in combination with ASCAT data, also indicate that Earl wind field is growing larger, with 34-kt and 50-kt radii expanding in the southeastern quadrant. Earl is beginning to accelerate to the north-northeast, with aircraft fixes indicating an estimated motion of 030/13 kt. Further acceleration and a more northeastward turn is anticipated tonight and tomorrow as Earl is caught up in the southwesterly flow between a mid-level ridge to the east, and a digging mid-latitude trough to the northwest. The guidance this cycle is very tightly clustered upon the previous forecast track in over the next 24 hours, and very few changes were made during this period for the latest NHC track. On this path, Earl should make its closest approach about 75-100 n mi southeast of Bermuda at around 0600 UTC. The same trough mentioned above is then expected to capture Earl in 48-60 hours, resulting in substantial slowdown in Earl`s motion as the two features phase together. This is the time period where the guidance continues to exhibit a lot of along-track spread, related to the degree of trough interaction, though the guidance this cycle has shifted towards a stronger phasing solution, likely resulting in a additional slowdown. The latest track forecast is not quite as slow or far east as the latest GFS or ECMWF solutions, so further adjustments may be needed if these trends continue. Deep-layer (200-850 mb) vertical wind shear over Earl is now quite low, under 10 knots per the GFS- and ECMWF-based SHIPS. However, the structural degradation in Earl`s inner core today has thrown a monkey wrench in the anticipated intensification that was expected to occur today. In fact, while the pressure has still been slowly decreasing, it seems to have resulted in the wind field growing more than strengthening the maximum sustained winds. While it is likely that Earl will be able to mix out the earlier dry-air entrainment near the core, it has shortened the window of favorable conditions for intensification before the shear begins to rapidly increase again in 36 hours. Thus, the intensity forecast has been reduced a bit this cycle, now only showing a 105 kt peak in 24 hours, which is now under the HCCA and LGEM guidance and closer to the ICVN consensus aid. After 36 hours, increasing baroclinicity will lead to a rapid increase in vertical wind shear, and extratropical transition will likely be underway (likely a warm-seclusion-type event), and be complete by 48 hours. The powerful extratropical low is then forecast to weaken steadily, in agreement with the intensity consensus aids. KEY MESSAGES: 1. Although Earl`s center is forecast to pass southeast of Bermuda, tropical-storm-force winds are expected on the island tonight into tomorrow morning. Hurricane-force winds are possible on Bermuda tonight if Earl`s track shifts farther west than currently forecast. 2. Swells generated by Earl are building near Bermuda and are expected to reach the U.S. East Coast tonight. These swells are likely to cause life-threatening surf and rip current conditions through the weekend. Please consult products from your local weather office. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 30.3N 64.4W 85 KT 100 MPH 12H 09/0600Z 32.1N 62.9W 95 KT 110 MPH 24H 09/1800Z 35.2N 59.6W 105 KT 120 MPH 36H 10/0600Z 39.2N 55.0W 100 KT 115 MPH 48H 10/1800Z 42.6N 51.8W 75 KT 85 MPH...POST-TROP/EXTRATROP 60H 11/0600Z 44.0N 50.4W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 11/1800Z 45.0N 49.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 12/1800Z 45.8N 47.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 13/1800Z 46.0N 41.4W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Papin |
