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Chill falls over the Atlantic as the official season heads towards close
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| #1017941 (Received by flhurricane at: 5:06 AM 20.Sep.2020) TCDAT5 Hurricane Teddy Discussion Number 32 NWS National Hurricane Center Miami FL AL202020 500 AM AST Sun Sep 20 2020 The convective structure of Teddy has degraded substantially since the last advisory, with no sign of an eye in conventional satellite imagery. The most recent available microwave imagery from last night suggested that Teddy still had a very well defined low to mid-level inner-core, but this has not translated to the higher levels more apparent at night. Intensity estimates have decreased, so the initial intensity has been lowered slightly to 100 kt for this advisory. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the hurricane later this morning and should provide more information about its structure and strength. Teddy`s evolution for the next few days appears to be a tale of 3 troughs. Upper-level westerly flow associated with the first upper-level trough, affecting the storm now, is the most likely reason why the hurricane`s structure has degraded and has taken on a slightly sheared appearance. Teddy will begin to encounter the 2nd trough, a deep frontal system approaching from the west, later today and that should cause the hurricane to turn north. This interaction should steer the center of Teddy east of Bermuda, but tropical storm impacts from either the large hurricane, the frontal system, or both are still likely Sunday evening through Monday night. All indications are that Teddy will then continue generally northward and merge with the frontal system, nearing Nova Scotia as an extratropical cyclone early Wednesday. Teddy`s maximum winds will likely decrease sharply after it becomes post-tropical, as shown by all the intensity guidance, but its gale and storm-force wind radii will likely increase at the same time. The cyclone should turn northeastward as the 3rd trough, another mid-latitude system, approaches from the west. Teddy could be absorbed by that feature in as soon as 120 h, though this is not explicitly shown in the forecast at this time. The spread in the track and intensity guidance is quite low and confidence in both aspects of the forecast is high. There is a little more uncertainty in the wind radii evolution, but it is clear that Teddy will produce strong winds over a wide area of the northwest Atlantic during the next couple of days. The extent of 12-foot or higher seas associated with Teddy continues to increase. See the Key Message below regarding swells caused by the hurricane. Key Messages: 1. The center of Teddy is forecast to move east of Bermuda late Sunday or Monday. Tropical storm conditions are likely on the island beginning this evening and could continue into Monday evening. 2. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada early next week, where there is an increasing risk of direct impacts from wind, rain, and storm surge. Residents there should closely monitor the progress of Teddy and updates to the forecast. 3. Large swells produced by Teddy are expected to affect portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, the east coast of the United States, and Atlantic Canada during the next few days. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 20/0900Z 28.0N 62.0W 100 KT 115 MPH 12H 20/1800Z 28.9N 62.7W 95 KT 110 MPH 24H 21/0600Z 30.4N 62.9W 90 KT 105 MPH 36H 21/1800Z 33.3N 62.1W 85 KT 100 MPH 48H 22/0600Z 37.5N 62.2W 85 KT 100 MPH 60H 22/1800Z 40.9N 63.2W 75 KT 85 MPH...POST-TROP/EXTRATROP 72H 23/0600Z 43.8N 62.3W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 24/0600Z 51.0N 54.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 25/0600Z 58.5N 41.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Zelinsky |
