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Hurricane Teddy Forecast Discussion Number 34
2020-09-20 22:56:35| National Hurricane Center (Atlantic)
Issued at 500 PM AST Sun Sep 20 2020 542 WTNT45 KNHC 202056 TCDAT5 Hurricane Teddy Discussion Number 34 NWS National Hurricane Center Miami FL AL202020 500 PM AST Sun Sep 20 2020 Satellite images show that Teddy is continuing to maintain a central core, albeit eroded on the western side due to shear and dry air. However, the latest microwave data show a more distinct eye than conventional data would indicate, along with an open eyewall. The initial intensity is held at 90 kt, pending Air Force Reserve Hurricane Hunter aircraft data this evening. The hurricane has turned north-northwestward and is likely to turn northward tonight and north-northeastward tomorrow due to an approaching large mid-latitude trough. By early Tuesday, the cyclone should turn back to the north-northwest as it rotates around the same trough, then turn northeastward early Wednesday ahead of yet another trough moving into from eastern Canada. Track model guidance remains in very good agreement, and only a slight westward adjustment was made to the forecast. The global models are in excellent agreement on Teddy transitioning into a large non-tropical low between Bermuda and Nova Scotia in about 2 days. In many respects, the upcoming trough interaction reminds me of an extratropical transition like Sandy 2012, thankfully happening at a good distance from land, with the GFS/ECMWF models showing pressures into the 940s tomorrow, a slight increase in maximum winds, and a large increase in the size of the tropical-storm-force winds. Beyond Tuesday, the hurricane should become post-tropical near or south of Nova Scotia and be absorbed by a larger extratropical low after day 4 to the northeast of Newfoundland. Little change was made to the official forecast, other than show a small increase tomorrow as the peak extratropical forcing deepens the cyclone. It is still worth noting every model has a rather large and strong post-tropical cyclone near Nova Scotia in 2-3 days, with hazards that will extend a very long way from the center. Extremely dangerous surf conditions with 20-ft waves have been reported on the south shore of Bermuda, and officials are encouraging residents to avoid going into or near the water. Key Messages: 1. The center of Teddy is forecast to move east of Bermuda on 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 late Tuesday through Thursday, where there is an increasing risk of direct impacts from wind, rain, and storm surge. A Tropical Storm Watch has been issued for portions of Nova Scotia, and heavy rain is also expected across sections of Atlantic Canada. 3. Large swells produced by Teddy are expected to affect portions of Bermuda, the Leeward Islands, the Greater Antilles, the Bahamas, 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 20/2100Z 29.0N 63.4W 90 KT 105 MPH 12H 21/0600Z 30.1N 63.5W 85 KT 100 MPH 24H 21/1800Z 32.8N 62.6W 90 KT 105 MPH 36H 22/0600Z 36.9N 63.0W 90 KT 105 MPH 48H 22/1800Z 40.0N 64.0W 85 KT 100 MPH 60H 23/0600Z 42.7N 63.5W 75 KT 85 MPH...POST-TROP/INLAND 72H 23/1800Z 46.0N 61.3W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 24/1800Z 54.5N 50.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 25/1800Z...DISSIPATED $$ Forecaster Blake
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