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Hurricane Teddy Forecast Discussion Number 21
2020-09-17 17:03:23| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Thu Sep 17 2020 000 WTNT45 KNHC 171502 CCA TCDAT5 Hurricane Teddy Discussion Number 21...Corrected NWS National Hurricane Center Miami FL AL202020 1100 AM AST Thu Sep 17 2020 Corrected to add Key Messages Since the previous advisory, Teddy's satellite appearance has steadily improved. There is now a ragged warming eye surrounded by a ring of convection with cloud tops colder than -60 degrees C. Very recently the objective satellite intensity estimates from UW-CIMSS have been rapidly increasing. And although a blend of the 1130 and 1200 UTC Dvorak intensity estimates from SAB and TAFB, respectively, averaged out to an intensity of about 95 kt, the improved satellite presentation since that time suggests that the hurricane should have winds of at least 105 kt, which is the initial intensity for this advisory, which could even be a little conservative based on the latest UW-CIMMS ADT and SATCON values of 120 and 111 kt, respectively. There will be NOAA and Air Force Reserve Hurricane Hunter aircraft inside Teddy later today, which should provide much more detail on the structure and intensity of Teddy. The only negative factor for intensification during the next 24 h is about 10 to 15 kt of vertical wind shear. However, Teddy has been able to begin the latest burst of intensification despite that shear. Therefore additional strengthening is anticipated through this evening, and Teddy is forecast to become a category 4 hurricane by tonight. The overall environment does not change significantly for the next couple of days, so other than some fluctuations intensity such as due to potential eyewall replacement cycles, no change in strength is indicated during that time. As Teddy continues moving northwest over the weekend, it is likely to begin to encounter some of the cooler waters upwelled by Hurricane Paulette last week. This could cause the cyclone to slowly weaken. By late this weekend, increasing vertical wind shear should also contribute to weakening. Due to the fast increase in intensity this morning, the latest NHC intensity is a bit higher than all of the guidance for the first 48 h, but the overall intensity trends are closely mirrored by the various multi-model consensus. Beyond 48 h, the NHC forecast closely follows the LGEM guidance. Teddy continues to move northwestward at 10 kt. The track forecast and reasoning both remain straightforward and unchanged for the next 72 h. The latest NHC model guidance is in excellent agreement that a deep-layer ridge situated over the central Atlantic will force Teddy on a northwestward track toward the western Atlantic. There is a little less divergence among the models on days 4 and 5 then on previous cycles, and these differences are due to timing differences in where and how fast the hurricane begins to recurve ahead of an approaching mid-latitude trough and frontal system moving off the coast of the eastern United States in about 3 days. The new NHC track forecast is little changed from the previous one, and is in the middle of the tightly clustered track guidance. On the forecast track, Teddy will make its closest approach to Bermuda on Monday. Key Messages: 1. Teddy is expected to approach Bermuda as a hurricane this weekend and make its closest approach to the island late Sunday or Monday. While the exact details of Teddy's track and intensity near the island are not yet known, the risk of strong winds, storm surge, and heavy rainfall on Bermuda is increasing. 2. Swells produced by Teddy are expected to affect portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, and the southeastern United States late this week and into the weekend. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 19.3N 53.0W 105 KT 120 MPH 12H 18/0000Z 20.4N 54.0W 115 KT 130 MPH 24H 18/1200Z 21.8N 55.5W 115 KT 130 MPH 36H 19/0000Z 23.5N 57.0W 115 KT 130 MPH 48H 19/1200Z 25.5N 58.9W 110 KT 125 MPH 60H 20/0000Z 27.3N 60.9W 105 KT 120 MPH 72H 20/1200Z 28.7N 62.7W 100 KT 115 MPH 96H 21/1200Z 32.4N 63.4W 95 KT 110 MPH 120H 22/1200Z 38.9N 62.3W 85 KT 100 MPH $$ Forecaster Latto
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