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Chill falls over the Atlantic as the official season heads towards close
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| #1017255 (Received by flhurricane at: 4:54 PM 16.Sep.2020) TCDAT5 Hurricane Teddy Discussion Number 18 NWS National Hurricane Center Miami FL AL202020 500 PM AST Wed Sep 16 2020 Recent satellite imagery is suggesting that Teddy is undergoing some westerly vertical wind shear, as indicated by outflow being more limited in the western portion of the circulation. The latest UW-CIMSS shear analysis suggests the magnitude of this shear could be about 10-15 kt, which could help to explain the lack of increase in organization of the cyclone today. The most recent Dvorak satellite intensity estimates provided CI values of 4.5-5.0, indicating that the initial intensity is still around 85 kt. The environmental conditions are not forecast to change much for Teddy over the next couple of days. The cyclone is forecast to move over warm waters within a somewhat dry atmospheric environment, while moderate shear is expected to continue due to an upper trough to its northwest. Based on these only somewhat favorable conditions for strengthening, along with what we have witnessed with the lack of intensification today, the NHC intensity forecast over the next few days is being lowered. Beyond day 3, there is evidence to suggest that Teddy may move over some cooler waters due to upwelling caused by Paulette. And, by day 4 global models are forecasting a further increase in vertical wind shear. These two factors should cause the cyclone to weaken late in the forecast period. This updated intensity forecast is in good agreement with the HFIP corrected consensus, HCCA. Teddy is moving northwestward at about 11 kt. This motion is forecast to continue for the next few days, as the cyclone is steered by a mid-level ridge to its north and northeast. Late in the forecast period, the portion of the ridge north of Teddy is expected to erode as a mid-latitude trough digs across the northeastern United States. This evolution should cause the cyclone to turn north-northwest and possibly north by day 5. The track guidance is tightly clustered through day 3, but increases quite a bit after that time, likely due to how the models are handling the approaching trough. The latest GFS delays a turn and shows a more westerly track, with the cyclone southwest of Bermuda by day 5, while the rest of the global models turn the system north sooner and take the system just east of Bermuda. The NHC track forecast is close to the previous one and is near the various multi-model track consensus aids. On the forecast track, Teddy could make a close to approach to Bermuda in about 5 days. However, based on the model spread at that time frame and average track error of about 200 n mi at 120 h, it is certainly too soon to know what impacts Teddy may have on the island. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 17.5N 50.8W 85 KT 100 MPH 12H 17/0600Z 18.6N 52.0W 90 KT 105 MPH 24H 17/1800Z 20.0N 53.4W 100 KT 115 MPH 36H 18/0600Z 21.5N 54.9W 105 KT 120 MPH 48H 18/1800Z 23.0N 56.3W 105 KT 120 MPH 60H 19/0600Z 24.8N 58.0W 100 KT 115 MPH 72H 19/1800Z 26.5N 60.2W 100 KT 115 MPH 96H 20/1800Z 29.5N 63.6W 90 KT 105 MPH 120H 21/1800Z 33.3N 64.6W 85 KT 100 MPH $$ Forecaster Latto |
