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| #1158322 (Received by flhurricane at: 4:59 PM 21.Oct.2023) TCDAT5 Hurricane Tammy Discussion Number 14 NWS National Hurricane Center Miami FL AL202023 500 PM AST Sat Oct 21 2023 Tammy passed just east of Guadeloupe around 18Z and is now located near Antigua. Radar imagery continues to show a tight and well-organized inner core, and the earlier aircraft data indicated that the hurricane-force winds were confined to that region. Despite Tammy having passed just east of Dominica and Guadeloupe today, surface observations indicate that winds did not get particularly high at those locations due to Tammy being a very compact hurricane. The initial intensity is held at 75 kt based on the earlier aircraft data and steady state appearance in radar images. Both the NOAA and Air Force Hurricane Hunters are scheduled to investigate Tammy again this evening. The hurricane is moving north-northwestward, 335 degrees, at 9 kt. A continued northwest to north-northwest motion is expected during the next 12-24 hours, taking the core of Tammy over or just east of the Leeward Islands during that time. After the hurricane pulls north of the islands on Sunday, a turn to the north seems likely when the system moves in the flow between a ridge over the central Atlantic and a large trough over the western Atlantic. The spread in the guidance continues to be very large in the 4- and 5-day time frame. In fact, the difference in the model predicted center positions of Tammy at day 5 is more than 1000 miles. The NHC intensity forecast is similar is the previous one through day 3, but is again slower than the earlier forecast at days 4 and 5, trending toward the HCCA guidance. Tammy is expected to remain over very warm 29 to 30 C SSTs during the next few days, however, it will also remain in a moderate wind shear environment. These conditions will likely result in slow strengthening during the next few days. The opportunity for strengthening will likely end early next when Tammy moves into a region of stronger shear, which should cause a weakening trend. The NHC intensity is again nudged upward, trending toward the latest consensus models. However, the intensity forecast at long range is of low confidence since Tammy`s future strength will likely be correlated to the track. KEY MESSAGES: 1. Hurricane and tropical storm conditions are expected in portions of the Leeward Islands through early Sunday. 2. The heaviest rains from Tammy will continue over the Leeward Islands through Sunday. This rainfall may produce isolated flash and urban flooding, along with isolated mudslides in areas of higher terrain. 3. A storm surge could produce coastal flooding in areas of onshore winds as the center of Tammy moves near or over the Leeward Islands. Near the coast, the surge will be accompanied by large and dangerous waves. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 17.0N 61.3W 75 KT 85 MPH 12H 22/0600Z 18.1N 62.1W 75 KT 85 MPH 24H 22/1800Z 19.5N 62.9W 80 KT 90 MPH 36H 23/0600Z 20.9N 63.5W 85 KT 100 MPH 48H 23/1800Z 22.2N 63.7W 85 KT 100 MPH 60H 24/0600Z 23.1N 63.6W 85 KT 100 MPH 72H 24/1800Z 23.8N 63.4W 85 KT 100 MPH 96H 25/1800Z 25.6N 62.9W 75 KT 85 MPH 120H 26/1800Z 28.0N 62.6W 60 KT 70 MPH $$ Forecaster Cangialosi |
