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| #1107288 (Received by flhurricane at: 5:11 AM 15.Sep.2022) TCDAT2 Tropical Storm Fiona Discussion Number 4 NWS National Hurricane Center Miami FL AL072022 500 AM AST Thu Sep 15 2022 The satellite presentation of Fiona has not changed much overnight. The low-level center of the storm is still displaced to the west of a deep convective mass with very cold infrared cloud tops. Earlier scatterometer data showed a broad area of tropical-storm-force winds over the eastern portion of the circulation, with reliable peak winds in the 40-45 kt range. Therefore, the initial intensity is held at 45 kt for this advisory. An Air Force Hurricane Hunter aircraft is scheduled to investigate Fiona later today. Fiona is moving westward at 270/11 kt. The cyclone is expected to generally maintain a westward heading for the next few days as it is steered by the subtropical ridge over the central Atlantic. However, there are still significant along-track differences among some of the model solutions, with the GFS and ECMWF almost 250 n mi apart at 72 h. The latest NHC track forecast lies slightly south of the previous one and is a bit slower through the first 72 h, remaining closer to the latest GFEX and HCCA aids. This track brings Fiona across the northern Leeward Islands by Friday night, near the Virgin Islands and Puerto Rico this weekend, and near Hispaniola early next week. From there, the deterministic guidance and most GFS and ECMWF ensemble members agree that Fiona should turn northwestward by days 4-5 as a weakness develops in the steering ridge over the western Atlantic. The stronger GFS and HWRF runs show a sharper recurvature than the rest of the guidance, but the NHC forecast shows a more gradual turn generally in line with the HCCA aid. The sheared, asymmetric structure of Fiona does not appear conducive for much strengthening in the near term. In fact, the SHIPS guidance suggests that moderate to strong westerly to northwesterly shear will persist for the next several days over Fiona. This, combined with some drier mid-level air to the west of the storm, could make it difficult for Fiona`s inner-core structure to become better organized. The intensity forecast is also complicated by the potential for land interaction as the storm moves near or over portions of the Greater Antilles this weekend and early next week. Given the less-than-ideal conditions, the official NHC intensity forecast does not show much strengthening over the next several days, and it lies slightly below the intensity consensus aids. Additional tropical storm watches or warnings will likely be required later today for portions of the northern Leeward Islands, Puerto Rico, and the Virgin Islands, and interests in these locations should monitor the latest forecast updates. Key Messages: 1. Tropical storm conditions are possible in portions of the northern Leeward Islands by Friday night, where a Tropical Storm Watch has been issued. 2. Heavy rains from Fiona will reach the northern Leeward Islands Friday afternoon, spreading to the British and U.S. Virgin Islands and Puerto Rico Saturday into Sunday morning, and reaching eastern Hispaniola Sunday. This rainfall may produce flash and urban flooding, along with isolated mudslides in areas of higher terrain. 3. Fiona is expected to move near the Virgin Islands, Puerto Rico, and Hispaniola this weekend and early next week, and Tropical Storm Watches will likely be issued for some of those areas later today. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 16.6N 53.0W 45 KT 50 MPH 12H 15/1800Z 16.7N 54.7W 45 KT 50 MPH 24H 16/0600Z 16.8N 57.3W 50 KT 60 MPH 36H 16/1800Z 17.0N 59.8W 50 KT 60 MPH 48H 17/0600Z 17.2N 62.3W 50 KT 60 MPH 60H 17/1800Z 17.4N 64.4W 50 KT 60 MPH 72H 18/0600Z 17.7N 66.1W 50 KT 60 MPH 96H 19/0600Z 18.8N 68.6W 50 KT 60 MPH 120H 20/0600Z 21.0N 70.5W 55 KT 65 MPH $$ Forecaster Reinhart |
