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| #1107430 (Received by flhurricane at: 5:03 AM 16.Sep.2022) TCDAT2 Tropical Storm Fiona Discussion Number 8 NWS National Hurricane Center Miami FL AL072022 500 AM AST Fri Sep 16 2022 Fiona remains a sheared tropical cyclone this morning. The center of the storm is fully exposed to the west of a large area of deep convection over much of the eastern portion of the circulation. An Air Force Reserve Hurricane Hunter aircraft that investigated Fiona found peak 925 mb flight-level winds of 60 kt, which would support a surface wind of about 45 kt using a standard reduction factor. Meanwhile, the SFMR data only supported surface winds of 35-40 kt. Earlier scatterometer data showed an area of winds slightly above 40 kt in the northeastern quadrant of the storm. Based on these data, the initial intensity is set at 45 kt for this advisory. The latest aircraft fixes indicate that Fiona is still moving south of due west, and its initial motion is estimated to be 260/13 kt. The models agree that Fiona should move generally westward over the next couple of days, to the south of the subtropical ridge across the central and western Atlantic. This brings the center of the storm across the Leeward Islands tonight and near the Virgin Islands and Puerto Rico on Saturday through early Sunday. Then, a turn toward the west-northwest and northwest is forecast as the storm reaches a weakness in the steering ridge. This would bring the center of Fiona near or over Hispaniola on Monday and then into the southwestern Atlantic by days 4-5. The NHC track forecast has once again been adjusted slightly south of the previous one in the near term, but generally lies near the center of the guidance envelope on days 3-5. Some short-term intensity fluctuations are possible given the sheared, asymmetric structure of the storm. However, there are some indications that the environmental conditions could become more conducive for strengthening as the storm moves into the eastern Caribbean this weekend. In particular, increasing upper-level divergence and mid-level moisture along with decreasing vertical wind shear could allow Fiona to become better organized before it reaches Hispaniola. The latest NHC intensity forecast shows a bit more strengthening through 72 h, but still lies slightly below the guidance consensus. From there, the intensity forecast is of lower confidence as the extent of land interaction is still uncertain. Key Messages: 1. Tropical storm conditions are expected in the Leeward Islands within the warning area by this evening. Tropical storm conditions are possible within the watch area across the Virgin Islands beginning on Saturday, and then reaching Puerto Rico late Saturday and Saturday night. 2. Heavy rains from Fiona will reach the Leeward Islands by this evening, spreading to the British and U.S. Virgin Islands and Puerto Rico Saturday, reaching the Dominican Republic Sunday, and the Turks and Caicos Monday night or Tuesday. This rainfall may produce considerable flood impacts including flash and urban flooding, along with mudslides in areas of higher terrain. 3. Fiona is expected to move near Hispaniola early next week, and watches could be required for parts of the island later today. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 15.7N 58.1W 45 KT 50 MPH 12H 16/1800Z 15.9N 60.0W 50 KT 60 MPH 24H 17/0600Z 16.3N 62.5W 50 KT 60 MPH 36H 17/1800Z 16.7N 64.6W 55 KT 65 MPH 48H 18/0600Z 17.0N 66.3W 55 KT 65 MPH 60H 18/1800Z 17.3N 67.8W 60 KT 70 MPH 72H 19/0600Z 18.1N 69.2W 60 KT 70 MPH 96H 20/0600Z 20.0N 71.0W 55 KT 65 MPH 120H 21/0600Z 22.0N 72.5W 60 KT 70 MPH $$ Forecaster Reinhart |
