000 WTNT42 KNHC 162049 TCDAT2 Tropical Storm Fiona Discussion Number 10 NWS National Hurricane Center Miami FL AL072022 500 PM AST Fri Sep 16 2022 The bulk of the Fiona's convective activity remains sheared to the east of the center. However, there are some initial signs of new convection developing in a small ring around the center, the low-level cloud field is thickening up a bit, and visible satellite images show high-level convective cirrus blowing from east to west. It remains to be seen if this is suggestive of some lessening of the deep-layer shear over the system and a moistening of the ambient atmosphere. The initial intensity remains 45 kt given little change in Fiona's organization since earlier today. The next Air Force Reserve reconnaissance mission is scheduled for this evening. Fiona's center jumped a bit to the north today, and it's just about to move over or just to the north of Guadeloupe. The initial motion is estimated to be 280 degrees at 13 kt, with the storm being steered westward by subtropical ridging to the north. The track forecast philosophy has not changed from earlier today. Fiona is expected to reach the western edge of the ridge, slow down, and turn northwestward by day 3, and then north-northwestward by day 5. The guidance remains in generally good agreement on this scenario, with the notable exception being the ECMWF model, which shows a smaller Fiona not turning as sharply or moving as fast as in the other models by the end of the forecast period. The new NHC track prediction is adjusted northward during the first 48-60 hours of the forecast to account for the northward jump of the center, but it otherwise falls back in line with this morning's forecast on days 3 through 5 and lies a bit to the west of the consensus aids. Assuming that recent satellite trends are a harbinger of possible strengthening, the NHC intensity forecast continues to show gradual intensification while Fiona moves across the far northeastern Caribbean Sea during the next 48 hours. Although Hispaniola's terrain could cause some weakening in the 60-72 hour period, the amount of weakening will probably depend on how much of the wind field moves over the island or remains over the adjacent waters. After 72 hours, the global models indicate that the circulation will become re-established over the far southwestern Atlantic, and the official forecast continues to show Fiona becoming a hurricane by the end of the forecast period. Key Messages: 1. Tropical storm conditions are beginning to spread across the Leeward Islands and will continue through Saturday morning. Tropical storm conditions will spread westward across the U.S. and British Virgin Islands on Saturday and Puerto Rico late Saturday and Saturday night. Tropical storm conditions are possible over Dominica tonight and within the watch area in the Dominican Republic on Sunday. 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 Haiti and the Turks and Caicos Monday through 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 strengthen gradually over the northeastern Caribbean Sea, and it could be near hurricane strength as it approaches the southern or eastern coast of the Dominican Republic Sunday afternoon. Warnings could be required for portions of the Dominican Republic tonight or on Saturday. 4. Fiona is forecast to strengthen after moving across Hispaniola early next week, and interests in the Turks and Caicos Islands and southeastern Bahamas should continue to monitor forecasts for the storm. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 16.4N 61.1W 45 KT 50 MPH 12H 17/0600Z 16.8N 62.8W 50 KT 60 MPH 24H 17/1800Z 17.2N 64.9W 50 KT 60 MPH 36H 18/0600Z 17.6N 66.6W 55 KT 65 MPH 48H 18/1800Z 18.2N 68.2W 60 KT 70 MPH 60H 19/0600Z 18.8N 69.2W 55 KT 65 MPH...OVER DOM. REPUBLIC 72H 19/1800Z 19.6N 70.2W 55 KT 65 MPH...OVER DOM. REPUBLIC 96H 20/1800Z 21.6N 71.7W 60 KT 70 MPH...OVER WATER 120H 21/1800Z 23.6N 72.2W 70 KT 80 MPH $$ Forecaster Berg