000 AXNT20 KNHC 162354 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Sat Sep 17 2022 Tropical Weather Discussion for North America, Central America Gulf of Mexico, Caribbean Sea, northern sections of South America, and Atlantic Ocean to the African coast from the Equator to 31N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1800UTC surface analysis and satellite imagery through 2300 UTC. ...SPECIAL FEATURES... The center of Tropical Storm Fiona is very near Guadeloupe at 8pm AST. Tropical storm conditions and heavy rains are occurring across parts of the Leeward Islands. The storm is centered near 16.5N 61.5W at 16/0000 UTC or 10 nm NNW of Guadeloupe moving W at 13 kt. Estimated minimum central pressure is 1002 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. Peak seas of 21 ft are near and northeast of the center. Seas 12 ft or greater extend from the center of Fiona to 240 nm in the NE quadrant, 120 nm in the SE quadrant, 75 nm in the SW quadrant, and 270 nm in the NW quadrant. Fiona remains sheared, with numerous moderate to scattered strong convection within about 120 nm E semicircle. Scattered moderate to isolated strong convection is noted elsewhere from 12N to 15N between 55W and 61W. On the forecast track, the center of Fiona is expected to move across the Leeward Islands during the next few hours, near or just south of the Virgin Islands and Puerto Rico Saturday into Sunday, and approach the southern or eastern coast of the Dominican Republic Sunday afternoon. Fiona is forecast to move across the Dominican Republic Sunday night and Monday. Gradual strengthening is forecast during the next 48 hours or so before the center of Fiona reaches the Dominican Republic on Sunday. Tropical storm conditions are beginning across portions of the Leeward Islands within the warning area and will continue through Saturday. Tropical storm conditions will spread westward to the U.S. and British Virgin Islands Saturday morning, and across Puerto Rico Saturday afternoon and Saturday night. Tropical storm conditions are possible on Dominica this evening or tonight and across the watch area in the Dominican Republic beginning Sunday afternoon. 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. These rains may produce flash and urban flooding, along with mudslides in areas of higher terrain, particularly southern and eastern Puerto Rico and the eastern Dominican Republic. Swells generated by Fiona are affecting the Leeward and northern Windward Islands, and are beginning to reach the Virgin Islands and Puerto Rico. Swells will then reach the northern coast of Hispaniola, the Turks and Caicos Islands, and the southeastern Bahamas over the weekend. These conditions could cause life- threatening surf and rip current conditions. Please consult products from your local weather office. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest T.S. Fiona NHC Forecast/Advisory and NHC Public Advisory at www.hurricanes.gov for more details. ...TROPICAL WAVES... An eastern Atlantic tropical wave has its axis along 28W from 05N to 15N moving westward at 15-20 kt. Scattered moderate convection is seen on either side of the wave axis, and mainly from 07N to 12N between 23W and 32W. A central Atlantic tropical wave has its axis along 42W from 08N to 21N moving westward at 15 kt. An area of disorganized showers and thunderstorms are near the northern end of the tropical wave. Some slow development of this system is possible early next week while it moves northwestward to northward over the central subtropical Atlantic. The latest Tropical Weather Outlook gives this system a low chance of tropical cyclone formation through five days. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from the northern border of The Gambia near 13.5N16W southwestward to 11N20W to 08N28W. Scattered moderate to isolated strong convection is observed from 04N to 08N between 13W and 21W. GULF OF MEXICO... A surface trough is analyzed across the Gulf waters, and extends from 27N85W to 22N91W. Convection continues to flare up over most of Florida and the eastern Gulf. Upper diffluence is helping to induce this convective activity. Another area of showers, with embedded thunderstorms is over the SW Gulf. Gentle to moderate winds prevail across the Gulf region with seas generally in the 1-3 ft range. Winds and seas may be locally higher in and near thunderstorms. For the forecast, high pressure over the southeastern U.S. is maintaining gentle to moderate easterly breezes and slight seas, and this will continue through early next week. A surface trough over the eastern Gulf will support scattered showers and thunderstorms over the southeastern Gulf into Sat. CARIBBEAN SEA... Please see the SPECIAL FEATURES section for information on Tropical Storm Fiona, which is forecast to impact the NE Caribbean. Outside of Fiona, a band of showers and thunderstorms extends from just S of Dominican Republic all the way to NE Nicaragua. A belt of fresh to locally strong NE winds coincides with this convective activity. Scattered showers and thunderstorms are also noted over the SW Caribbean likely associated with the eastern extent of the Eastern Pacific monsoon trough. Satellite derived wind data also show gentle to moderate trades across the remainder of the basin, with the exception of an area of moderate to fresh winds over the Gulf of Honduras. Seas are generally 3-5 ft, except 5-6 ft along the belt of fresh to locally strong NE winds. For the forecast, Tropical Storm Fiona will move to 16.8N 62.8W Sat morning, 17.2N 64.9W Sat afternoon, 17.6N 66.6W Sun morning, 18.2N 68.2W Sun afternoon, 18.8N 69.2W Mon morning, and 19.6N 70.2W Mon afternoon. Fiona will change little in intensity as it moves to near 21.6N 71.7W Tue afternoon. ATLANTIC OCEAN... Please see the SPECIAL FEATURES section for information on Tropical Storm Fiona. A cold front enters the forecast area near 31N71W, and continues SW to near 29N77W. A surface trough runs from 29N78W to near SE Florida. Numerous showers and thunderstorms are over Florida and the NW Bahamas. Gentle to moderate winds are on either side of the front with seas of 3-5 ft. A frontal low over the western Atlantic Ocean a few hundred miles west-northwest of Bermuda continues to produce disorganized showers and thunderstorms. This low is expected to move eastward to east-southeastward at about 10 kt, and development into a tropical cyclone is not anticipated due to strong upper-level winds. The remainder of the Atlantic forecast waters is under the influence of a ridge, with a 1021 mb high pressure located near 29N29W. Another high pressure center of 1020 mb is near 31N53W. A frontal trough extends from 32N30W to 28N45W. Only a few showers are noted near the trough axis. Under the influence of the ridge, mainly light and variable winds are noted roughly N of 25N. Winds increase between Fiona and the ridge to the N, with fresh to strong winds reaching 20N-21N between 55W-63W based on scatterometer data. An area of fresh to strong winds NE winds, with seas of 6-8 ft, is seen from 18N-22N between 18W-23W due to the pressure gradient between the high pressure near 29N29W and lower pressures over W Africa. For the forecast west of 55W, Tropical Storm Fiona will move to 16.8N 62.8W Sat morning, 17.2N 64.9W Sat afternoon, 17.6N 66.6W Sun morning, 18.2N 68.2W Sun afternoon, 18.8N 69.2W Mon morning, and 19.6N 70.2W Mon afternoon. Fiona will change little in intensity as it moves to near 21.6N 71.7W Tue afternoon. The cold front will shift slowly eastward through the weekend. Moderate northeast winds north of the frontal boundary will continue through the most of the weekend. Scattered showers and thunderstorms are expected near the frontal boundary. $$ GR