000 AXNT20 KNHC 161200 TWDAT Tropical Weather Discussion...UPDATED NWS National Hurricane Center Miami FL 1205 UTC Fri Sep 16 2022 Updated to include information from the 1200 UTC Intermediate Advisory for Tropical Storm Fiona 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 0600 UTC surface analysis and satellite imagery through 1015 UTC. ...SPECIAL FEATURES... Tropical Storm Fiona is centered near 15.8N 58.8W at 16/1200 UTC or 150 nm E of Guadeloupe moving W at 13 kt. Estimated minimum central pressure is 1004 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. Wave heights are currently peaking at 20 to 22 ft near and northeast of the center. The radii of wave heights 12 ft or greater extends outward up to from the center of Fiona to 270 nm in the NE quadrant and 240 nm in the NW quadrant. Fiona remains a sheared tropical cyclone as noted by the its fully exposed center to the west of a large area of numerous moderate to isolated strong convection noted from 13N to 17N between 51W-58W as noted in satellite imagery. Fiona is forecast to maintain a westward motion with a gradual decrease in forward speed expected through Sat night or early on Sun, followed by a turn toward the west-northwest later on Sunday. On the forecast track, the center of Fiona is expected to move across the Leeward Islands tonight and early Sat, and move near or just south of the Virgin Islands and Puerto Rico late Sat into Sun. Tropical storm conditions are expected across portions of the northern Leeward Islands within the warning area beginning this evening. Tropical storm conditions are possible within the watch area across the Virgin Islands on Saturday and in Puerto Rico late Sat or Sat night. Heavy rains from Fiona will reach the Leeward Islands this afternoon, spreading to the British and U.S. Virgin Islands and Puerto Rico Saturday into Sun morning, and reaching eastern Hispaniola Sunday. This rainfall may produce considerable flood impacts including flash and urban flooding, along with mudslides in areas of higher terrain particularly southern Puerto Rico and eastern Dominican Republic. Swells generated by Fiona are beginning to affect the Leeward Islands and will spread westward to the Virgin Islands and Puerto Rico on today through Sat. These swells 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 Public Advisory at www.hurricanes.gov for more details. ...TROPICAL WAVES... A far eastern Atlantic tropical wave has its axis along 24W from 02N to 15N moving westward at 15 kt. Scattered moderate to isolated convection is ahead of the wave from 06N to 14N between the wave and 29W. A central Atlantic tropical wave has its axis along 39W from 05N to 20N moving westward at 15 kt. Scattered showers and isolated thunderstorms are within 180 nm either side of the wave from 16N to 20N. Some slow development of this system is possible late this weekend and early next week while it moves northwestward to northward over the central subtropical Atlantic. The current outlook assigns a low probability of tropical cyclone formation through both 48 hours and 5 days. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from the coast of Mauritania near 17N16W southwestward to 12N24W to 13N30W and northwest to 15N38W. Associated convection in the area is described in the tropical wave section above. GULF OF MEXICO... A weakening stationary boundary extends from near Crystal River, Florida to 28N86W, while a surface trough is analyzed from the Florida southwest coast to just north of the northeast tip of the Yucatan Peninsula. These features are supporting scattered moderate convection within about 120 nm of the Florida coast. Similar convection is also noted along a trough in the southern Bay of Campeche. Outside of convective activity, generally gentle to moderate east winds are across the majority of the basin per latest ASCAT data passes. Wave heights remain relatively low, in the 1-3 ft range. For the forecast, the weakening stationary front will dissipate today as high pressure builds over the southeastern U.S. into the weekend. This will maintain gentle to moderate easterly breezes and slight seas through early next week. The surface trough will continue to support convection over the southeastern Gulf into Sat. CARIBBEAN SEA... Tropical Storm Fiona is forecast to impact the northeast Caribbean. Please refer to the Special Features Section for more details. The gradient between subtropical high pressure and lower pressure over the southern Caribbean is supporting moderate to fresh easterly flow across the majority of the basin. Wave heights are 4-6 ft in the eastern and central basin and 3-5 ft in the northwestern Caribbean. For the forecast, Tropical Storm Fiona near 15.8N 58.8W 1004 mb at 8 AM EDT moving W at 13 kt. Maximum sustained winds 45 kt gusts 55 kt. Fiona will maintain intensity as it moves to near 15.9N 60.0W this afternoon, to near 16.3N 62.5W late tonight, then begin to gradually strengthen as it moves to near 16.7N 64.6W Sat afternoon with maximum sustained winds 55 kt gusts 65 kt, move to near 17.0N 66.3W late Sat night, to near 17.3N 67.8W Sun afternoon with maximum sustained winds 60 kt gusts 75 kt and to near 18.1N 69.2W late Sun night. Fiona will change little in intensity as it reaches near 20.0N 71.0W late Mon night and to near 22.0N 72.5W late Tue night. Relatively weak high pressure will build behind Fiona. ATLANTIC OCEAN... Tropical Storm Fiona is the main feature impacting portions of the Atlantic. Please refer to the Special Features Section for more details. A cold front is over the western Atlantic extending from weak low pressure of 1015 mb near 32N74W southwestward to 29N80W, where it transitions to a weakening stationary front to inland central Florida and to the eastern Gulf of Mexico. Behind the front, winds are moderate northeast winds are present along with wave heights of 4-6 ft seas. Ahead of the front, winds are gentle to moderate, southeast in direction, along with wave heights of 2-4 ft. Riding associate to high pressure of 1021 near 29N60W dominates the central Atlantic. The related gradient is allowing for light to gentle winds and wave heights of 3-5 ft due to a north swell. A surface trough extends from near 31N41W to 28N47W. No convection is occurring with this feature. A tighter pressure gradient in the eastern Atlantic between high pressure of 1201 mb near 31N27W and lower pressure to its southeast and south in the vicinity of the monsoon trough is supporting moderate to fresh northeast winds and 6-8 ft wave heights. For the forecast west of 55W, Tropical Storm Fiona is near 15.7N 58.8W 1004 mb at 8 AM EDT moving W at 13 kt. Maximum sustained winds 45 kt gusts 55 kt. Fiona will maintain intensity as it moves to near 15.9N 60.0W this afternoon, to near 16.3N 62.5W late tonight, then begin to gradually strengthen as it moves to near 16.7N 64.6W Sat afternoon with maximum sustained winds 55 kt gusts 65 kt, move to near 17.0N 66.3W late Sat night, to near 17.3N 67.8W Sun afternoon with maximum sustained winds 60 kt gusts 75 kt and to near 18.1N 69.2W late Sun night. Fiona will change little in intensity as it reaches near 20.0N 71.0W late Mon night and to near 22.0N 72.5W late Tue night. A cold front extends from weak low pressure of 1015 mb near 32N74W southwestward to 29N80W, where it transitions to a weakening stationary front to inland central Florida. The cold front will shift eastward through the weekend as the stationary boundary gradually weakens. Moderate to 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. $$ Aguirre/Mahoney