290 AXNT20 KNHC 201048 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Thu May 20 2021 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 0940 UTC. ...SPECIAL FEATURE... A non-tropical low pressure system has developed within a broad area of cloudiness and thunderstorms near 31.5N55W, or about 600 miles east-southeast of Bermuda overnight. The low is expected to develop gale-force winds later today while it moves generally northward. The low is forecast to then move westward and southwestward over warmer waters on Friday, and will likely become a short-lived subtropical cyclone near and to the northeast of Bermuda on Friday. The system is then expected to move toward the north and northeast into a more hostile environment by late Sunday into Monday. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal plains of Guinea near 11N15W to 05N27W. The ITCZ continues from 05N27W to 03N40W to 03N51W. Scattered moderate to strong convection is noted from 03.5N to 07.5N between 17W and 23W, and within 180 nm N of the ITCZ between 33W and 51W. GULF OF MEXICO... High pressure remains stationary across the middle Atlantic states of the U.S. and extends SW to the NE Gulf this morning. The pressure gradient between this ridge and low pressure across northern Mexico is producing fresh to strong E to SE winds across most of the Gulf north of 20N and E of 94W. These prevailing winds are producing rough seas across this area of 7 to 10 ft, including the Straits of Florida. An energetic upper level trough extending from Texas southeastward into the NW Gulf continues to sustain strong and very active convection across the W central Gulf, along an eastward moving squall line that extends from the central Louisiana coast near 92W to 25N92W to 19N95W. The southeast portion of this line of convection is moving southeastward while the north portion is moving slowly east. Overnight altimeter data showed seas of 10 to 17 ft along and behind the line, and were likely generated from strong gale force winds produced by these strong thunderstorms. To the west of this activity, a surface trough stretches across the Texas coastal waters. Strong to near severe thunderstorms are expected to continue across the NW and N central Gulf of Mexico through Fri and will be capable of producing gale force winds and seas in excess of 12 ft. Meanwhile, a strong ridge stretching from eastern seaboard to the NE Gulf will continue to dominate the Gulf waters the remainder of the week. The pressure gradient between the ridge and deepening low pressure across the Southern Plains and northern Mexico will result in fresh to strong SE winds and high seas across the Gulf region tonight through Sat. Seas will peak 10 to 13 ft today through Fri in the Straits of Florida and 12 ft in the N central Gulf on Fri. CARIBBEAN SEA... Fresh to strong tradewinds are noted across the south central Caribbean south of 16N, where seas are 5 to 8 ft. Fresh to strong winds also prevail across the Gulf of Honduras south of 19N. Fair and stable atmospheric conditions generally prevail across the basin under the influence of middle level troughing and very strong upper level westerly winds. Isolated showers and thunderstorms area noted across the coastal waters of Nicaragua and across the western coastal waters of Cuba north of 21N. High pressure off the U.S. East Coast will continue to build across the western Atlantic west of 70W through Fri. This will bring fresh to strong winds across the central Caribbean through Sat. Fresh to strong winds will also occur in the lee of Cuba on Fri and Sat. Expect fresh to strong easterly winds in the Gulf of Honduras mainly at night through tonight. ATLANTIC OCEAN... A cold front extends from a newly formed 1013 mb low pressure center near 31.5N55W to 25N60W where it becomes stationary and continues into the SE Bahamas. Strong SE winds were captured by an overnight scatterometer data to the southeast of the low to 29N and to 48W. Persistent high pressure centered across North Carolina extends southward to the front, and is producing fresh to strong easterly winds north of the stationary front from about 68W to Florida and through the Straits of Florida. Seas across this area have built 8 to 10 ft. Scattered moderate isolated strong convection is seen along and within 210 nm southeast of the front to the east of 60W, and also south of the stationary front to 20N. The low pressure center near 31.5N55W will move north to northeastward today and interact with deep layered low pressure across the NW Atlantic over the next few days, and has a medium chance of gradually becoming a subtropical cyclone near or east of Bermuda. See the special features section above for more information. East of the front and low, a surface ridge passes through 31N35W to 25N46W to the coastal waters north of Hispaniola. The pressure gradient south of the ridge is producing fresh tradewinds across the Tropical Atlantic south of 15N to the east of 55W, where seas are 6 to 8 ft. The frontal boundary will weaken and dissipate through Fri as it sinks southward and approaches the Windward Passage and Hispaniola. Meanwhile, the pressure gradient between high pressure off the eastern seaboard and the frontal boundary will continue to support an area of fresh to strong easterly winds N of the front and W of 68W through late Fri. Seas will peak around 10 ft E of the Bahamas today. Large NE swell will enter the NE waters early Sat and spread across the area waters through Mon. $$ Stripling