000 AXNT20 KNHC 202358 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Fri May 21 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 1800 UTC surface analysis and satellite imagery through 2300 UTC. ...SPECIAL FEATURES... A 1012 mb non-tropical low located about 550 NM ENE of Bermuda has gale force winds in its northern semicircle. The low is expected to move westward and west-southwestward tonight and Friday, and it will likely become a subtropical cyclone near and to the northeast of Bermuda on Friday. After that time, the system is expected to move toward the north and northeast into a more hostile environment by late Sunday into Monday. Please see High Seas forecasts issued by the NOAA Ocean Prediction Center at ocean.weather.gov/shtml/NFDHSFAT1.php for more details on this developing low pressure area. East Atlantic Gale Warning: Meteo France is forecasting gale force winds to develop near and over the Canary Islands early Friday morning (by 21/0600 UTC). Strong to near gale force winds surrounding this area will expand on Saturday to cover the area north of 26N and east of 24W, with the possibility of gale force winds continuing near the Canary Islands. Expect seas to build to 12-15 ft offshore Morocco this weekend, with 9-11 ft seas elsewhere north of 22N and east of 32W. See the High Seas Warning and High Seas Forecast products from Meteo France at weather.gmdss.org/II.html for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal border of Senegal and Guinea-Bissau near 12N17W to 05N21W. The ITCZ continues from 05N21W to 03N34W to 01N51W along the coast of NE Brazil. Isolated moderate convection is noted from 00N-06N west of 43W. GULF OF MEXICO... A disorganized area of cloudiness and thunderstorms over the western Gulf of Mexico is associated with a surface trough of low pressure. Conditions are expected to be marginally conducive for some development over the next day or so before the disturbance moves inland over the northwestern Gulf coast late Friday or Friday night. Regardless of tropical cyclone development, the system could produce heavy rainfall over portions of southeastern Texas and southwestern Louisiana on Friday and through the weekend. This system has a low chance of becoming a tropical cyclone before it moves inland late Friday. A sharp low to mid-level trough or mid-level low, the same system described in the paragraph above, is centered in the vicinity of 24N 93.5W and is spreading a large area of cloudiness and showers over the west-central and NW Gulf of Mexico. Just east of that, scattered moderate thunderstorms are seen stretching from south to north, from the western Yucatan Peninsula to SE Louisiana, between 87W-91W. Similar convection is seen just off the western tip of Cuba. A broad area of surface troughing is also present, oriented N-S along 92W. East of the trough, strong E to SE winds prevail across a large portion of the east-central Gulf of Mexico, from the Florida Straits up to near the Mouth of the Mississippi River, where seas are 8 to 11 ft. Mainly moderate wind speeds prevail over the western Gulf, west of the trough, with 5 to 7 ft seas. For the forecast, fresh to strong SE winds and high seas are expected across the Gulf region through Sat. Seas will peak tonight through Friday, with 10 to 12 ft seas in the N central Gulf and in the Straits of Florida. Scattered showers and thunderstorms, some strong, are likely across portions of the western Gulf of Mexico through Fri night. Expect gusty winds and locally higher seas in any strong thunderstorms. CARIBBEAN SEA... A stationary front extends from 21N66W westward and across eastern Cuba to 21N79W. Scattered moderate convection is noted over portions of Hispaniola, Jamaica, eastern Cuba and nearby waters. Similar convection is near western Cuba. Most of the open waters of the eastern and central Caribbean are clear of any significant precipitation. Strong convection is over the western half of the Yucatan Peninsula, northern and eastern portions of Guatemala and inland portions of far western Honduras. The east Pacific monsoon trough is enhancing scattered moderate and isolated strong convection over northern Colombia and NW Costa Rica. Fresh to strong E winds are in the south-central Caribbean and in the Gulf of Honduras, with moderate to fresh winds elsewhere, except for gentle in the NE and SW corners of the basin. Seas are 6-8 ft in the central Caribbean and 4-5 ft elsewhere. 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 through Sat. Expect fresh to strong easterly winds in the Gulf of Honduras through tonight. ATLANTIC OCEAN... See above Special Feature for a non-tropical low centered just north of our marine area of responsibility. An occluded front extends from the 1012 mb non-tropical low near 35N54W to a triple point near 34N50W. A cold front extends from the triple point to 26N56W to 21N66W, then continues W as a stationary front to 21N79W. Scattered moderate showers and isolated tstorms are near the front. A separate, weaker low of 1018 mb just E of Bermuda near 33N63W extends a cold front to 30N65W to 30N71W to 31N73W. Isolated showers and tstorms are along and within 120 nm SE of this front, mainly east of 65W. Strong ridging north of this front is causing fresh to strong NE to E winds from 20N-30N west of 70W. Seas are up to 9 ft east of the Bahamas and east of central Florida. Elsewhere across the tropical N Atlantic, the NE to E trades are moderate to fresh south of 20N and gentle elsewhere. Seas are 7 to 8 ft south of 20N and 4 to 7 ft elsewhere. For the forecast west of 65W, the stationary front from 21N66W to 21N79W will 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 along 21N will support an area of fresh to strong easterly winds N of the front and W of 68W through late Fri. Seas of 6 to 8 ft will prevail across the area through Saturday. Large NE swell will enter the waters north of 27N and east of 73W Fri night and spread across the waters through Sat night. For the forecast between 35W-65W, winds and seas are anticipated to have little change through Saturday, then diminish slightly on Sun and Mon. See Special Features section above, regarding the forecast east of 35W. $$ Hagen