000 AXNT20 KNHC 181806 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Wed Nov 18 2020 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 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1715 UTC. ...SPECIAL FEATURES... The remnant low of Iota is centered near 13.8N 89.5W at 18/1500 UTC or 17 nm WNW of San Salvador, El Salvador moving W at 10 kt. Estimated minimum central pressure is 1006 mb. Maximum sustained wind speed is 25 kt with gusts to 35 kt. The remnants of Iota are expected to produce additional rainfall accumulations through Thursday. This rainfall will lead to significant, life-threatening flash flooding and river flooding, along with mudslides in areas of higher terrain. Please read the last NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPAT1.shtml and Forecast/Advisory at https://www.nhc.noaa.gov/text/MIATCMAT1. shtml for more details. Gulf of Mexico Gale Warning: Strong autumn high pressure will continue to build southward across the Gulf of Mexico behind a stationary front that extends from the Straits of Florida to the N-central Yucatan Peninsula. The high pressure will continue to create a very tight gradient between it and the front leading to strong northeast winds, with frequent gusts to gale force over the southeastern half of the Gulf waters, including the Straits of Florida and the waters adjacent to the Yucatan Channel through early Thursday, 19/1200 UTC. Expect building seas of 10-16 ft across this area. Very hazardous conditions can be expected between the wind waves against the flow of the Gulf stream through the Straits of Florida, and due to a SE swell generated by Iota which is propagating through the Yucatan Channel. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/ MIAHSFAT2.shtml for more details. Caribbean Gale Warning: The same conditions that are occurring in the southeastern half of the Gulf of Mexico behind a stationary front approaching the basin will spread into the far northwestern Caribbean with gusts to gale force behind the front and N of 20N from this morning through early Thursday. The front is forecast to stall from eastern Cuba to the Gulf of Honduras early Thu. Large and hazardous seas will build to 8 to 13 ft through the Gulf of Honduras and the Yucatan Channel as fresh northerly wind waves behind the front mix with E-SE swell generated by Iota. The highest seas are expected in the Yucatan Channel. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details. Atlantic Gale Warning: The pressure gradient which will lead to frequent gusts to gale force over the southeastern Gulf of Mexico and far northwestern Caribbean Sea will also bring frequent gusts to the western Atlantic off the coast of South Florida and the Bahamas behind the cold front which currently extends from 31N61W to near 23N80W across the basin. These gusts will begin this evening, 19/0000 UTC through Thursday evening, 20/0000 UTC offshore the Bahamas from 22N to 27N and W of 61W. Expect seas to build to 8-14 ft with the highest first in the gulf stream, then to NE of the Bahamas by Thursday night. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details. ...TROPICAL WAVES... The axis of a low amplitude tropical wave is along 41W from the equator to 14N, moving westward at 15-20 kt. Isolated moderate convection is from 00N-10N between 34W-51W. The axis of a tropical wave is along 62W from 18N southward across the Lesser Antilles to near eastern Venezuela, moving westward around 10 kt. Isolated moderate convection is from 06N-20N between 60W-65W, and from 20N-24N between 58W-64W. The axis of a tropical wave is along 73W from Haiti southward to N Colombia, moving westward at around 10 kt. Isolated moderate convection is E of the tropical wave axis to 68W to include the ABC Islands. ...MONSOON TROUGH/ITCZ The monsoon trough axis extends from the coast of Sierra Leone near 08N12W to 07N15W. The ITCZ axis continues from 07N15W to 04N40W then resumes W of a tropical wave near 04N43W to the coast of Brazil near 02N50W. Scattered moderate convection is along the coast of Sierra Leone from 05N-09N between 11W-15W. Scattered moderate convection is from 03N-07N between 21W-34W. GULF OF MEXICO... See Special Feature section above for details on a Gale Warning in effect over the southeastern half of the Gulf of Mexico. The stationary front extends westward from the Straits of Florida near 23N80W to the north Yucatan Peninsula to the Bay pf Campeche near 19N94W. Scattered showers are within 60 nm of the front. Strong winds, frequent gusts to gale force, and building seas can be expected through tonight across the central Gulf and Straits of Florida as high pressure builds north of the area behind a front exiting the southern Gulf. In addition, southerly swell from Iota, now well inland over Central America, is moving through the Yucatan Channel. Conditions should improve by the end of the week into the weekend. CARIBBEAN SEA... Please see the Special Features section for information on Tropical Depression Iota and on a Gale Warning in effect for the northwestern Caribbean north of 20N. A quasi-stationary front is just NW of the basin and will drift into the far NW Caribbean today. Ahead of this front, fresh to strong NE winds are already occurring across the NW Caribbean due to a tight pressure gradient between the remnant of Iota and building high pressure N of the area. Mainly moderate trades prevail elsewhere, locally fresh in the eastern Gulf. Seas are 8-13 ft in the NW Caribbean in mixed NE wind waves and remnant E-SE swell generated by Iota. Seas of 3-6 ft prevail elsewhere across the basin. A 1011 mb low pressure area is noted in the SW Caribbean Sea near 12N81W. Environmental conditions are expected to be only marginally conducive for slow development over the next several days while the system moves slowly west-southwestward or westward across the southwestern Caribbean Sea. Regardless of tropical cyclone formation, areas of heavy rain are possible during the next several days from Nicaragua southward across Central America and into Colombia. These rains could cause new flooding concerns, especially across previously inundated areas. Please read the latest Tropical Weather Outlook issued by the National Hurricane Center at website www.nhc.noaa.gov/text/MIATWOAT.shtml for more details. ATLANTIC OCEAN... See the Special Features section for details on a Gale Warning in effect over the SW N Atlantic. SE of the cold front discussed above, a trough is analyzed from 31N59W to 26N65W. Scattered moderate convection is noted within 45 nm either side of the trough. Mainly moderate NE-E winds prevail W of 65W along with seas of 4-6 ft. Another dissipating cold front is over the eastern Atlantic near the Canary Islands, extending from 31N15W to 26N28W. Scattered showers are noted near the front. Associated seas of 7-10 ft have propagated S of the front reaching to 20N. Moderate to fresh easterly winds are noted across the waters E of 60W, with gentle to moderate winds between 60W-65W. Seas are 5-8 ft across the remainder of the basin in mixed swell. The cold front in the SW N Atlantic will stall from near 26N65W to near the Turks and Caicos Thu night, gradually weakening and then drifting back NW as a remnant warm front through the end of the week before dissipating by early Sat. A non-tropical area of low pressure could form between the Bahamas and Bermuda by early next week along the remnants of the front. The system could gradually develop subtropical characteristics through the middle of next week while it moves northeastward. Please read the latest Tropical Weather Outlook issued by the National Hurricane Center at website www.nhc.noaa.gov/text/MIATWOAT.shtml for more details. $$ Formosa