000 AXNT20 KNHC 180907 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Tropical Depression Iota is centered near 13.7N 88.3W at 18/0900 UTC or 20 nm NW of El Papalon, El Salvador moving WSW at 11 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Additional weakening is forecast, and Iota is expected to degenerate into a post-tropical remnant low pressure system later today. Most of the deep convection associated with Iota has dissipated, however a few disjointed bands of scattered moderate and isolated strong convection are noted across portions of the western Caribbean. Life-threatening flash flooding and river flooding is expected through Thursday across portions of Central America due to heavy rainfall from Iota. Flooding and mudslides across portions of Honduras, Nicaragua and Guatemala could be exacerbated by saturated soils in place, resulting in significant to potentially catastrophic impacts. Please read the latest 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 cold 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 cold front approaching the basin will spread into the far northwestern Caribbean with gusts to gale force behind the front and N of 20N from later this morning, 18/1200 UTC through early Thursday, 19/1200 UTC. The cold 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 31N64W 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 65W. 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 near 39W/40W from the equator to 12N, moving westward at 15-20 kt. Scattered moderate convection is noted from 07N-10N between 37W-43W. The axis of a tropical wave is near 60W/61W from 21N southward across the Lesser Antilles to near the border of Guyana and Venezuela, moving westward around 10 kt. Scattered moderate convection is noted from 12N-14N between 60W-65W, and from 20N-24N between 60W-63W. The axis of a tropical wave is near 72W/73W from the western Dominican Republic southward to NE Colombia just W of the Gulf of Venezuela, moving westward at around 10 kt. Scattered moderate and isolated strong convection is noted E of the tropical wave axis to 68W with very heavy rainfall occurring along the coast of Venezuela and the ABC Islands. ...MONSOON TROUGH/ITCZ The monsoon trough axis extends from the coast of Africa near the Guinea/Sierra Leone border to 07N17W. The ITCZ axis continues from 0717W to 05N30W to 05N40W then resumes W of a tropical wave near 04N41W to the coast of Brazil near to 06N35W. The ITCZ continues west of a tropical wave near 06N38W to the coast of Brazil near 03N51W. Scattered moderate and isolated strong convection is noted from 04N-07N betwen 10W-13W. Scattered moderate convection is noted from 02N-07N between 22W-30W. Scattered moderate and isolated strong convection is noted from 05N-09N between 30W-37W, and from 02N-07N between 44W-52W with a surface trough noted from 09N45W to 05N48W. 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 cold front extends westward from the Straits of Florida near 23N80W to the N-central Yucatan Peninsula. Showers are noted along the front. A trough extends in the western Bay of Campeche from 22N95W to 18N94W. The cold front will move SE of the basin later this morning. Conditions across the basin will improve by the end of the week into the weekend as the high pressure behind the front weakens and slides eastward to the Carolinas. Expect fresh to locally strong NE-E flow E of 87W, and moderate to fresh E-SE flow W of 87W by early Sat with subsiding seas, then moderate E-SE winds E of 87W and gentle to moderate NE-E winds W of 87W by Sun evening. 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 cold front is just NW of the basin and will move into the far NW Caribbean later this morning, as is described above. Ahead of this front, fresh to strong NE winds are already occurring across the NW Caribbean due to a tight pressure gradient between Tropical Depression 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. The cold front will stall by early Thursday and will gradually wash out Friday through Saturday, and the pressure gradient N of the remnant boundary will weaken. Thus trades will weaken across the basin this weekend with marine conditions improving. A 1008 mb low pressure area is noted in the SW Caribbean Sea near 11N83W. 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 https://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 28N63W to 22N66W. Scattered moderate convection is noted within 45 nm either side of the trough N of 25N. Mainly moderate NE-E winds prevail W of 65W along with seas of 4-6 ft. Another cold front is analyzed in the eastern and central Atlantic, extending from 32N20W to 27N40W. Scattered showers are noted near the front. Associated seas of 7-10 ft have propagated S of the front reaching to 20N. A surface trough is analyzed in the tropical central Atlantic from 20N48W to 24N49W with isolated showers near the trough. 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 https://www.nhc.noaa.gov/text/MIATWOAT.shtml for more details. $$ Lewitsky