000 AXPZ20 KNHC 180308 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Wed Nov 18 2020 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...SPECIAL FEATURES... Tropical Depression Twenty-One-E is centered near 15.5N 114.3W at 0300 UTC, moving WNW at 10 kt. The estimated minimum central pressure is 1007 mb. Maximum sustained winds are 30 kt with gusts to 40 kt. The system has become better organized today, and it is expected to become a tropical storm within the next 12 hours, then weaken by Thu as it encounters a more unfavorable marine environment. Scattered moderate to strong convection is within 90 nm of the center. Scattered moderate isolated strong is noted elsewhere from 10N to 19N between 110W and 120W. Please read the latest High Seas Forecast issued by the National Hurricane Center at website- https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest Tropical Depression Twenty-One-E NHC Forecast/ Advisory and Public Advisory at www.hurricanes.gov for more details. Tehuantepec Gale Warning: A tight pressure gradient across the western Gulf of Mexico and southern Mexico is supporting strong gales across the Tehuantepec region. This event will be a long- lived, with gale force winds forecast to reach near storm force late tonight into early Wed, and again Wed night into early Thu. Wave heights are forecast to build to the range of 14-20 ft each night. Wave heights downstream of the Gulf of Tehuantepec may reach 22 ft late Wed night into early Thu. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from Tropical Storm Iota in Central America near 14N87W to 17N107W, then resumes southwest of Tropical Depression 21E near 14N116W to 11N122W to 10N129W to 08N134W. The ITCZ continues from 08N134W to beyond 08N140W. Scattered moderate isolated strong convection associated with TS Iota is north of 09N between 85W and 92W. Scattered moderate isolated strong is noted from 10N to 19N between 110W and 120W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A Gale Warning remains in effect for the Gulf of Tehuantepec. Please see the Special Features section above for details. A ridge extends across the offshore forecast waters west of Baja California, producing gentle to moderate northwesterly winds. Wave heights are 5-7 ft south of Punta Eugenia, and 7-9 ft north of Punta Eugenia, due to long-period NW swell. This swell will slowly decay through Wed. A cold front is expected to move across Baja California Norte and the northern Gulf of California on Fri. Strong high pressure building eastward behind the front will induce fresh to strong NW winds in the northern Gulf Sat night and Sun. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Enhanced west to southwest monsoonal flow west of Costa Rica and Nicaragua is due to Tropical Storm Iota, inland over Central America. These winds are expected to weaken through Wed night as Iota slowly dissipates over land. Elsewhere, moderate to fresh southwest winds are present south of the monsoon trough east of 100W, with mainly gentle west to northwest winds north of the trough. Wave heights are generally 5-7 ft. Large seas generated in the Tehuantepec region will propagate into the offshore waters of Guatemala and El Salvador through Wed night. REMAINDER OF THE AREA... See the Special Features section above for details on Tropical Depression Twenty-One-E. A cold front extends across the NW part of the discussion area from 30N128W to 24N140W. The front will push eastward and weaken during the next 24 hours, becoming a dissipating stationary front 30N122W to 23N140W by Wed evening. Large NW swell associated with the front will propagate SE and gradually diminish through Wed. A low pressure system is expected to stall near 31N140W Thu and Fri, then shift westward on Sat as a strong ridge builds north of 30N. Tropical Depression 21E will weaken later this week as it moves westward across the region. Associated seas greater than 8 ft will persist north of the remnant low due to a persistent gradient between the low and a strengthening ridge to the north. $$ Mundell