000 AXPZ20 KNHC 012135 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sun Nov 1 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning: A recent scatterometer pass indicates northerly winds of 20 to 30 kt across the Tehuantepec region and downwind to near 13N96W. Building high pressure across the eastern slopes of the Sierra Madre Mountains in Mexico and the western Gulf of Mexico will provide a very tight pressure gradient over the area, and bring an increase in winds funneling into the Gulf of Tehuantepec. Winds will rapidly increase again to gale force this afternoon, and reach minimal storm force late tonight into early Mon morning. Minimal storm conditions are also expected on Mon night. Seas will peak near 25 ft late Mon and Mon night with the strongest winds. Swell generated from this event will produce a large plume of 12 ft or greater seas that will extend about 500 nm SW of the Gulf of Tehuantepec by Mon night. Marine interests transiting across or in the vicinity the Gulf of Tehuantepec should be aware of this gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters. Please refer to the latest High Seas Forecast issued by the National Hurricane Center at: https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for further details. Potential Heavy Rainfall event: Tropical cyclone Eta over the western Caribbean along with a surge of moist southwesterly flow will support heavy to torrential rainfall across portions of Central America early this week. Eta is likely to cause life- threatening flash flooding and river flooding across portions of Central America, along with landslides in areas of higher terrain. Eta is expected to produce rainfall accumulations of 15 to 25 inches(380 to 635 mm) across central and northern Nicaragua into much of Honduras, with isolated amounts of 35 inches (890 mm). Refer to statements provided by your national meteorological service for more details. ...TROPICAL WAVES... A tropical wave is along 108W from 04N-17N, moving W at around 10 kt. Scattered moderate isolated strong convection is noted from 08N to 16N between 105W and 110W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N83W to 10N90W to 09N96W to 1011 mb low pressure near 11N113W to another 1013 mb low pressure near 11N123W to beyond 11N140W. Scattered moderate isolated strong convection is observed within about 150 nm S of the monsoon trough between 100W and 105W, from 10N to 16N between 110W and 120W, and within 90 nm SW quadrant of the low centered near 11N123W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section above for details on the Gulf of Tehuantepec Storm Warning. Of note, the 20-year climatology of the Tehuantepec gap wind events indicates that most gale-force events occurred during November and December while most storm-force winds occurred in January. Based on records, the first storm-force winds event usually occurs toward mid-November each cold season. A ridge dominates the offshore forecast waters of Baja California producing gentle to moderate northerly winds with seas of 2-4 ft. Seas will build to 4 to 6 ft in NW swell N of Cabo San Lazaro by mid-week. Gentle winds will persist south of Cabo Corrientes outside of the Gulf of Tehuantepec plume, with seas of 4 to 6 ft in mostly southerly swell. Seas may increase to 6-8 ft just S of the Revillagigedo Islands by mid-week. Mainly gentle to moderate NW winds are forecast in the Gulf of California with seas of 1-2 ft, except near the entrance to the Gulf of California where seas of 3-4 ft are expected. These marine conditions will persist for the next several days. By Fri, winds may increase across the northern part of the Gulf. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... The most recent scatterometer data show moderate to locally fresh south to southwest winds south of the monsoon trough. Large seas generated by the storm gap wind event in the Tehuantepec region will propagate across the offshore waters of Guatemala and El Salvador beginning tonight. In addition, fresh to strong NW winds associated with the same gap wind event are forecast to affect the SW part of the offshore forecast waters on Mon. Farther south, a combination of fresh SW winds and building SW swell will allow seas to reach 8 to 9 ft off western Panama and near the Azuero peninsula by tonight. As tropical cyclone Eta approaches the coast of Nicaragua on Mon, expect increasing SW flow across the offshore forecast waters of Costa Rica and Panama, including the Gulf of Panama. REMAINDER OF THE AREA... High pressure dominates the waters north of 15N. The pressure gradient between the high pressure and lower pressures associated with the monsoon trough will continue to support moderate to locally fresh NE trade winds from the monsoon trough to 20N and west of 115W, for the next several days. Seas are 5 to 7 ft across this region, in a mix of swell and easterly wind waves. Seas are forecast to build to 8 ft across the west-central waters by Tue, but mainly from 16N to 20N W of 135W. A cold front is forecast to reach 30N140W by Mon evening with winds remaining 20 kt or less. Long period NW swell will follow the front, with building seas of 8-10 ft. This swell event will reach the NW forecast waters this evening through Tue impacting the area north of 25N and west of 134W. A trough of low pressure located several hundred miles southwest of the coast of southern Mexico is producing disorganized showers and a few thunderstorms. Environmental conditions appear favorable for gradual development, and a tropical depression is likely to form by the middle of the week as the system moves west-northwestward over the eastern Pacific. The latest Tropical Weather Outlook states that this system has a low chance of tropical cyclone formation through 48 hours, and a high chance through 5 days. $$ GR