000 AXPZ20 KNHC 020918 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Mon Nov 2 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning: An observation site at Salina Cruz on the southern end of the Tehuantepec isthmus recently reported gusts to 40 kt. This is a good indication that gap winds reaching at least strong gale force are active across the Gulf of Tehuantepec. The gales are due to a tight pressure gradient created by high pressure building north of the area over the western Gulf of Mexico and across the eastern slopes of the Sierra Madre Oriental mountains. Winds will likely pulse to minimal storm force this morning, and again tonight, seas building to near 25 ft. Swell generated from this event will produce a large plume of 12 ft or greater seas that will extend about 500 nm southwest of the Gulf of Tehuantepec by tonight. 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 Storm Eta over the western Caribbean along with a surge of moist southwesterly flow will support heavy to torrential rainfall across portions of Central America through mid 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. Farther west, showers and thunderstorms along a tropical wave passing 111W/112W are showing some early signs of organization. Low pressure is expected to form along this tropical wave today, and environmental conditions are favorable for further development. There is a medium chance the low will pressure will develop into a tropical depression over the next 48 hours as it moves west- northwestward to the southwest of Clarion Island through mid week, and a high chance of development through late in the week. ...TROPICAL WAVES... A tropical wave is along 111W/112W from 02N-18N, moving west at around 10 kt. Scattered moderate to isolated strong convection is noted from 10N to 15N between 105W and 120W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N83W to 10N90W to 09N95W to 12N115W to 1011 mb low pressure near 11N123W to beyond 11N140W. Scattered moderate convection is observed from 07N to 12N, east of 88W. 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 northwest of Baja California is supporting gentle to moderate northerly winds with seas of 2 to 4 ft. Seas will build to 4 to 6 ft in NW swell off Baja California 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 south of the Revillagigedo Islands by mid-week as the low pressure described in the Special Features section above develops. Mainly gentle to moderate NW winds are forecast in the Gulf of California with seas of 1 to 2 ft, except near the entrance to the Gulf of California where seas of 2 to 4 ft are expected. These marine conditions will persist for the next several days. Looking ahead, a cold front may bring strong NW winds to the waters off Baja California Norte and the Gulf of California Fri night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... 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 overnight. Farther south, a combination of fresh SW winds and building SW swell support seas to 8 to 9 ft off western Panama and near the Azuero peninsula. As Hurricane Eta approaches the Caribbean coast of Nicaragua today and tonight, 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 15N to 20N west of 135W. A cold front is forecast to reach 30N140W by this 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 waters north of 25N and west of 135W through Tue. $$ Christensen