000 AXPZ20 KNHC 230254 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Wed Dec 23 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 0230 UTC. ...SPECIAL FEATURES... Gulf of Tehunatepec Gale Warning: High pressure ridging N of the area over the Gulf of Mexico is maintaining fresh to strong northerly flow across the Tehuantepec region with seas to 8 ft. The ridging will weaken on Wed allowing for winds to diminish to 20 kt or less. A strong cold front and Arctic area of high pressure will swiftly move by N of the area later this week. Northerly winds in the Tehuantepec region will return Thu afternoon rapidly reaching gale force, and then reaching strong gale force Thu evening. Winds are then forecast to possibly reach storm force late Thu evening into early Fri. Gale conditions are then forecast to persist for the rest of Fri into early Sat before diminishing. Very large seas of 20-21 ft are possible by early Fri while a large plume of seas of 8 ft or greater will extend well SW-W of the Tehuantepec region from this event. Marine interests transiting across or in the vicinity of the Gulf of Tehuantepec should be aware of this upcoming gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website: https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northern Colombia near 10N74W to 06N80W to 07N92W. The ITCZ axis extends from 07N92W to low pressure near 07N106W to 07N120W to 10N134W. Scattered moderate and isolated strong convection is noted from 05N to 08N between 104W and 133W, and from 06N to 12N between 125W and 135W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features for details about an upcoming Gulf of Tehuantepec Gale-force event commencing Thu afternoon, then forecast to possibly reach storm force late Thu evening. Gulf of California: Light and variable flow tonight will become NW-N gentle to moderate Wed morning. The NW-N winds will increase to moderate to fresh by Wed afternoon, and then fresh to strong Wed night through Thu night as a high pressure area settles over the Great Basin area of United States. These winds are forecast to spread southward beyond the entrance of the Gulf and through Baja California Sur passages by Thu evening, when seas are forecast to briefly reach 8 ft mainly over the southern waters. Winds will diminish by the end of the week into the weekend. Mainly gentle to moderate NW-N winds will prevail across the offshore waters of Baja California through Fri. Winds will increase to moderate to fresh mainly N of Cabo San Lazaro toward the upcoming weekend as the pressure gradient tightens some there between a ridge to the W and a meandering trough over the Gulf of California. Seas to 8 ft generated by strong NW winds off the coast of California will clip the waters of Baja California Norte on Wed. Large NW swell will move into the waters W of Baja California Sat night through Sun night with seas of 8-12 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Fresh to strong NE-E winds will pulse across the Papagayo region through the next several days as high pressure remains in place over the W Caribbean. Fresh swell generated during a strong upcoming Tehuantepec region gap wind event is expected to affect the offshore waters of Guatemala and El Salvador late Thu night through Sat, with seas building up to 14-16 ft, especially Thu night and Fri. Otherwise, gentle to moderate winds will prevail on either side of the monsoon trough, except occasionally fresh near the Gulf of Panama. REMAINDER OF THE AREA... High pressure located N of the area dominates the forecast waters N of the ITCZ. A surface trough is analyzed along the ITCZ from 07N to 13N along 137W, while a 1011 mb low pressure area is analyzed near 07N106W. The pressure gradient between the high and these lower pressures is supporting fresh to strong winds in the vicinity of both features, with moderate to fresh trades elsewhere N of the ITCZ to 20N. Seas are 7-10 ft across the trade wind belt, highest near the strongest winds. The trough will move westward over the next 48 hours eventually pushing W of 140W. The low will continue to move westward as well, gradually weakening by the end of the week. A cold front is forecast to enter the NW corner of the forecast region by Thu night. Fresh to strong SW winds are expected ahead of the front Thu night. Fresh to strong northerly winds and very rough seas will follow the front. By Fri night, the front is forecast to extend from 30N126W to 24N140W, then will gradually weaken and dissipate through the weekend. A reinforcing front may clip the northern waters by the end of the weekend. Seas are forecast to peak around 15-16 ft behind the first front along 30N by Fri night into early Sat. $$ Lewitsky