000 AXPZ20 KNHC 212123 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Mon Dec 21 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 Tehunatepec Gale Warning: A ridge along the eastern slopes of the Sierra Madre Mountains in Mexico behind a cold front currently moving across the SE Gulf of Mexico and the Yucatan Peninsula is supporting minimal gale-force winds over the Tehuantepec region which will continue through Tue morning. Seas are in 8-12 ft range with this event. A stronger gap wind event is in store for the Tehuantepec area on Thu. Winds will begin to funnel into the Gulf of Tehuantepec by Thu afternoon, and rapidly increase to gale-force by Thu evening. Then, winds will further increase to strong gale-force by Thu night. Marine guidance suggests northerly winds of 40-45 kt Thu night and Fri. Seas will peak near 20 or 21 ft during the period of the strongest winds. Gale conditions are expected to persist into early Sat morning. Swell generated from this event will produce a large plume of 8 ft or greater seas that will affect the waters beyond 100W on Fri. Marine interests should be aware of this upcoming gap wind event to avoid hazardous marine conditions. 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 05N80W to 08N85W to 06N93W. The ITCZ axis continues from 06N93W to 08N120W to 07N140W. A trough is within the ITCZ along 130W. A cluster of moderate to strong convection is noted E of the trough axis covering from 07N to 10N between 120W and 125W. Scattered moderate isolated strong convection is observed elsewhere from 07N to 10N between 125W and 130W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please, see Special Features for details about the ongoing Gulf of Tehuantepec Gale-force event. A stronger gap wind event is expected in the Tehuantepec area on Thu. Gulf of California: Gentle to moderate NW-N winds will prevail across the Gulf of California through Wed. Then, expect increasing winds of 20-25 kt Wed night trough Thu night as another high pressure area settles over the Great Basin area of U.S. These winds are forecast to spread southward beyond the entrance of the Gulf by Thu evening, when seas are forecast to briefly reach 8 ft. 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 tighten some there between a ridge to the W and a meandering trough over the Gulf of California. Seas of 8 ft, generated by strong NW winds off the coast of California, will clip the waters of Baja California Norte on Wed. 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. Gentle to moderate winds will prevail on either side of the monsoon trough. No significant swell events are forecast to reach the forecast area over the next several days. Looking ahead, swell generated in the Tehuantepec region is expected to affect the offshore waters of Guatemala and El Salvador Thu night through Fri night, with seas building of up to 14-16 ft. REMAINDER OF THE AREA... High pressure located N of the area dominates the forecast waters N of the ITCZ. The pressure gradient between the high pressure and lower pressures in the vicinity of the ITCZ is supporting moderate to fresh NE to E trades mainly from 10N to 20N W of 120W. Seas are in the 8-10 ft range. An area of fresh to strong NE-E winds is noted per scatterometer data near a surface trough located along 130W. The trough will move westward over the next 48 hours with an area of fresh to strong winds behind it. A weak low pressure may develop along the monsoon trough near 07N103W by Tue morning with fresh to strong winds within about 90-120 nm N or NE semicircle of the low center, and seas in the 8 to 11 ft range. The low will move westward, reaching near 07N109W by Wed morning, and near 08N115W by Thu morning. A decaying cold front may reach 30N140W by Thu night, and move across the NW corner of the forecast region on Fri. Fresh northerly winds and a new swell event, with seas peaking 12-14 ft are expected in the wake of the front. $$ GR