000 AXPZ20 KNHC 221601 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Tue Dec 22 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehunatepec Gale Warning: A ridge across the western Gulf of Mexico and the eastern slopes of the Sierra Madre Mountains in Mexico continues to support minimal gale force northerly winds in the Tehuantepec region this morning. These winds will diminish below gale-force late this morning into the early afternoon hours. Then, fresh to strong northerly winds will persist through Wed morning. A stronger gap wind event is in store for the Tehuantepec area beginning on Thu. Winds will begin to funnel into the Gulf of Tehuantepec by Thu afternoon, and rapidly increase to gale-force. 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, and there is still the possibility that winds may touch minimal storm force which will need to be monitored. 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 09N73W to 05N80W to 08N85W to 07N91W. The ITCZ axis extends from 07N91W to 06N110W to 07N120W to 09N132W, then resumes W of a surface trough extending along 134W from 08N135W to beyond 08N140W. Scattered moderate and isolated strong convection is noted from 06N to 08N between 102W and 105W...and from 07N to 13N between 130W and 137W. The latter convective activity is related to the surface trough. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 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 Thu through Fri night. 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 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 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 tightens 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. Large NW swell will move into the waters W of Baja California Sat night. 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. 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 up to 16-18 ft. REMAINDER OF THE AREA... High pressure located just 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 08N to 20N W of 120W. Seas are in the 8-9 ft range. A surface trough is noted from 07N to 12N along 133W/134W. The trough will move westward over the next 48 hours with an area of fresh to strong winds developing in the vicinity of it. A weak low pressure may develop along the monsoon trough near 07N103W by late today with fresh to strong winds within about 90-120 nm in the N or NE semicircle of the low center, and seas in the 8 to 11 ft range. The low will move westward, reaching near 08N115W by early Thu. 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. Winds immediately N of the front will increase to fresh to strong Sat as the pressure gradient tightens. $$ GR