000 AXPZ20 KNHC 200838 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sun Dec 20 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 0800 UTC. ...SPECIAL FEATURES... Gulf of Tehunatepec Gale Warning: High pressure building along the eastern slopes of the Sierra Madre Mountains in Mexico behind a cold front moving across the SW Gulf of Mexico later today will induce the next round of gale-force winds over the Tehuantepec region tonight through Tue. Seas will peak around 12-13 ft with this event tonight into Mon. Looking ahead, marine guidance suggests a very strong gap wind event in the Tehuantepec area by Thu. Storm conditions and very rough seas are possible by Thu night. 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 05N81W to 07N88W to 04N97W. The ITCZ axis extends from 04N97W to 08N120W to 09N130W to 07N140W. Scattered moderate convection is noted from 06N to 08N between 89W and 92W, from 09N to 11N between 120W and 127W, and from 07N to 10N between 130W and 135W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features for details about the Gulf of Tehuantepec Gale Warning, as well as an outlook on possible Storm Conditions. Gulf of California: High pressure over the Great Basin region of U.S. currently supports fresh to strong NW-N winds across the Gulf of California, particularly N of 24N to 29N W of 110W. Fresh to strong NW-N winds will persist across most of the Gulf through this evening. Seas will remain just under 8 ft. Similar weather conditions are expected Wed night and Thu, but mainly over the central waters, with building seas of 5-7 ft. Mainly gentle to moderate NW-N winds will prevail across the offshore waters of Baja California. Fresh to locally strong northerly winds are expected within about 60 nm offshore Los Cabos and Cabo Corrientes through this afternoon. Long period NW swell impacting the waters N of Cabo San Lazaro will slowly subside through later today. 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 elsewhere. No significant swell events are forecast through early next week. Looking ahead, fresh to strong northerly winds and building seas may affect the offshore waters of Guatemala and El Salvador by Thu night into Fri. REMAINDER OF THE AREA... High pressure dominates the waters north of the ITCZ. The pressure gradient between the high pressure and lower pressures near the ITCZ is causing fresh to locally strong NE to E trades, mainly from 09N to 22N W of 120W as indicated by recent scatterometer data. Seas are in the 8-11 ft range. The high pressure will weaken ahead of a cold front reaching 30N140W by Mon evening. This will allow the trades to weaken substantially later today through Tue. A weak trough may develop over the west- central waters by mid-week increasing trades again slightly. A decaying cold front may slip SE of 30N140W by Thu night. Additional pulses of long period NW swell will reach the NW corner of the forecast area by late Sun. Large NW swell may reach the NW corner Thu night behind the decaying cold front. $$ Lewitsky