000 AXPZ20 KNHC 202105 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 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 1800 UTC surface analysis and satellite imagery through 2100 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 currently moving across the SW Gulf of Mexico 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 through Mon night. Looking ahead, marine guidance suggests a stronger gap wind event in the Tehuantepec area by Thu. Near storm-force winds of 40-45 kt and very rough seas of 14-16 ft are possible Thu night into 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 07N88W to 04N98W. The ITCZ axis extends from 04N98W to 07N120W to 08N130W to 07N140W. Scattered moderate convection is noted from 06N to 08N between 113W and 119W. 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 minimal storm conditions. Gulf of California: High pressure over the Great Basin region of U.S. currently continues to support fresh to strong NW-N winds across the Gulf of California, particularly N of 24N W of 110W. Seas remain just under 8 ft. These marine conditions will persist through tonight. Moderate to fresh northerly winds are expected over the north and central waters Wed night and Thu as another high pressure settles over the Great Basin area. Recent scatterometer data showed fresh northerly winds within about 60 nm E of Los Cabos and near the entrance to the Gulf of California, and also within about 30 nm offshore the coast of Jalisco and Colima. These winds will diminish to less than 20 kt by this evening. Mainly gentle to moderate NW-N winds will prevail across the offshore waters of Baja California, with moderate to fresh winds N of Cabo San Lazaro on Fri. This will be the result of the pressure gradient between a high pressure of 1021 mb over the NE waters near 26N128W and a meandering trough over the Gulf of California or Sea of Cortez. Long period NW swell impacting the waters N of Cabo San Lazaro will continue to subside to 4-6 ft by Mon 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. No significant swell events are forecast to reach the forecast area over the next several days. Looking ahead, swell generated in the Tehuantepec region are expected to affect the offshore waters of Guatemala and El Salvador Thu night through Fri night, with seas of up to 11-12 ft. REMAINDER OF THE AREA... High pressure of 1030 mb located N of the area near 34N131W dominates the forecast 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 20N W of 130W. Seas are in the 8-10 ft range based on recent altimeter data. The high pressure will weaken ahead of a cold front approaching 30N140W by Mon evening. This will allow the trades to weaken substantially through Tue. A weak trough may develop over the west-central waters by mid-week increasing trades again slightly. A decaying cold front may reach 30N140W by Thu night, and move across the NW corner of the forecast region on Fri. Moderate to fresh N winds and a new swell event are expected in the wake of the front. $$ GR