000 AXPZ20 KNHC 212131 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Tue Dec 21 2021 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 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 2120 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: High pressure building behind a cold front moving across the Gulf of Mexico will support gap winds to minimal gale force over the Gulf of Tehuantepec through tonight. Seas will build to 8 to 11 ft with the strongest winds. Fresh to strong northerly winds will persist across the Gulf of Tehuantepec through early Fri morning. An earlier altimeter satellite pass indicated seas were already reaching 9 ft within 90 nm offshore in the Gulf of Tehuantepec. Seas 8 ft or greater generated by this gap wind event will reach as far west as 12N97W. Please read the latest NWS High seas Forecast issued by the National Hurricane Center at website: https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. Of note, the 20-year Climatology of the Tehuantepec gap wind events indicates that on average 16 gale-force events and 5 storm-force events occur in the Gulf of Tehuantepec per cold season. Most gale-force events occurred during November and December, while most storm-force winds occurred in January. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 1008 mb low pressure near 08N78W to 09N87W to 1011 mb low pressure near 08.5N125W to 09N132W. No significant convection is evident. OFFSHORE WATERS WITHIN 250 NM OF MEXICO A Gale Warning remains in effect for the Gulf of Tehuantepec. Please, see the Special Features section for details. 1021 mb high pressure is centered west of Punta Eugenia near 27N118W. Moderate to fresh NW to N winds persist through most of the Gulf of California, primarily over the central Gulf, with light to gentle breezes off the Pacific coast of Baja California. Farther south, outside of the Tehuantepec area, light to gentle winds are observed elsewhere over the open waters off Mexico with seas of 3-5 ft. Seas of 1-3 ft prevail in the Gulf of California. For the forecast, the high pressure will continue to dominate the offshore forecast waters of Baja California through Thu. The high pressure will dissipate ahead of a cold front that will approach to the northern Baja California by late Fri. This pattern will support fresh to strong westerly gap winds Fri night over the northern Gulf of California ahead of the front. Fresh winds and moderate NW swell will follow the front off Baja California as it moves across the region through late Sat, before stalling and dissipating over the southern Gulf of California Sun. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR Moderate to locally fresh NE winds are observed in the Gulf of Papagayo. Light to move eastward across the waters north of 20N over the next couple of days before dissipating. The swell event that follows the front will continue to propagate across the forecast area, with seas of 8-10 ft covering most of the region the N of 20N W of 125W by this afternoon, and N of 15N W of 125W by Wed afternoon. gentle winds are noted elsewhere north of the monsoon trough while gentle to moderate S to SW winds are seen south of the monsoon trough per recent scatterometer data. Seas are generally 3 to 5 ft across the offshore forecast waters. For the forecast, fresh gap winds will continue to pulse in the Papagayo region into mid week, then increase to 20 to 25 kt Wed night as high pressure builds north of region through Fri. Gentle to moderate breezes will persist elsewhere. No significant swell events are forecast during the next several days. REMAINDER OF THE AREA... Scattered showers and a few thunderstorms have dissipated near a 1011 mb low pressure centered near 19N130W. Recent scatterometer satellite data shows fresh to strong winds within 300 nm of the center of this low, and seas are estimated to be reaching 8 ft in this area. The low pressure is centered ahead of a cold front extending from 30N129W to 22N140W. Long period NW swell follows the front, and recent altimeter satellite data shows wave heights reaching 8 to 11 ft. Elsewhere, gentle to moderate winds persist, with 5 to 7 ft seas west of 120W primarily in NW swell, and 4 to 6 ft seas east of 120W. For the forecast, the low pressure will dissipate through tonight ahead of the approaching cold front. The cold front will stall tonight then dissipate through Thu, ahead of another frontal boundary approaching the areas from the northwest. The second, stronger front will reach from 30N123W to 22N135W Thu, then continue east and approach Baja California Fri. The large swell following the current front will subside into Thu, with moderate reinforcing swell following the second front. Looking ahead, additional reinforcing swell will move south of 30N Sun. No significant changes elsewhere. $$ Christensen