000 AXPZ20 KNHC 201547 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Nov 20 2024 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A gap wind event will develop in the Gulf of Tehuantepec today following a strong cold front that will progress southeastward across the western Gulf of Mexico. The tightening pressure gradient between building high pressure over Mexico and low pressure off the southwestern coast of Mexico will support strong N winds later this afternoon with gale force winds quickly following this evening. Strong gales will be possible early Thu through Thu night. Rough seas will occur across the Gulf of Tehuantepec this evening through this weekend, with very rough seas likely in the area of strongest wind. Seas will peak around 15 ft Thu through Thu night. Gale force winds will end Sat morning with strong winds ending by early Sun morning. Seas will fall below 12 ft by Fri night and below 8 ft by Sat night. For more details, 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 16N94W to 08N120W. The ITCZ continues from 08N120W to beyond 09N140W. Scattered moderate convection is observed from 12N to 15N between 92W and 98W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section for information on the upcoming Gulf of Tehuantepec Gale event. A 1021 mb high is centered near 31N121W, and ridging extends across the Baja California offshore waters. This pattern supports gentle to moderate NW winds across the Baja California waters and areas offshore of southwestern Mexico. A long-period N to NW swell continues to produce rough seas to off Punta Eugenia and to about 120 nm off the coast of Cabo San Lazaro, with peak seas to 10 ft. Meanwhile, the pressure gradient between the ridge of high pressure and troughing over NW Mexico is supporting moderate to fresh NW winds in the Gulf of California, and locally strong winds in the central Gulf, as confirmed by earlier scatterometer satellite data. Seas of 3 to 5 ft are noted in this area. Farther south, fresh to locally strong SW winds were noted earlier in scatterometer satellite data off western Oaxaca and Guerrero, with associated rough seas. This was related to a low pressure area along the monsoon trough, which has since dissipated allowing the winds to diminish. Residual shorter period swell to 8 ft persists, but is subsiding. For the forecast, a cold front moving across the western Gulf of Mexico and into southern Mexico will support gale force winds and rough seas across the Gulf of Tehuantepec starting this evening and persisting into early Sat, with strong gales and very rough seas likely Thu and Thu night as high pressure builds north of the area behind the front. These gales and rough seas will reach beyond 300 nm downstream of the Gulf of Tehuantepec into early Sat. Rough seas off western Oaxaca and Guerrero will subside through this afternoon. Farther north, large NW swell off Baja California will expand southward to 20N by tonight then subside. Another long- period N swell will reinforce rough seas offshore of Baja California Norte on Thu before seas subside on Fri. Fresh to locally strong NW winds will pulse in the central and southern Gulf of California through Thu. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate SW winds are occurring offshore of Guatemala and El Salvador, where seas of 5 to 7 ft are noted. Gentle to locally moderate S to SW winds and seas of 4 to 6 ft prevail across the remainder of the Central and South American offshore waters. For the forecast, fresh to strong N to NE winds and very rough seas associated with a Gulf of Tehuantepec gap wind event will affect the far western Guatemala offshore waters early Thu through Fri. Fresh to strong E to NE winds will then pulse in the Gulf of Papagayo Fri and Sat. Moderate winds and seas will persist otherwise through late Sun. ...REMAINDER OF THE AREA... A 1021 mb high is centered near 31N121W, and ridging extends across the waters north of 20N. Moderate to fresh SW winds are noted between the high pressure and a cold front approaching from the northwest. Mostly moderate trade wind flow is noted south of the ridge, west of 110W. NW swell of 7 to 10 ft dominates the waters north of 20N. Pockets of 7 to 8 ft seas are noted along the monsoon trough, in a combination of NW and SW swell, along with shorter-period NE seas due to trade wind flow. Farther east, rough seas to 8 ft linger well off the coast of southern Mexico, where fresh to strong winds were active earlier but have since diminished. Moderate winds and seas persist elsewhere. For the forecast, the high pressure will weaken but shift southward, anchored by 1020 mb high pressure near 25N130W Sat. This will mostly block a cold front to the north of region. This pattern will support periods of fresh to strong SW winds north of 25N and west of 130W Thu and Fri. The NW swell will continue to propagate southward while decaying through late Thu, reinforcing the ongoing swell along the monsoon trough into Sun. Another round of NW swell will cover the region north of 25N and west of 125W Fri and Sat before subsiding. Looking ahead, a complex wave pattern will develop by Sun over the tropical eastern Pacific from 05N to 10N between 105W and 115W in a mix of NW and SW swell, along with a component of shorter period NE swell generated by the Tehuantepec gap wind event. $$ Christensen