000 AXPZ20 KNHC 132159 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Wed Dec 13 2023 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 2130 UTC. ...SPECIAL FEATURES... Tehuantepec Gale Warning: Strong high pressure over the Gulf of Mexico continues to force gale- force gap winds over the Gulf of Tehuantepec. Scatterometer data depicted these gale force winds this afternoon extending as far south as 14N. The strong winds extend farther south likely to near 11N. Peak seas are around 15 ft. The 8 ft seas extend west- southwestward to 05N105W. The gale- force winds will end Thu night into early Fri morning. Strong winds will persist through the weekend. Seas will subside below 12 ft by Fri morning. NW Eastern Pacific Gale Warning: A weak cold front is approaching the northwest waters of the tropical eastern Pacific. A reinforcing cold front will arrive to the area on Thu, triggering the formation of a large extratropical cyclone that will approach the NW corner of our waters late Thu. Strong to gale S-SW winds are forecast ahead of its associated cold front. After the front reaches the NW corner on Thu night, near gale to gale W to NW winds behind the front should occur north of 25N and west of 123W through Fri night into early Sat. Very large NW swell will be accompanying this system with seas over 20 ft through Sun. The 12 ft seas will through the weekend, extending as far south as north of 18N and as far east as 129W. Please read the latest High Seas Forecast and the Offshore Waters Forecast issued by the National Hurricane Center at https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and www.nhc.noaa.gov/marine/offshores.php for details on the special feature. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from the coast of Costa Rica near 09N84W to 06N92W. The ITCZ extends from 06N92W to 06N106W to 09N119W and then from 07N128W to beyond 08N140W. Scattered moderate isolated strong convection is noted from 04N to 12N between 92W and 124W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the SPECIAL FEATURES section for details on a Gale Warning for the Tehuantepec region. A weak pressure gradient across the Baja California offshore waters is sustaining gentle to moderate NW winds. Seas range 4 to 5 ft mostly within NW swell and some easterly swell from the influence of the Gulf of Tehuantepec gap wind event. Scatterometer confirmed light to gentle winds prevailing in the Gulf of California with smooth seas. In the southwest Mexico offshore waters, outside of the Gulf of Tehuantepec, scatterometer depicted light to gentle variable winds prevail with seas 4 to 6 ft within mixed E and SE swell. No significant convection is noted at this time. For the forecast, high pressure will build over the U.S. Great Basin late this week. This will result in fresh to strong NW winds over the Gulf of California starting on Thu night through Fri night. Looking ahead, a new gale-force gap wind event over the Gulf of Tehuantepec is expected to begin on late Sat and continue into early next week. Rough seas can be expected with these winds. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Surface ridging from a 1037 mb high pressure system over the SE United States extends across the Gulf of Mexico and NW Caribbean Sea. This is interacting with lower pressures in the deep tropics, and the resulting pressure gradient is sustaining persistent fresh to strong NE-E gap winds across the Gulf of Papagayo region. Seas in these waters are 7-9 ft. Northerly swell producing seas of 8-11 ft generated by the Gulf of Tehuantepec gap wind event continues to affect the offshore waters of Guatemala and El Salvador. Scatterometer data depicted moderate northerly winds and seas likely range 3 to 4 ft in the Gulf of Panama. Meanwhile, gentle to moderate southerly winds are noted south of 03N. Seas in these waters are 4-6 ft in a mixed swell. Elsewhere, light to gentle winds and slight to moderate seas prevail. For the forecast, the strong NE winds in the Gulf of Papagayo are expected through Fri, diminishing to moderate to fresh this weekend. Peak seas will be near 10 ft Wed through Thu. The large NW swell over the Guatemala and El Salvador offshore waters will only gradually diminish through Thu night. Expect another round of rough seas in this area due to another Gulf of Tehuantepec gap wind event on Sun. Elsewhere, winds are moderate or weaker for the next several days. ...REMAINDER OF THE AREA... Please see the Special Features section for more information on the gale warnings for the northwest waters of the area. A 1022 mb high pressure system centered near 31N131W extends southeastward to the Revillagigedo Islands. Moderate to fresh easterly trade winds are noted N of the ITCZ to 22N according to the latest scatterometer data. Seas in these waters are 5-9 ft. Large 8-10 ft NW to N swell being produced by the Gulf of Tehuantepec gap wind event extends equatorward to 05N and westward to 112W. A 1011 mb low pressure is noted near 09N122W with a trough extending along the low from 12N119W to 08N127W. Scattered moderate convection is noted around this low with moderate to fresh winds. Meanwhile, a weakening cold front is approaching the northwest corner of the basin and no deep convection is associated with this feature. Elsewhere, moderate or weaker winds and moderate seas are prevalent. For the forecast, trade winds will slowly diminish to be moderate or weaker by Fri and continue through the weekend as the extratropical low moves across the area. Large swell from the extratropical low will impact most of the waters, with the 8 ft seas extending as far south as the equator and as far east as 100W. A new gale event across the Gulf of Tehuantepec will bring rough waters to the high seas later on Sun and into Mon, extending towards 10N100W. $$ AReinhart