392 AXPZ20 KNHC 152139 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Fri Dec 15 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 2100 UTC. ...SPECIAL FEATURES... Tehuantepec Gale Warning: Recent satellite derived wind data indicate fresh to strong N to NE winds in the Gulf of Tehuantepec and downwind to about 11N98W. Seas are 8 to 11 ft within these winds. A developing low pressure area over the Gulf of Mexico will bring fresh to strong northerly winds over the western part of the Gulf. These winds will support the return of gale force winds in the Gulf of Tehuantepec by Sat afternoon. Wind are forecast to increase to 30 to 40 kt with seas building to 13 to 14 ft by Sat night into Sun morning. This gap wind event will continue into early next week, with winds briefly diminishing below gale force by Sun night into Mon, then increasing again to gale force Mon night through Tue night. Rough to very rough seas are expected. NW Eastern Pacific Gale Warning: A strong low pressure system will remain nearly stationary N of region near 34N138W through Sun. A tight pressure gradient associated with this extratropical cyclone will remain in place over the NW corner of the forecast area producing gale conditions and very rough to high seas through early Sat morning. The same low will bring two or three fronts. The first front extends from 30N132W to 14N140W. Gale force winds are on either side of the front N of 28N. A secondary front will enter the forecast waters tonight while a third cold front is expected to reach the NW corner of the forecast area by Sat night. A very large swell event is propagating across the northwest forecast waters with seas of 12 to 20 ft in the wake of the main front creating hazardous marine conditions. Seas are forecast to build to 18 to 24 ft behind the third cold front by early Sat afternoon. A that time, the leading edge of the 12 ft and greater seas will reach as far south as 18N and west of about 126W. Seas will begin to slowly subside starting Sun afternoon and into early next week. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northern Colombia near 10N75W to 09N85W to 05N100W. The ITCZ continues from 05N100W to 07N120W to beyond 09N140W. Scattered moderate to isolated strong convection is noted from 03N to 08N between the coast of Colombia and 110W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section for details on a Gale Warning for the Gulf of Tehuantepec region. The combination of high pressure over the U.S. Great Basin and relatively lower pressure over northwest Mexico and the Gulf of California area is allowing for fresh to strong northwest to north winds over the entire Gulf of California with seas to 6 ft. These winds are spilling out of the Gulf reaching as far south as the waters between Cabo Corriente and 109W. Meanwhile, weak pressure gradient dominates the Mexican offshore waters, outside of the Gulf of Tehuantepec. Moderate or weaker winds and slight to moderate seas continue across the rest of the offshore waters. Seas across the Baja California offshore waters and over the southern Mexico offshore waters are in the 4-6 ft range due to long-period west to northwest swell. No significant convection is presently noted over these waters. For the forecast, a gap wind event is ongoing in the Tehuantepec region, and it is forecast to persist into early next week. Strong to near-gale force northerly gap winds will continue through Sat morning, before increasing back to gale force in the afternoon. These winds are forecast to remain at gale force speeds into early next week. Rough to very rough seas can be expected with these winds. Meanwhile, high pressure will build over the Great Basin in the western United States through Sat. The associated gradient will maintain fresh to strong northwest winds over the Gulf of California through late tonight, then diminish Sat through Sun night. Building seas of 6 to 8 ft associated with a large swell event will reach the outer offshore forecast waters of Baja California between Cabo San Lazaro and Punta Eugenia by Sun night. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The combination of a strong high pressure N of the area and relatively lower pressure found south of Mexico is maintaining fresh to locally strong trade winds in the Gulf of Papagayo region, including the coast of southern Nicaragua. These winds extend SW to near 09.5N88W. Seas with these winds are in the range of 5 to 8 ft. In addition, seas of 6 to 8 ft in a northwest swell generated by the Gulf of Tehuantepec gap wind event are noted over the outer offshore waters of Guatemala and El Salvador. Gentle to moderate N winds and seas of 2 to 4 ft are in the Gulf of Panama. For the forecast, the fresh to locally strong northeast to east winds in the Gulf of Papagayo will diminish to moderate to fresh speeds by early this evening. These winds will increase back to fresh to strong beginning Sun night, and continue through mid week while expanding to the southwest. Swell over the Guatemala and El Salvador offshore waters will subside below 8 ft by early this evening. Expect rough seas in this area once again for Sun and Sun night due to another Gulf of Tehuantepec gap wind event that begins on Sat. Elsewhere, winds are moderate or weaker for the next several days. ...REMAINDER OF THE AREA... A strong extratropical cyclone is affecting the NW corner of the forecast region producing gale-force winds and very large seas. Recent scatterometer data confirmed the presence of the gale- force winds while an altimeter pass indicated seas to 15 ft. Please, see the Special Features section for more details. Elsewhere, high pressure of 1021 mb located offshore southern California dominates the remainder of the forecast waters N of the ITCZ W of 110W. Gentle to moderate winds are generally on both sides of the ITCZ/Monsoon trough with seas of 5 to 7 ft in mixed swell. For the forecast, trade winds will slowly diminish to be moderate or weaker through the weekend as the gradient slackens in response to frontal systems moving into the northwest part of the discussion area. $$ GR