000 AXPZ20 KNHC 160405 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sat Dec 16 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 0000 UTC surface analysis and satellite imagery through 0345 UTC. ...SPECIAL FEATURES... Tehuantepec Gale Warning: Strong to neat gale force north to northeast winds are presently in the Gulf of Tehuantepec region and well to the southwest of the Gulf to near 11N98W. Seas are 8-10 ft within these winds. The gradient associated to 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. Northerly winds are forecast to increase to 30-40 kt with seas building to the range of 9-13 ft by Sat night into Sun morning. This gap wind event will continue well into next week, with winds briefly diminishing below gale force by Sun night into Mon, then increasing again to gale force Mon night through Wed night. Rough to very rough seas are expected. NW Eastern Pacific Gale Warning: A strong extratropical low pressure system is located north of the area near 34N137W. It is forecast to meander through Sun. A tight pressure gradient associated with this extratropical cyclone will remain in place over the northwest corner of the forecast area producing gale conditions and very rough to high seas through early Sat morning. The same low will continue to send a series of cold fronts into the northwest part of the area. A cold front presently extends from near 30N131W to 20N133W and to 14N140W. Gale force winds of 30-35 kt are north of 28N east of the front to 129W and north of 26N west of the front. Seas are 10-15 ft with the gale force winds east of the front and 8-12 ft with the gale force winds west of the front, with the exception of much higher seas of 14-20 ft in northwest swell north of 23N and west 132W. Winds elsewhere west of the cold front are west to northwest in direction at 20-30 kt. At 00Z ship with call letter ID "RCLKYXB" reported west winds of 30 kt near 26N138W. A second cold front will enter the forecast waters early this morning, while a third cold front is expected to reach the NW corner of the forecast area by Sat night. The 14-20 ft seas are due to a very large set of swell that is propagating through the northwest forecast waters in the wake of the first front. This is likely to lead to hazardous marine conditions. Seas are forecast to build to 18-24 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 and continues southwestward to 09N85W to 06N94W, where latest scatterometer data indicates that it transitions to the ITCZ and continues to 05N106W to 06N118W to 08N130W and to 10N140W. Scattered moderate to isolated strong convection is within 180 nm south of the trough between 81W-87W. Scattered moderate convection is within 60 nm either side of the ITCZ between 94W-103W and within 30 nm of the ITCZ between 105W-109W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section for details on an ongoing Gulf of Tehuantepec region gale warning. 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 well into 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 the middle of 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 earlier fresh to strong moderate to fresh northeast to east winds in the Gulf of Papagayo region, including the coast of southern Nicaragua have diminished to moderate to fresh speeds as the gradient has loosen up some. Seas with these winds are in the range of 4-6 ft. To the northwest of the Gulf of Papagayo region, seas of 6-8 ft in a northwest swell generated by the Gulf of Tehuantepec gap wind event are over the outer offshore waters of Guatemala and El Salvador. Gentle to moderate north winds and seas of 3-4 ft are in the Gulf of Panama, however, just to the southeast of the Gulf fresh to strong south winds are noted east of 79W to along the coast of Colombia. Seas are 4-6 ft with these winds. Scattered thunderstorms are along and just inland the coast of Colombia from 02N to 04N. For the forecast, the moderate to fresh northeast to east winds in the Gulf of Papagayo will increase back to fresh to strong beginning Sun night, and continue through the middle of next week while expanding to the southwest. These winds are expected to reach near gale force Tue night and Wed. Rough seas are expected over the Guatemala and El Salvador offshore waters 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. In addition, ship with call letter ID "VRFB3" reported south winds of 35 kt near 29N131W at 00Z. Please see the Special Features section for more details. Elsewhere, a N to S high pressure ridge offshore southern California and northern Baja California controls the gradient across the remainder of the forecast waters north of the ITCZ and west of 110W. Gentle to moderate trade winds are generally on both sides of the ITCZ/Monsoon trough with seas of 5-7 ft in mixed swell. For the forecast,the 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. $$ Aguirre