000 AXPZ20 KNHC 180353 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Mon Dec 18 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... Gulf of Tehuantepec Gale Warning: The pressure gradient between high pressure along the eastern slopes of Mexico and the eastern north Pacific monsoon trough is supporting gale-force north to northeast winds of 30-40 kt in the Gulf of Tehuantepec, with seas in the 9-13 ft range. A tight pressure gradient will support gale conditions through much of the week. Seas with this latest gale-force gap wind event are forecast to peak near 14 ft on Tue. Eastern Pacific Significant Swell event: A deep extratropical low pressure system is located north of the area near 36N134W with pressure of 992 mb. Since the low has pulled far enough away from the discussion area, the very tight pressure gradient of the past few days has slacken considerably. Only a small area of fresh to strong southwest to west winds remains north of 29N and between 129W-133W along with seas of 12-16 ft in NW swell. Elsewhere, seas of 12 ft generated from the gale event of the past few days are over the western part of the area north of 17N and west of about 130W. These seas are maxing out at 14 ft. These seas will subside tonight, lowering to below 12 ft on Mon. 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 northwestern Colombia to across western Panama and to 09N83W to 06N99W. The ITCZ extends from 06N99W to low pressure near 07N110W 1007 mb to 07N121W to 06N132W and to 07N140W. Numerous moderate to strong convection is within 60 nm either side of the ITCZ between 120W and 127W. Scattered moderate isolated strong convection is within 60 nm either side of the ITCZ between 115W and 120W. Scattered moderate convection is within 60 nm north of the ITCZ between 105W and 110W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for details on an ongoing Gulf of Tehuantepec Gale Warning. Aside from the Gulf of Tehuantepec, moderate northwest winds, and seas of 1-3 ft, are over the Gulf of California. A weak pressure gradient dominates the Mexican offshore waters outside of the Gulf of Tehuantepec, with moderate or weaker winds across the rest of the offshore waters. Seas are in the 4-7 ft range in long- period west to northwest swell off Baja California Norte, and 4-5 ft elsewhere. For the forecast, moderate northwest winds over the Gulf of California will gradually diminish through the week. Large NW swell will reach the outer offshore forecast waters of Baja California between Cabo San Lazaro and Punta Eugenia tonight, then subside on Tue. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh northeast to east winds, and seas of 4-5 ft, are over and downstream of the Gulf of Papagayo region. Northwest swell generated by the Gulf of Tehuantepec gale-force gap wind event is supporting seas in the 7-9 ft range over the outer offshore waters of Guatemala and El Salvador. Moderate to fresh north winds and seas of 3-5 ft are over the Gulf of Panama. Moderate to fresh north winds and seas of 3-5 ft are elsewhere across the discussion waters. For the forecast, moderate to fresh northeast to east winds in the Gulf of Papagayo will increase to fresh to strong early this week. The fresh to strong winds will continue through the week, reaching near gale force Mon night through Wed. NW swell generated by the Gulf of Tehuantepec gale-force gap wind event will impact the outer Guatemala and El Salvador offshore waters for much of the week. The moderate to fresh north winds over the Gulf of Panama are expected to continue well into the week, reaching strong speeds Mon night through early Wed. Elsewhere, winds are expected to be moderate or weaker for the next several days. ...REMAINDER OF THE AREA... Please see above for details on a significant swell event over the western portion of the basin. A 992 mb low pressure system is located north of the discussion area near 36N134W. Since the low has pulled far enough away from the area, the very tight pressure gradient of the past few days has weakened considerably. Only a small area of fresh to strong southwest to west winds remains north of 29N and between 129W-133W. Moderate to fresh winds are elsewhere north of 24N and west of 125W. Moderate to fresh winds are north of the ITCZ to near 15N. Gentle to moderate winds are south of the monsoon trough. Light to gentle winds are elsewhere over the discussion waters. Outside of the area of 12 ft seas, seas greater than 8 ft are found over much of the waters north of 07N and west of 122W. Seas of 5-7 ft prevail elsewhere over the discussion waters. For the forecast, winds south of the ITCZ will be in the moderate to fresh range through Mon. Swell from the Tehuantepec gap wind event will spread westward, with seas of 8-9 ft reaching to near 104W tonight before starting to subside. The 8 ft seas from the northwest swell over the western waters will spread eastward to cover much of the waters west of 120W on Mon before starting to subside below 8 ft. A new set of northwest swell will move into the northwest waters at midweek. Seas with this swell will peak near 15 ft over the northern waters early Thu before starting to subside. $$ Aguirre