000 AXPZ20 KNHC 160234 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Mon Oct 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 0230 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A cold front is moving across the Gulf of Mexico with high pressure building across eastern Mexico in its wake. The pressure gradient between the area of high pressure and the eastern north Pacific monsoon trough is supporting strong to near gale- force gap winds, and seas to 8 ft, in the Gulf of Tehuantepec. The pressure gradient will further tighten, with gale- force winds expected to begin tonight. Seas will peak near 15 ft Mon night as winds peak near 40 kt. The area of high pressure will start to shift eastward. This will loosen the pressure gradient which will help diminish winds below gale-force Tue night into Wed morning. Meanwhile, seas will subside below 12 ft by Tue night. The pressure gradient will remain tight enough to support pulsing fresh to strong winds through the remainder of next week. Please read the latest NHC High Seas Forecast at website www.hurricanes.gov/marine for more details. South of Southwestern Mexico (EP90): A broad area of low pressure is producing disorganized shower and thunderstorm activity extending several hundred miles south of the southern coast of Mexico. Winds associated with a Gulf of Tehuantepec gale- force gap wind event, mentioned above, will help generate spin for the developing area of low pressure. Environmental conditions are conducive for development of this system, and a tropical depression is expected to form in a few days while moving slowly westward and then northwestward well offshore of the coast of southwestern Mexico. This system has a medium chance of development in 48 hours and high chance in 7 days. Please see hurricanes.gov for the latest NHC Tropical Weather Outlook. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 11N86W to low pres near 12N100W to 08.5N121W to 10N140W. Scattered moderate convection is noted from 04N to 17N E of 106W, and within 120 nm south of the monsoon trough between 115W and 140W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see SPECIAL FEATURES section above for more on the upcoming Gulf of Tehuantepec gale- force gap wind event and the system south of southwestern Mexico that is being monitored for TC development. Aside from the Gulf of Tehuantepec and EP90, a ridge extends across the Baja California offshore waters. Gentle to moderate winds prevail west of the Baja California peninsula as well as the Gulf of California. Light to gentle winds are noted off SW Mexico. Seas are in the 5-7 ft range over the open waters off Mexico, and 3-4 ft over the Gulf of California. For the forecast, strong to near gale- force gap winds across the Gulf of Tehuantepec will reach gale- force tonight then diminish below gale- force Tue night into Wed morning. Fresh to strong winds will continue to pulse over the Tehuantepec region through the remainder of the week. Rough to very rough seas can be expected over this area through Wednesday. Gentle to moderate winds west of the Baja California peninsula and over Gulf of California will continue through Tuesday night before diminishing. Elsewhere, a broad area of low pressure is producing disorganized shower and thunderstorm activity extending several hundred miles south of the southern coast of Mexico. Environmental conditions are conducive for development of this system, and a tropical depression is expected to form in a few days while moving slowly westward and then northwestward well offshore of the coast of southwestern Mexico. This system has a medium chance of development in 48 hours and high chance in 7 days. Looking ahead, another area of low pressure is expected to form south of the coasts of Guatemala and southern Mexico by the middle of the week. Gradual development of the disturbance will be possible, and a tropical depression could form late this week as the system meanders over the far eastern portion of the basin. This system has a low chance of formation in 48 hours and a medium chance in the next 7 days. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds are noted N of the monsoon trough, with gentle to locally moderate winds S of the monsoon trough. Seas range 5 to 6 ft across the discussion waters in subsiding southerly swell. For the forecast, seas will increase moderate to rough on Mon and Tue well offshore of Guatemala and El Salvador from swell generated from the Gulf of Tehuantepec gale- force gap wind event. Light to gentle winds will prevail north of the monsoon trough through Mon. Winds will pulse moderate to fresh near the Gulf of Papagayo Tue through Wed night. Gentle to moderate winds will prevail south of the monsoon trough. Long- period southerly swell will slowly subside across the area through Mon. Looking ahead, an area of low pressure is expected to form south of the coasts of Guatemala and southern Mexico by the middle of the week. Gradual development of the disturbance will be possible, and a tropical depression could form late this week as the system meanders over the far eastern portion of the basin. This system has a low chance of formation in 48 hours and a medium chance in the next 7 days. ...REMAINDER OF THE AREA... A 1019 mb high pressure center near 27N128W extends a ridge to near the Revillagigedo Islands. A cold front is approaching 30N140W. The pressure gradient between these features is supporting moderate to fresh winds over the waters N of 28N and W of 132W. Gentle to moderate winds are noted elsewhere. NW swell propagating across the NW waters is bringing seas of 8-10 ft over the NW waters. Elsewhere, seas of 5-7 ft prevail. For the forecast, The cold front will not move too far into the discussion waters before stalling and dissipating. However, the NW swell generated by the front will continue propagating southward through the middle of next week. By Tue night into Wed, a large set of NW swell generated by a hurricane force low near 45N173W is expected to move into the NW waters, with seas peaking near 15 ft on Wed. Seas greater than 8 ft associated to this swell will cover much of the discussion waters W of 110W by the end of the week. Southerly swell will propagate northward into the discussion waters S of 01N between 97W and 120W by the end of the week. $$ AL