000 AXPZ20 KNHC 152201 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sun Oct 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 2130 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 fresh to strong gap winds in the Gulf of Tehuantepec. Seas are currently around 8 ft near these winds. The pressure gradient will continue to tighten today, 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 and loosen the pressure gradient. Winds will diminish below gale-force by Tue night into Wed morning as a result. Meanwhile, seas will drop 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: Showers and thunderstorms located southwest of the Gulf of Tehuantepec are associated with a trough of low pressure. This system is forecast to move slowly westward to west-northwestward, and an area of low pressure is expected to form several hundred miles south of the southwestern coast of Mexico in a day or two. Further development of the system is likely, and a tropical depression is expected to form during the middle to latter part of the week while the system meanders well offshore of the coast of 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 off the coast of Costa Rica near 10N86W to 08N110W to 07N130W to beyond 11N140W. Scattered moderate to isolated strong convection is noted from 07N to 17N between 80W and 106W. Scattered moderate convection is noted from 04N to 16N between 113W and 140W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see SPECIAL FEATURES section above for more in the upcoming Gulf of Tehuantepec gale- force gap wind event and the system south of southwestern Mexico that is being monitored. Aside from the Gulf of Tehuantepec, a ridge extends across the Baja California offshore waters. Moderate to locally fresh N to NW winds prevail in the Gulf of California with seas to 4 ft. Gentle to moderate winds prevail across the Baja California offshore waters with seas ranging 5 to 7 ft within NW swell. Light to gentle winds prevail across the rest of the Mexico offshore waters. Seas range 4 to 6 ft in mixed swell. Thunderstorms continue across the Oaxaca and Guerrero offshore waters. For the forecast, fresh to strong 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. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds are noted N of 07N in the Central American offshore waters with seas 5 to 6 ft in S to SW swell. Gentle to moderate S winds are noted across the rest of the offshore waters S of 07N. Seas range 5 to 6 ft across these waters in S swell. Scattered showers are noted across the Central American and Colombian offshore waters. 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 El Salvador 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... Ridging extends across the northern waters to 20N. A cold front is W of the area, and scatterometer depicts moderate to locally fresh SW winds N of 27N and W of 130W. This area is also seeing NW swell from this system, bringing 8 to 9 ft seas. Elsewhere across the waters, winds are gentle to moderate N of the monsoon trough 5 to 7 ft, Gentle to moderate winds are also noted south of the monsoon trough with seas ranging 5 to 7 ft. For the forecast, the NW swell will continue propagating southward through the middle of next week. By Tue night into Wed, a large set of NW swell 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 in the southern waters S of 01N between 97W and 120W will also push northward into the area later in the week. $$ AReinhart