Eastern Pacific Tropical Weather Discussion
552 AXPZ20 KNHC 200256 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Thu Aug 20 2026 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 0130 UTC. ...SPECIAL FEATURES... Central Pacific (EP90): A broad area of low pressure, Invest, EP90, is located well to the east-southeast of the Hawaiian Islands near 10.5N140W. Associated winds are currently 20 to 30 kt and seas are 8 to 10 ft. This low is along a tropical wave at 140W. The system is producing showers and thunderstorms that are gradually becoming better organized. Scattered to numerous moderate to strong convection is noted from 03N to 16N between 131W and 140W. Environmental conditions appear favorable for further development of this system, and a tropical depression is likely to form during the next day or so while the disturbance moves westward to west-northwestward at 10 to 15 mph and crosses into the Central Pacific tonight. Interests in the Hawaiian Islands should closely monitor the progress of this system. This system has a high chance of tropical cyclone formation in the next 48 hours. Interests in the Hawaiian Islands should closely monitor the progress of this system. Please refer to the latest NHC Tropical Weather Outlook at website: https://www.nhc.noaa.gov/text/MIATWOEP.shtml for more details. ...TROPICAL WAVES... The axis of a tropical wave is near 95.5W from 02N to 16N near the western Gulf of Tehuantepec, moving westward at 15 to 20 kt. Scattered to numerous moderate to strong convection is noted from 09N to 13N between 92W and 99W. The axis of a tropical wave is near 109W south of 17N, moving westward at 10 kt. Scattered moderate isolated strong convection is noted from 07N to 15N between 101W and 113W. An area of low pressure is expected to form several hundred nautical miles south-southwest of the coast of southern Mexico around the end of the week. Gradual development of this system is likely thereafter, and a tropical depression is likely to form this weekend while the system moves generally west-northwestward, remaining well offshore of Mexico. This system has a low chance of tropical cyclone formation in the next 48 hours, and a high chance in the next 7 days. Regardless of development, expect increasing winds and seas to impact the outer offshore waters of southwestern Mexico. Please refer to the latest NHC Tropical Weather Outlook at website: https://www.nhc.noaa.gov/text/MIATWOEP.shtml for more details. The axis of a tropical wave is near 140W, and is described above in the Special Features section above regarding the possibility of tropical cyclone formation. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 1007 mb low pressure over northern Colombia at 10N74W to 08N91W to 1006 mb low pressure near 09N110W to 06N122W to low pressure, Invest EP90, near 10.5N140W. Other than the convection described above with three tropical waves, scattered moderate isolated strong convection is noted from 03N to 08N between 77W and 94W, from 10N to 17N between 99W and 107W, from 03N to 07N between 113W and 132W, and from 07N to 14N between 122W and 131W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Tropical Waves section above for information on a tropical wave that has a potential for tropical development offshore Mexico this upcoming weekend, and for related convection. High pressure across the NE Pacific extends a ridge south- southeastward into the regional waters to just northwest of the Revillagigedo Islands. The pressure gradient over the waters from southwestern Mexico to Baja California has weakened today, allowing for moderate or weaker winds across those waters, including in the Gulf of California, except lingering fresh winds in the northern Gulf. Meanwhile, a tight pressure gradient continues over the Gulf of Tehuantepec where the northern portion of a tropical wave is moving by, and is producing strong N to NE gap winds in the Gulf. Resultant seas of 5 to 7 ft are present there. Seas are 4 to 6 ft across the remainder of these offshore waters, and 1 to 3 ft inside the Gulf of California. For the forecast, northerly gap winds will continue to pulse to strong north winds over the Gulf of Tehuantepec each evening and night through the next several days, with seas occasionally building to rough. Low pressure across Baja California will sustain a southerly wind flow across the Gulf of California waters, with fresh winds expected across northern portions there gradually diminishing later tonight. Winds may freshen across the Gulf of California Sat night through Sun night. Looking ahead, winds and seas are expected to build across the outer offshore waters of southwestern Mexico by Fri into the upcoming weekend in association with a developing area of low pressure, expected to develop outside of the offshore waters. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Refer to the Tropical Waves section above for details on any convection. Fresh to locally strong easterly gap winds continue across the Papagayo region. Seas there are 5 to 8 ft with these winds, with the highest seas extending well downwind to near 11N92W where moderate to fresh winds also extend to. Winds are moderate or weaker elsewhere north of the monsoon trough, and moderate south of the monsoon trough, except moderate to fresh south of the Equator, highest near the entrance of the Gulf of Guayaquil where they are locally strong2. Seas across most of the remainder of the waters north of the Equator are 4 to 6 ft in mixed cross equatorial S and SW swell, and 7 to 9 ft in S to SW swell south of 02N, highest south through southwest of the Galapagos Islands. For the forecast, the pressure gradient between high pressure over the northwestern Caribbean and relatively lower pressure over Central America will lead to fresh NE to E gap winds pulsing to strong winds over the Papagayo region each evening and night through the early next week, resulting in rough seas at times. Moderate to fresh winds extending well downwind of Papagayo will impact the outer waters offshore of El Salvador and Guatemala through at least early next week. Moderate to locally fresh southerly winds south of the monsoon trough and across the Galapagos waters will gradually diminish tonight through Thu, then remain gentle to moderate through the weekend. Cross- equatorial SW swell moving into the regional waters will continue to merge with larger S to SE swell dominating the southern Pacific waters well south of the Galapagos to produce rough seas 8 ft and greater south of 02N, and moderate seas elsewhere through Thu before seas subside. ...REMAINDER OF THE AREA... Please see the Special Features section and the Tropical Waves section above for information on two systems that have the potential for tropical cyclone formation, and any associated convection currently present leading to locally higher winds and seas. High pressure across the NE Pacific extends a ridge south- southeastward into the regional waters to just northwest of the Revillagigedo Islands, however it is now disrupted by a surface trough analyzed from 30N135W to 23N140W. Away from Invest EP90 along 140W and exiting into the Central Pacific basin, moderate to fresh winds are near a 1006 mb low pressure at 09N110W along a tropical wave at 110W, from 10N to 14N between 108W and 112W where seas are locally rough. Moderate to fresh NE to E winds extend well downwind from a Gulf of Papagayo gap wind event to near 10N100W. Seas are locally rough there as well. Winds are moderate or weaker across the remainder of the waters, except moderate to fresh south of 06N. Seas are 8 to 10 ft near Invest EP90, and 4 to 6 ft elsewhere north of 12N, 6 to 8 ft from 07N to 12N, and 7 to 9 ft in mixed SE and SW swell south of 07N. For the forecast, regardless of tropical development, the features described above will bring some increasing winds and seas to area waters south of 20N, as they move south of the current ridge in place. Invest EP90 near 140W will move away from the waters into the Central Pacific basin through Thu. Away from these features, little change is expected in marine weather through the next several days, except for the rough seas over the southern waters which are forecast to subside by the start of the weekend.