Tropical Weather Discussion

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Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0610 UTC. ...SPECIAL FEATURES... Central Pacific (EP90): An area of low pressure, Invest EP90, has fully crossed over into the Central Pacific basin to the west of 140W, currently near 11N141W. While outer winds and seas still extend just to the east of 140W into the discussion waters, winds east of 140W are forecast to remain below warning criteria. 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 just east of the area over portions of western Colombia and moving from the central to the western Caribbean Sea near 76W, moving westward at 15 to 20 kt. Scattered moderate isolated strong convection is noted from 06N to 11N between 77W and 89W. The axis of a tropical wave is near 96.5W from 01N to 17N just west of the Gulf of Tehuantepec over portions of Oaxaca, or a few hundred nautical miles south of the coast of southern Mexico, is moving westward at 15 to 20 kt. Scattered to numerous moderate to strong convection is noted from 05N to 14N between 89W and 98W. 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. The axis of a tropical wave is near 111W from 01N to 16N, moving westward at around 15 to 20 kt. A broad area of low pressure associated with this tropical wave near 08N111W is producing disorganized showers and thunderstorms several hundred nautical miles south of the southern tip of the Baja California Peninsula. Scattered to numerous moderate to strong convection is noted from 05N to 12N between 106W and 115W. Winds are currently fresh with locally rough seas there. Environmental conditions are forecast to be marginally favorable for gradual development over the weekend as the system moves westward or west- northwestward at 5 to 10 kt. Please refer to the latest NHC Tropical Weather Outlook at website: https://www.nhc.noaa.gov/text/MIATWOEP.shtml for more details on both systems. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 1007 mb low pressure over northern Colombia at 11N75W to 08.5N90W to 1009 mb low pressure near 08N111W to 07N125W to 10N140W. Other than the convection described above with three tropical waves, scattered moderate isolated strong convection is noted from 04N to 11N between 129W and 133W. Scattered moderate convection is noted from 10N to 17N between 130W and 140W, mainly related to Invest EP90 which has crossed over into the Central Pacific basin. ...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. A tight pressure gradient continues over the Gulf of Tehuantepec where the northern portion of a tropical wave is just passing by, and is producing strong N to NE gap winds in the Gulf. Recent ASCAT scatterometer data confirmed these winds. Resultant seas of 5 to locally 8 ft. Across the remainder of the offshore waters of Mexico, typical ridging has been disrupted by a surface trough from Baja California Norte to the southwest resulting in a rather weak pressure gradient across the region and mainly light to gentle winds, except moderate from near Cabo Corrientes up the coast toward the entrance of the Gulf of California as seen by the same ASCAT data. Seas are 4 to 6 ft across the waters away from the Gulf of Tehuantepec, and 1 to 3 ft inside the Gulf of California. A thunderstorm complex is evident on conventional infrared satellite imagery near the boast of western Oaxaca and Guerrero. For the forecast, northerly gap winds will continue to pulse to strong north winds over the Gulf of Tehuantepec during the overnight into the early morning hours 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. Winds may freshen across the Gulf of California Sat night through Sun night, and also freshen nearshore Baja California Fri night through Sat as the pressure gradient tightens a bit. Looking ahead, winds and seas are expected to build across the outer offshore waters of southwestern Mexico by tonight into early next week in association with a developing area of low pressure moving by just 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. Recent ASCAT scatterometer passes missed the immediate Gulf of Papagayo where fresh to strong easterly gap winds are likely occurring, however they did measure moderate to fresh easterly winds well downwind across the outer offshore waters of El Salvador and Guatemala to the south of 12.5N, with seas of 5 to locally 8 ft from Offshore Gulf of Papagayo to near 11N96W. Mainly moderate or weaker winds are found elsewhere, locally fresh near the border of Peru an Ecuador close to the entrance to the Gulf of Guayaquil. Seas are 4 to 7 ft across the remainder of the waters north of the Equator, and 6 to 8 ft south of the Equator, except to 9 ft near the Gulf of Guayaquil as measured by a recent Sentinel-3B altimeter pass. Some isolated to widely scattered showers and thunderstorms are over the waters south of Panama to off Costa Rica, as well as offshore Guatemala due to the passing tropical wave there, described more above. 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. Any lingering moderate to locally fresh southerly winds south of the monsoon trough and across the Galapagos waters will gradually diminish today. Mainly moderate seas will prevail away from the Gulf of Papagayo area through the next several days, dominated by long period southerly swells. Seas may be locally rough south of the Equator early today. ...REMAINDER OF THE AREA... Please see the Special Features section and the Tropical Waves section above for information on 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 which was nicely evident in a recent ASCAT scatterometer pass. Outer fresh to strong winds and 8 to 11 ft seas associated with Invest EP90 now west of the area in the Central Pacific basin are impacting the waters from 11N to 16N between 137W and 140W. Moderate to locally fresh trades are found elsewhere from 14N to 23N between 128W and 140W. Moderate to locally fresh winds are found south of 06N to the east of 120W and south of 02N to the west of 120W. Rough seas over the southern waters are decaying, now over the waters south of 02N and east of 130W, up to 9 ft south of the Equator and east of 110W. For the forecast, regardless of tropical development, the features described above will bring some increasing winds and seas to area waters south of 25N, as they move south of the current ridge in place. 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 fully subside to moderate levels by the start of the weekend.