Tropical Weather Discussion

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Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Mon May 18 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Significant Swell Event West of Baja California Norte: Very large, long-period NW swell is maintaining very rough seas of 12 to 15 ft, north of 26N between 117W and 127W, including waters near Guadalupe Island. This swell will gradually decay and retreat northward through late Tue, which should allow seas to subside below 12 ft by late this evening. Please refer to the latest High Seas and Offshore Waters Forecasts issued by the National Hurricane Center at websites: https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and https://www.nhc.noaa.gov/marine/offshores_eastpac.php for more details. ...TROPICAL WAVES... A tropical wave is near 81W from the western Caribbean Sea southward across Panama into the eastern Pacific, and moving west at 5 to 10 kt. It is enhancing convection near the monsoon trough described in the section below. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A monsoon trough extends west-southwestward from central Costa Rica to 07N96W. An ITCZ continues westward from 07N96W to 07N120W to beyond 08N140W. Scattered moderate to strong convection is active near and south of the monsoon trough from 02N to 08N east of 87W, including offshore waters of Costa Rica, Panama and Colombia. Scattered moderate convection is seen near the ITCZ and rest of the monsoon trough from 03N to 11N between 90W and 99W. Numerous moderate to scattered strong convection is present near the western part of the ITCZ from 01N to 11N west of 120W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please read the Special Features section above regarding Significant NW swell. Low pressure is moving eastward over the Colorado River Valley in between higher pressure over the eastern Pacific and northwest Mexico. This pattern is supporting strong to near-gale force SW gap winds across the northern Gulf of California. These winds have diminished slightly from gale-force winds earlier this evening. Moderate to rough seas are associated with these gap winds across the northern Gulf. The pattern is also supporting fresh NW winds off Baja California Norte, as noted in recent scatterometer satellite data. Concurrent altimeter satellite and Sofar buoy data confirmed the large swell off Baja California mentioned in the Special Features section, with 10-13 ft combined seas north of Cabo San Lazaro. Gentle breezes are noted elsewhere. Seas are 6-9 ft off Baja California off Baja California Sur south of Cabo San Lazaro, 4-6 ft elsewhere off southern Mexico, and 1-3 ft over the central and southern Gulf of California. For the forecast, a trough moving across the Colorado River Valley and higher pressure over northwestern Mexico and the eastern Pacific are altogether supporting fresh SW to NW gap winds in the northern Gulf of California this morning. This is also supporting moderate to fresh NW winds off Baja California Norte. Winds in both areas will subside to between gentle and moderate later this afternoon. In addition, very large and long- period NW swell will maintain very rough seas off Baja California Norte through this afternoon, then subside to rough this evening through Tue. Rough seas will also linger near Baja California Sur through Tue. Gentle to moderate winds and moderate seas will persist elsewhere through Fri. ....OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... A recent scatterometer satellite pass indicated fresh gap winds downwind of the Gulf of Papagayo, and north of a broad circulation along the monsoon trough centered near 09N88W. Gentle breezes and 3-5 ft seas are noted elsewhere primarily with SW swell. Scattered showers and thunderstorms are active south of Panama near the tropical wave. For the forecast, fresh easterly gap winds in the Papagayo region will pulse to strong during the night-time hours through Wed night. Elsewhere, gentle to moderate winds along with moderate seas in southerly swell are expected through most of this week. Scattered heavy showers and isolated thunderstorms near the monsoon trough will linger in the offshore waters of Costa Rica, Panama and Colombia today. ...REMAINDER OF THE AREA... A broad ridge covers the waters north of 20N, anchored by 1033 mb high pressure centered near 40N138W. Fresh to strong NW to N winds and large NW swell cover the waters north of 20N and east of 130W. Fresh to strong NE to E winds and 8-9 ft seas are noted north of 10N west of 125W. Gentle to moderate breezes are noted elsewhere. Seas are 6-8 ft in S swell south of 10N and west of 120W, with 5-7 ft seas in a mix of NW and SW swell elsewhere over the tropical Pacific. Trade wind convergence is supporting scattered showers and thunderstorms are active from 08N to 10N west of 125W. For the forecast, the aforementioned ridge should gradually weaken while retreating northward today. This will allow winds and seas north of the ITCZ to steadily subside from east to west through midweek, becoming gentle to moderate winds with 6-8 ft seas by Thu. Winds south of the ITCZ will also becoming gentle by Thu with higher seas at 5-7 ft in mixed swells.