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Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Wed Sep 17 2025 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 1900 UTC. ...SPECIAL FEATURES... Off the Coast of Southwestern Mexico (EP96): A broad 1007 mb area of low pressure located a few hundred nautical miles off the coast of southwestern Mexico near 15N107W is producing a large area of showers and thunderstorms as described below. Recent satellite derived winds depict that the low is becoming better organized. Environmental conditions appear conducive for further development of this system, and a tropical depression is likely to form in the next day or two while it moves west-northwestward at 10 to 15 kt over the central portion of the east Pacific. Regardless of development, gradually increasing winds and building seas are possible offshore of SW Mexico and SSW of Baja California Sur. There is a high chance for tropical development in the next 48 hours. Please read the latest NHC Tropical Weather Outlook at website - https://www.nhc.noaa.gov/text/MIATWOEP.shtml for more details. ...TROPICAL WAVES... A tropical wave axis is near 86W to the N of 06N to across the Gulf of Papagayo to portions of western Nicaragua, central Honduras and continuing into the NW Caribbean Sea, moving W at 15-20 kt. Nearby convection is discussed in the ITCZ/monsoon trough section below. A tropical wave axis is near 105W/106W, from 04N to 18N near the SW coast of Mexico, moving slowly W at around 5 kt. Nearby convection is discussed in the ITCZ/monsoon trough section below. Please see the Special Features section above for more on the high potential of tropical cyclone formation with this tropical wave and associated low pressure, Invest EP96, along it. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 1010 mb low pressure over northern Colombia near 10N74W to across portions of Panama and Costa Rica to 1007 mb low pressure, Invest EP96, near 15N107W to 1012 mb low pressure near 11.5N132.5W to beyond 10N140W. Scattered to numerous moderate and isolated strong convection is noted from 03N to 10.5N between 77W and 91W, from 05N to 15.5N between 93W and 101W, and from 09N to 18.5N between 103W and 116.5W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the SPECIAL FEATURES section for information on an area being monitored for tropical formation, Invest EP96. Moderate to fresh N to NE gap winds, and seas of 7-8 ft, are funneling across the Gulf of Tehuantepec. The 1009 mb remnant low of Mario is centered near 25N119W. A recent ASCAT scatterometer pass still showed the circulation but that winds have diminished to moderate. Moderate to fresh winds, locally strong, associated with EP96 are off the coast of SW Mexico, where seas are in the 7-9 ft range. An area of fresh N to NE winds is noted off Baja California Norte due somewhat to the flow around and associated with the remnants of Mario. Otherwise, gentle to moderate winds dominate the open waters off Mexico. Light to gentle winds are over the Gulf of California. Seas are in the 4-7 ft range off the Baja California peninsula, and 5-8 ft over the remainder of open waters off Mexico. Seas are in the 1-3 ft range over the Gulf of California, reaching 5 ft at the entrance of the Gulf. For the forecast, fresh to locally strong winds will pulse in the Gulf of Tehuantepec this evening into early Thu, with moderate to locally fresh winds pulsing afterwards through early Sat. Increasing winds and building seas are possible with the area of low pressure, Invest EP96, being monitored with a high chance of tropical cyclone formation. An area of fresh to locally strong winds off Baja California Norte will diminish early Thu. Winds may freshen off Baja California Norte this weekend as the local pressure gradient tightens. Winds will be moderate or weaker elsewhere with moderate to locally rough seas, except slight seas in the Gulf of California. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Winds are mainly light to gentle N of the monsoon trough per recent ASCAT scatterometer data, and gentle to moderate S of the monsoon tough, except moderate to fresh from 01N to 06N. Seas are in the 5-8 ft range in S to SW swell across the discussion waters. Active convection is across much of the offshore waters as described above with locally higher winds and seas possible. For the forecast, rough seas over the regional waters will gradually subside through early Thu. Moderate to locally fresh S to SW winds are expected S of the monsoon trough through early Thu, with moderate or weaker winds elsewhere and otherwise, except locally fresh near the Azuero Peninsula and Gulf of Panama Thu and locally higher near any convection. ...REMAINDER OF THE AREA... Please refer to the SPECIAL FEATURES section for information on an area being monitored for tropical formation, Invest EP96. The 1009 mb remnant low of Mario is centered near 25N119W. A recent ASCAT scatterometer pass still showed the circulation but that winds have diminished to moderate. Outside of conditions associated with the remnants of Mario and EP96, gentle to moderate winds, and seas of 4-7 ft prevail N of the monsoon trough. Moderate to fresh winds prevail S of the monsoon trough. Seas S of the monsoon trough are in the 5-8 ft range W of 120W, and 6-9 ft range E of 120W in S to SW swell. A weak cold front is entering the NW waters near 30N140W with fresh NE winds and building seas in mixed northerly swell behind it. For the forecast, the remnants of Mario will drift WNW and dissipate by Thu evening. Mainly moderate winds will prevail S of the monsoon trough, except locally fresh in the central waters near the axis through the end of the week. Rough seas in the central waters S of the monsoon trough will persist through this evening, then will consolidate around EP96, which has a high chance of tropical cyclone formation. Regardless of development of EP96, expect increasing winds and building seas in its vicinity. A weak cold front will move through the northern waters tonight leading to freshening NE winds and building seas W of the boundary as it slowly stalls and becomes a remnant trough into the upcoming weekend. Marine conditions may improve and be quite tranquil across the open waters by the end of the weekend and into early next week.