- NHC Eastern Pacific Tropical Weather Discussion
by nhcwebmaster@noaa.gov (nhcwebmaster) on October 15, 2025 at 4:04 AM000AXPZ20 KNHC 150404TWDEP Tropical Weather DiscussionNWS National Hurricane Center Miami FL0405 UTC Wed Oct 15 2025Tropical Weather Discussion for the eastern Pacific Ocean from03.4S to 30N, east of 120W including the Gulf of California, andfrom the Equator to 30N, between 120W and 140W. The followinginformation is based on satellite imagery, weather observations,radar, and meteorological analysis.Based on 0000 UTC surface analysis and satellite imagery through0345 UTC....INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...The monsoon trough axis extends from northern Colombia to along the coast of central Panama and west-northwestward toacross northern Costa Rica, and continues northwestward tolow pressure, Invest EP91, near 12N94W 1008 mb to 09N105W to 11N114W and to 08N124W, where it transitions to the ITCZ to09.5N135W to 10N140W. Scattered moderate convection is seenfrom 06N to 10N between 94W and 102W....OFFSHORE WATERS WITHIN 250 NM OF MEXICO...A trough extends from SW Arizona southwestward to across the northern Gulf of California while broad high pressure is westof the Baja California peninsula ahead of a cold front that extends from near 30N119W to 28N126W to near 30N135W. A tight gradient associated to the trough was producing fresh to strong SW winds over the northern Gulf waters as seen in the latest scatterometer satellite data pass. Fresh to near gale-force northerly gap winds are ongoing in the Gulf of Tehuantepec with 1008 mb low pressure, Invest EP91, located to the southeast of the Gulf region along the monsoon trough near 12N94W. Seas over this area 5 to 7 ft. Winds are moderate or lighter under the broad high pressure as noted in the latest scatterometersatellite data passes. Locally fresh northwest winds are near Cabo Corrientes and Cabo San Lucas. Seas are 5 to 7 ft W of 110Wand offshore Baja California in northwest long-period swell, except building to around 7 ft just ahead of the front, and 4 to6 ft elsewhere E of 110W in primarily south to southwest swell. In the Gulf of California, seas are 4 to 6 ft in the northern portion, and 2 to 4 ft elsewhere.For the forecast, moderate to fresh winds in the northern Gulf of California will linger into Wed as a cold front approaches with troughing ahead of it. Northerly swell will spread through the waters west of Baja California tonight into Wed in the wake of a weakening cold front that will move across Baja California and the Gulf of California. Winds will freshen behind the front offshore Baja California through Thu night as high pressure builds in locally strong from near Cabo San Lazaro northward Wed night into early Thu. Winds then will weaken there by the end of the week into the weekend as the gradient slackens. Fresh to strong northerly gap winds will persist in the Gulf of Tehuantepec through early Thu afternoon. Meanwhile, a broad area of low pressure, Invest EP91, is near the coast of southern Mexico. Environmental conditions appear conducive for gradual development, and a tropical depression could form late this week or over the weekend. This system is expected to move little during the next few days, but a slow northwestward motion near the coast of southern and southwestern Mexico is expected by the weekend. Regardless of development, expect increasing winds and building seas. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR...A broad 1008 mb low pressure, Invest EP91, located near the coast of southern Mexico and portions of Central America, is producing a large area of disorganized showers and thunderstormsas described with the monsoon trough/ITCZ section above. Associatedwinds are moderate to fresh offshore Guatemala and far western El Salvador. Winds are moderate or lighter elsewhere. Seas are4 to 6 ft in primarily southwest swell over these waters.For the forecast, environmental conditions appear conducive for gradual development, and a tropical depression could form late this week or over the weekend. This system is expected to move little during the next few days, but a slow northwestward motion near the coast of southern and southwestern Mexico is expected bythe weekend. Regardless of development, expect increasing winds and building seas, mainly west of the offshore waters of Guatemala. Winds may freshen south of the monsoon trough as it lifts northward through the remainder of the week, which would build seas slightly. ...REMAINDER OF THE AREA...A rather fast moving cold front extends from near 28N121W to 28N126W and northwestward to near 30N135W. Latest scatterometer satellite data passes reveal gentle to moderate northwest tonorth winds behind the front. A 0230Z Jason-3 altimetersatellite data pass reveals seas of 8 to 11 ft in long-period north swell behind the front. Otherwise, a broad ridge is acrossthe waters north of the monsoon trough and ITCZ ahead of the front. The gradient between the ridge and relatively lower pressures in the ITCZ/Monsoon Trough region is allowing for gentle to moderate winds north 09N and west of about 116W.Seas are mainly 4 to 7 ft away from the northerly swell in a wide variety of mixed swell.For the forecast, the cold front will move southeastward acrossthe waters N of 20N through Thu while weakening and eventually dissipating. Winds will locally freshen behind the front as highpressure builds in across the area. The seas of 8 to 11 ft in the long-period north swell will continue to press southward throughThu while decaying. Farther south, weak low pressure is likely to form along the monsoon trough between 115W and 1202 through Thu night. Looking ahead, a reinforcing set of long-period northwest swell may arrive by the end of the week into the weekend over the northwest and west-central portions of the areamaintaining seas to a rough state, with yet another set possiblyarriving early next week.$$Aguirre