Based on results from a ROMS numerical model, the dynamics of the Mexican Central Pacific was studied during three years (2003–2005). The model reproduces the mean and seasonal variability of sea surface temperature, as well as mesoscale eddies and meanders from satellite observations. The model adequately represents the main currents in the region: California Current, Mexican Coastal Current, and Gulf of California currents. The Gulf of California currents are linked to the intensificiation of the Mexican Coastal Current and interact in such a way that the lateral shear generates eddies at the entrance to the Gulf of California. The mesoscale eddies were found to have a depth of ~200 m. The eddies generated in the area (internal Rossby radius of deformation, Rd = 40 km) had a diameter L of ~300 km, an orbital speed of 20–30 cm s–1, and a westward translation speed of ~4 cm s–1. Eddies are considered from intermediate to big (L≈  7.5 Rd, Ro << 1), show geostrophic dynamics, and present a westward drift due to Coriolis variation with latitude (beta effect). The size of the eddies seems to be related to the weakening of the meridional component of wind stress during the North American monsoon.

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We used a high‐resolution numerical model implementation to analyze the California Undercurrent (CU) dynamics along the Southern California Current System. In agreement with reported observations, the modeled CU was stronger during June–July and December–January, when it flowed continuously along Baja California and Southern California reaching long‐term averages up to 6 cm s−1. Previous research has associated the biannual CU intensification to the local dynamics off Southern California. Our results evidenced, however, that the passage of remote Semiannual Coastal‐Trapped Waves (SCTW) primarily explained the semiannual CU variability. The CU was stronger 2–3 months after the passage of the upwelling SCTW phase, when the offshore propagation of Rossby waves, brought about by the SCTW transit, induced an energetic cross‐shore pressure gradient that strengthened the subsurface poleward circulation along the continental slope. The SCTW were independent of the local wind; they corresponded to the northward extension of semiannual equatorial Kelvin waves that have been observed along the northeastern tropical Pacific.

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