When zonal velocity profiles from the central equatorial Pacific are expanded into sums of vertical normal modes, the peak amplitudes occur consistently near modes 1, 5, 12, and 18. The first two of these peaks sum to a recognizable equatorial undercurrent profile. The two higher-mode peaks blunt and thicken the equatorial undercurrent (EUC) and add a westward extremum near 340 m. During the 1982--1983 El Ni¿o, the low-mode component of the flow (modes 1--10) was more variable than the residual component, which was dominated by the modes near 12 and 18. The residuals below 120 m persisted as alternating westward and eastward current bands (the ''shallow jets'') through the disappearance of the EUC in the second half of 1982 and its reappearance in 1983. The shallow jets were nearly constant in depth until late 1982 and then gradually rose through the end of the time series in June 1983. Differences in temporal behavior among the mode amplitude peaks indicate that these peaks are describing dynamically separate components of the flow which are not tightly coupled on time scales shorter than a few months. ¿ American Geophysical Union 1988