The propensity for an anticylonic eddy (~100- to 200-km diameter) to develop west of Point Arena during the summer is documented with an analysis of satellite derived sea surface temperature (SST) data and a review of published historical hydrographic data. The satellite data span the period from 1981 through 1989 and the hydrographic data include CalCOFI surveys from 1949--1959 and a few more recent studies. A closed anticyclone was apparent in many of the historical dynamic height maps, while a meander pattern, lacking closed contours, characterized the coincident hydrographic 10-m temperature maps. A conceptual model of an eddylike perturbation imbedded in a broader equatorward flow is adopted as a working hypothesis. In this simplistic model, the only distinction between an eddy like perturbation. This led to a method to detect the eddies in the satellite SST data, which were dominated by meanderlike patterns: A linear trend was subtracted from each image to remove large-scale SST gradients, leaving an expression of the residual eddylike perturbation. Composite images over select time periods were produced for analysis by computing spatial variance EOFs of the detrended data. With this approach, a warm-core eddy was evident at Point Arena in summertime satellite SST data from 1981--1985 and 1987--1989 (formation of an eddy in 1986 remains unresolved because the readily available SST data were incomplete).

The eddy was bounded on the inshore side by the jet and filament system studied during the 1987 and 1988 Coastal Transition Zone (CTZ) program. Recurrence of this eddy was apparently coupled with the recurring cold filament commonly observed at Point Arena during the summer. The coevolution of the eddy and meandering jet during 1988 was studied with sequential composite empirical orthogonal function (EOF) satellite SST images. These shows that a deep anticyclonic meander was present near Cape Mendocino and directed the jet toward shore. In the late July 1988 this meander pinched off a new eddy, and the subsequent jet flow was redicted southward and displaced farther offshore. These events account for the transition in the jet observed in the July CTZ hydrographic surveys. The length scale and position of the Point Arena eddy is consistent with a standing wave, phase locked to a prominent cape (in this case, Mendocino). The significance of the apparent splitting off of an eddy in 1988, as well as the apparent preponderance of anticyclones evident in these EOFs, is discussed relative to recent theoretical and numerical model developments.