That region is too far north to be directly affected by the Walker circulation.  Most of the ocean surface off California seems to have warmer than average temperatures (see, for example, here), so I am guessing that the cooler waters reflect local wind conditions and the ocean response.  On the larger scale, the forecast models generally have been favoring warmer than average conditions along the California coast, so I would not rule out a reversal of the cooler conditions you describe.