Note that the strength of relationship between the ENSO condition and rainfall is weaker for individual stations (like Oceanside) than for the rainfall averaged over climate divisions as shown in this blog piece. This is because sampling error (i.e., the noise instead of the signal) becomes a larger issue for individual stations. Oceanside should be affected by the relationship with ENSO in winter. It would require a long record to hope to see it clearly. Using the ENSO condition during winter should make the relationship a bit stronger than using the ENSO condition during previous months predictively (as done in this blog article). But your observations nicely illustrate the looseness of the ENSO-rainfall relationship in winter for an individual station in southern California.