The large-scale atmospheric circulation has been pretty consistent with typical La Nina conditions so far, but the heavy precipitation in the northern half of California shows how important the details can be. I will note that the San Francisco Bay area is located between the driest La Nina signal in the Southwest and the wettest La Nina signal in the Pacific Northwest, so the tendency for dry conditions in central and northern California is not that strong, as reflected in the CPC's Winter Outlook. However, the very wet conditions tied to several atmospheric rivers are still atypical for La Nina. We will have to see how everything plays out the rest of this winter. As Mike's Winter Outlook post pointed out, there have been some La Nina winters that were wet in northern California (e.g., 1955-56 and 1995-96), so perhaps this will be another.