First I should mention the significant change of our current weather that Kern County has seen since Thanksgiving. It has been very mild with abundant sunshine in most parts of the state with a notable exception of the central valley. Large high pressure has spent the last few days of November in California helping to bring extremes for its residents- blue skies and highs in the 70s for mountain towns in Kern County, 80s to the coast and LA area with the other extreme of chilly fog in Bakersfield. That high pressure system is about to be chased away. Deep low pressure will be spiraling south into the state from Seattle and the Pacific Northwest. This change is emblematic of what we may see for much of the upcoming winter 2011-12.
Wholesale replacement of a major weather system brings a lot of wind. High Wind WARNINGS are posted for much of the state with northwest to northeast winds expected to gust as high as 80 MPH below canyons and over Sierra peaks. For the south valley our fogginess will be supplanted by a dry and cold air mass. So we will be going from chilly afternoons with low clouds and fog to frigid nights under clear skies. The first killing frost of the season is expected by this Friday and Saturday for central California.
But remember La Nina? It is strengthening after a brief respite this past summer. Sophisticated computer models designed to predict temperature patterns in the ocean are showing a high likelihood that La Nina will persist through the winter. In fact, the models are predicting equatorial Pacific sea surface temperature anomalies of about 1 degree Celsius should cool to about 1.5 degrees in the primary La Nina zone. That is what happened last winter. Does this therefore indicate a repeat of last year's very wet December? Probably not. December 2010 was the wettest month in over 1400 months of records going back to 1889 in Bakersfield. The chance something like that will be repeated is very remote, no matter what is expected in the Pacific. However, people often mistake La Nina with El Nino. I must mention that La Nina is an ocean phenomenon that "usually" causes drier than normal weather for central and southern California. Last December's record rainfall was that much more ironic due to that fact. It is "El Nino" that brings heavy rain to Kern County, not La Nina.
Last winter, I forecast a sandwich season with heavy rainfall at the start and end but dry weather in the middle. It verified nicely. This winter I am expecting a generally cold and dry pattern, more typical of a La Nina cold season. I have also gone on record saying a snow may develop in the south valley, enough to cover the ground. That is NOT to say another January 1999 is in the offing, but something more than the infrequent flurries we have in Bakersfield every few years. With cold weather coming, hopefully there won't be a repeat of the January 2007 hard freeze, either.
So, in summary, December will end up drier than average and colder. This follows a wetter than average October and November 2011. We may see one chilly event with snow levels right down to the valley floor in December or January. The beginning of next year will be cold initially with several hard freeze mornings. A nice January thaw should develop by the end of the month with a few school fog delays. February will be hazy and cool with one or two storms that bring some rain and mountain snow. Moving forward, I think March will fall below expectation on rainfall and end up cooler than normal. Finally, April will have one surprisingly warm period. I dare not get any more specific than that (about the entire winter forecast).
Bring it on! As you must know, the joy in watching weather is its changes and unpredictability.