A moderate strength La Nina is forecast in 2021. While La Nina climate patterns trend dry for Southern California it isn't always the case. In this video, I show the pattern and the winter forecast for us and the state of California.
Let’s start with a look back at the past five years in Southern California. We had an incredibly strong El Nino the 2015/16 season and hardly got a drop of water. We got a week La Nina 2016/17 and that was a stormy winter season. In fact, it was so rainy in Northern California it erased a six-year drought. A neutral pattern formed 2017/18 and that was dry for us in Southern California.
The last two seasons we've had weak El Nino’s and both of those have been rainy. Last year we received nearly 19 inches of rain, the average is almost 15 inches. We were a tenth of an inch shy this season. The season ended on Sept. 30, 2020. However, Central and Northern California were dry.
This winter a moderate strength La Nina is forecast.
La Nina is simply cooler than average water off the coast of South America. El Nino is warmer than average water temperatures. What both of these climate patterns do is set into motion a series of weather patterns that affect the globe.
For us, in our state, one of two things happens. We can either get a ridge of high pressure that forms over the Pacific and we get dry and warm weather. But our last La Nina the jet stream dipped, and we had a really cool and rainy water year.
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We’ve been tracking La Nina and El Nino since 1950. In that time there have been 22 La Nina’s. Sixteen of those have been below average, Six above. However, when you take a closer look, five of these years, Southern California has been very close to average just slightly below.
So, it's more like nine dry years to 13 rainy ones. There is a trend toward drier than average weather, but it's not a guarantee.
Here is our winter forecast. We think the entire state will get an average amount of precipitation in 2021. That would be great news for Central and Northern California because they were bone dry this past season.
This may also be a warm winter for us. We’re predicting temperatures to be one degree above average. As a reminder, we're a Mediterranean climate, dry in the summer with all of our rain usually falling in a four-month period from December to March.