In particular, during El Nino years, when the tropical Pacific is warmer than normal, we often experience low pressure off the West Coast, with storms shunted into California.
You can see the anomalous low pressure to our southwest.
Why does El Nino set up this pattern? Why do warm sea surface temperatures in the tropical Pacific associated with El Nino alter the pressure and wind patterns off the West Coast.
First, the warm waters of El Nino perturb the atmosphere above.
A series of waves....called Rossby Waves...then propagate into the midlatitudes, causing a series of low and high-pressure pressure areas.
The jet stream....the current of strong winds in the upper troposphere... is distorted by this wave pattern.
In the atmospheric case, big thunderstorms above the warm water act as the "Rock," During the next few months as El Nino makes way for La Nina, the central Pacific water will cool, the thunderstorms will shift westward, and the wave pattern change substantially.
https://cliffmass.blogspot.com/2024/02/why-does-el-nino-influence-west-coast.html
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