Last updated May 23, 2018

Ridiculously Resilient Ridge

Climate change may be at least partly responsible for the unprecedented high-pressure weather pattern (known as the “ridiculously resilient ridge”) that has blocked storms from the state of California, leading to an increase in hot and dry weather.

RRR observations

In 2013, a high-pressure zone formed over the Pacific Ocean, diverting precipitation towards Alaska. While these zones are common, they normally change position quickly. The recurring high-pressure “ridge” is unprecedented in modern weather records in that it remained in place for many months at a time, held by a large, static bend in the jet stream.

RRR trends and projections

An April 2016 study investigating changes during California's October to May "rainy season” identifies a significant increase in the occurrence of atmospheric patterns associated with certain precipitation and temperature extremes over the 67-year period.[1] The study identifies in particular that  both thermal expansion and sea level pressure trends contribute to a notable increase in anomalous northeastern Pacific ridging patterns similar to that observed during the 2012–2015 California drought.[1]