Last updated: January 10, 2022
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Climate Corner: What do Heavy Autumn Rains Mean for California’s Drought Status?
Weather West Blog / tropicaltidbits.com
November 2021 - It’s been confusing to see highway signs asking Californians to conserve water due to the severe drought, given October’s intense rainfall. Unlike the previous several years, fall 2021 in California was not characterized by wildfire smoke. Instead, northern parts of the state witnessed record-breaking rains, most of which occurred during a single two-day October storm. Thanks to that single atmospheric river event, October 2021 was the wettest on record since 1895 for 10 counties across Northern California. It was the fourth wettest for the entire state. And because the landscape was so parched before October, dry soil and low rivers absorbed much of the downpour, mitigating what could have been severe flood damage.
But what does that mean for California’s drought status? Though the rainfall offered some much needed and well-timed relief for parts of northern California plagued by drought for several years, it’s probably not a sign of broader drought relief. As of November 2021, the region remains in severe to exceptional drought–a designation only slightly reduced by all that October rain.
Seasonal predictions are still pointing towards a drier-than average winter and spring
The combination of weather patterns right now, including La Niña, will likely push storm systems north of California. This spells a dry start to the winter season.
In September, NOAA’s Climate Prediction Center announced that a La Niña had developed in the Pacific and was likely to last through the winter. La Niña is part of the El Niño Southern Oscillation (ENSO) – a dramatic, cyclical variation in the Earth’s climate. Warm El Niño and cool La Niña episodes happen every few years in the tropical Pacific Ocean, affecting global agricultural and economic systems.
La Niña increases chances for dry conditions in the southern the U.S and wetter conditions for Indonesia, Australia and parts of the Amazon, while El Nino does the reverse. So as La Niña continues, we can expect a drier winter and spring, particularly for southern regions of California.
How might these cyclical weather patterns be changing as the climate changes?
It’s complicated, as no two El Niños or La Niñas are perfectly alike. But NOAA scientists have just published a new book that explores some of this complexity, and some predictions are clear: under business as usual greenhouse gas emission scenarios, we may see an increase in the frequency and strength of extreme El Niño and La Niña events as well as shifts in the latitude of these dramatic storms. Some ENSO impacts are already being amplified, including coral bleaching and increases in tropical storm activity.