Parts of the San Francisco Bay Area have now moved out of “severe drought” conditions after this week’s bomb cyclone.
In 2022, a study published in the journal Nature Climate Change found California’s last comparable, multidecadal drought— though not as severe — occurred in the 1500s. Last year saw Lake Orville, the state’s second-largest water reservoir, went down to historic lows; at its driest, the reservoir, which is capable of storing 3.5 million-acre-feet of water, reached just 28% capacity.
This week’s bomb cyclones that drenched Northern California offered a stark paradox to 2022’s parched conditions. Now, according to the U.S. Drought Monitor (USDM), California is now free of “extreme drought” conditions — a first in years.
Week over week drought classification/improvement. Area in D4 (Exceptional Drought) is no longer on the map. The drought monitor class change map also helps show where there was 1 class (category) improvement. #CAwx pic.twitter.com/NlltVDBlwc
— NWS Bay Area 🌉 (@NWSBayArea) January 6, 2023
“Week over week drought classification/improvement,” reads a tweet from the San Francisco Bay Area chapter of the National Weather Service. “The area in D4 (Exceptional Drought) is no longer on the map. The drought monitor class change map also helps show where there was 1 class (category) improvement.”
A closer look shows much of the South Bay and Peninsula areas have moved from “moderate drought” conditions, away from “severe drought” levels. While “extreme drought” conditions still run vertically up and down the Sierra Nevada mountain range, they’ve shrunk horizontally.
To gauge the level of drought, the U.S. Drought Monitor map uses a combination of variables, which include measuring soil and streamflow, across various timelines, and transcribing those figures onto state, regional, and national maps. The current map for California shows the entire state is experiencing drought conditions; only parts of Southern California and a corner of the Oregon-California border are experiencing “abnormally dry conditions” — the least severe level of drought given by the USDM.
Another spat of rain is expected to wet the region over the next seven or ten days. Though the looming rainstorms won’t produce sudden levels, the weekly rain total could fall in the 4” to 5” range between January 7th and January 13th… causing even more flooding. Potentially worse in some areas; the ground in many places is completely saturated and incapable of holding any more moisture; the risk of mudslides, sinkholes, and flash floods is expected to be elevated over the next week or so.
As the climate crisis worsens, these unusually strong environmental extremes will become increasingly more common. While we should all revel in the fact reservoirs are refilling across the state, we must also take note of the pendulous nature of these weather patterns.
Feature image: Screenshot via U.S. Drought Monitor
