What a mighty, drenching cyclone.
An unusually strong mid-latitude cyclone — a sprawling, comma-shaped storm occurring in the middle latitudes — deluged much of the parched West Coast with extreme rains over the weekend. Some rainfall, like in Sacramento, broke records.
These cyclones are comprised of air and clouds rotating around an area of low atmospheric pressure, and a prodigious amount of moisture (water vapor) wrapped around this late October storm. This potent band of moisture, a part of the storm aptly dubbed an “atmospheric river,” dumped immense rains. Water poured through the drought-stricken Sierra Nevada, triggered major landslides, and also dropped some much-needed snow.
The satellite images below, taken by National Oceanic and Atmospheric Administration satellites, show vivid images of the potent, counter-clockwise spinning cyclone, which traveled farther inland on Monday.
Atmospheric rivers are crucial weather events in California. They deliver about half the Golden State’s water supply, but their occurrences fluctuate significantly from year to year, resulting in periods of intense drought or immensely wet seasons.
Yet in an incessantly warming world, extremes are becoming more extreme. Droughts are becoming hotter and drier, and powerful storms are dumping more intense, destructive rains. A warmer atmosphere holds more water (for every 1.8 degrees Fahrenheit of warming, or one degree Celsius, the air holds about seven percent more water vapor), which boosts the odds of strong storms dumping significantly more precipitation.
“You’re raising the ceiling on precipitation potential,” Daniel Swain, a climate scientist at the National Center for Atmospheric Research, told Mashable in 2019. “Atmospheric rivers will be more intense, delivering more water.”
Atmospheric scientists expect California’s water cycle to grow increasingly extreme and volatile as the planet warms. The latest storm, occurring amid a historic drought, is a vivid example.
“It is worth noting that this exact situation — an extremely strong atmospheric river bringing [a] brief period of record rainfall in midst of [a] severe and temperature-amplified drought — is what we expect to see in California with #ClimateChange,” Swain tweeted on Sunday.
