The Weather Phenomenon That Recently Hit California
When the rain began to fall in California and did not stop, residents took to social media with glee. Rain boots that had not seen moisture in months surfaced from the backs of closets as there was a near-audible collective sigh of relief for Californians.
Many were thinking that the deluge would tame the wildfires and stifle drought conditions across the state. When flash flooding warnings surfaced, high winds kicked up, mudslides were triggered, trees toppled and power went out, many residents still felt their spirits buoyed by the continual rain – a calming gift after months of extreme temperatures and constant threat of expanding–and new–wildfires.
“The storm follows the busiest wildfire season in California history and heightens threats of flash flooding. Much of the region is in severe, extreme or exceptional drought, as classified by the U.S. Drought Monitor,” according to Reuters.
Still, burn areas were hit particularly hard, as often happens when the mud has nothing to hold it in place and the saturated earth can move with devastating force.
A lot of people were filled with such relief from the gift of rain that they did not think or care about what forces of nature collided and clouded the skies to make rain fall like it did. But after an extended and devastating drought, some meteorologists sought to educate the public on what exactly was at play.
The storm system convergence consisted of a “bomb cyclone” and an “atmospheric river” and was so massive that it reached into British Columbia the same day it hit California.
A bombogenesis is a rapid intensification of a mid-latitude cyclone in which the pressure drops “at least 24 millibars over a 24-hour period.” The lower the atmospheric pressure, the stronger the storm. That rapid storm intensification causes a bomb cyclone. The recent bomb cyclone to hit California merged with an atmospheric river, or as the National Oceanic and Atmospheric Administration explains it “relatively long, narrow regions in the atmosphere – like rivers in the sky– that transport most of the water vapor outside of the tropics.”
When the bomb cyclone merged with an atmospheric river, it created a “giant train of moist air in the atmosphere.”
Although so many were welcoming the rain to offset wildland fire risk, burn scar areas that had previously been met with wildfire were at heightened risk of dangerous flash flooding. Multiple mudslides were reported in areas of the Sierra Nevadas that were plagued by the second largest fire in state history, according to Reuters reporting.