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Move Over Atmospheric River and Make Way for the Fujiwhara Effect



A sign on Highway 41 in central Fresno warns of severe weather including high winds and rain on Tuesday, March 21, 2023. (GV Wire/Jahz Tello)
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The term “atmospheric river” has become old hat for Californians, who’ve experienced 12 of them through winter and the start of spring.

However, other perhaps unfamiliar meteorological descriptions are being introduced to Golden State residents amid the unrelenting rain and snow.

Tuesday produced what is known as the “Fujiwhara effect” in the Bay Area. That occurred when a system developed two “eyes” of low pressure producing a double-barrel blow to San Francisco and Santa Cruz.

Here is a description of the Fujiwhara effect courtesy of the National Weather Service:

“When two hurricanes spinning in the same direction pass close enough to each other, they begin an intense dance around their common center. If one hurricane is a lot stronger than the other, the smaller one will orbit it and eventually come crashing into its vortex to be absorbed. Two storms closer in strength can gravitate towards each other until they reach a common point and merge, or merely spin each other around for a while before shooting off on their own paths. In rare occasions, the effect is additive when the hurricanes come together, resulting in one larger storm instead of two smaller ones.”

Tuesday’s storm blasted the Bay Area with powerful gusts and downpours, pounded Sacramento with intense hail, and triggered a rare tornado warning on the Southern California coast.

The damaging winds, rain, and snow, were blamed for two deaths and forecasters said additional flooding will continue in parts of the state, including the San Joaquin Valley.

Some 121,000 customers were without electricity early Wednesday throughout the state, according to

People watch large waves along The Embarcadero near Pier 14 between Mission Street and Howard Street in San Francisco on Tuesday, March 21, 2023. (Salgu Wissmath/San Francisco Chronicle via AP)

The Valley Forecast

A Winter Storm Warning will remain in effect through 11 p.m. Wednesday, the National Weather Service in Hanford said.

The Valley forecast calls for scattered showers continuing overnight, especially in the Sierra Nevada and foothills.

NWS says that the rain should clear out of the Valley on Thursday but to expect cooler-than-normal temperatures and mountain showers through the weekend.

Another low-pressure system could bring the return of rain by next Tuesday.

Tulare County Deals With Flooding

More than 60 sheriff’s deputies and police officers from Tulare County and neighboring agencies are helping residents deal with flooding and evacuations.

The Tulare County Sheriff’s Office said in a Facebook post that personnel are focused on keeping residents in Allensworth and Alpaugh, in particular, out of harm’s way.

Although several roads throughout the county have sinkholes, mudslides, washouts, and flooding, the areas along Highway 43 are the worst, the sheriff’s office said. Making the situation even more dangerous: People are ignoring road closures and becoming stranded.

Flooding in Tulare County (Tulare County SO)

Mammoth Mountain Ski Resort Will Be Open Through July

The Mammoth Mountain resort in the eastern Sierra Nevada announced that it will remain open for skiing and snowboarding at least through the end of July.

With a season-to-date snowfall of 634 inches at the main lodge, it was likely just one storm away from breaking the all-time record of 668 inches set in the 2010-2011 season.

(Associated Press contributed to this article.)

Bill McEwen is news director and columnist for GV Wire. He joined GV Wire in August 2017 after 37 years at The Fresno Bee. With The Bee, he served as Opinion Editor, City Hall reporter, Metro columnist, sports columnist and sports editor through the years. His work has been frequently honored by the California Newspapers Publishers Association, including authoring first-place editorials in 2015 and 2016. Bill and his wife, Karen, are proud parents of two adult sons, and they have two grandsons. You can contact Bill at 559-492-4031 or at Send an Email