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When tornados touch down – in California?

March 2, 2011

Category: News & Notes

With sights on supercell thunderstorms,

SFSU’s Monteverdi tracks twisters

Supercell storm near Limon, Colo., 2005 (photo by J. Monteverdi)

By Sean Kearns, CSU Public Affairs

John Monteverdi enjoys his whirlwind schedule.John Monteverdi, SFSU meteorology professor

Every year, as soon as spring term ends at San Francisco State, he packs up and heads out on his annual tornado safari – which has taken him throughout Texas, New Mexico, Kansas, Oklahoma and beyond in search of supercell thunderstorms.

(About 10 percent of supercells will trigger the sequence of cascading events that spawns a tornado.)

Sometimes, Monteverdi heads out in a major hurry, trying to catch up to a sudden supercell sighting in California.

Wait a minute. Tornados in California?

“Yes,” said Monteverdi. “They’re not the monster tornados of the Great Plains, but they are significant.”

In two key California regions – in the Southland stretch of Ventura, Los Angeles and Orange counties and in the eastern Central Valley, from Bakersfield north to Chico – the frequency of tornados approaches that of Oklahoma, he said. In 2004, possibly the highest-elevation tornado recorded was seen in Sequoia National Park, as shown on San Francisco State’s geosciences website.

“I’m surprised that nobody’s been killed in California,” Monteverdi said. He cites two factors that have helped spare lives: 1) many of the areas where tornados frequent are sparsely populated, and 2) luck.

(Monteverdi also contributed to “A Closer Look” at La Niña weather in California in Science & the CSU.)

How tornados form - NOAA diagramIn March 1983, a tornado ripped through Los Angeles, ripping much of the roof off of the Los Angeles Convention Center (about 10 miles west of Cal State L.A.). According to Monteverdi, U.S. weather officials were long disinclined to acknowledge tornados in the Golden State, so at the time they called it “wind damage.”

Now one of Monteverdi’s students is reconstructing the event’s data to get a clearer sense of what happened; and one of his colleagues at the National Weather Service believes it may have been an F-3 or F-4 tornado, from “severe” to “devastating” on the Fujita scale.

Also in 1983, a few blocks from the San Francisco State, Monteverdi watched a thunderstorm create a waterspout over Lake Merced. Moments later came reports of damage on campus and, later, at the Hayward Airport across the bay.

His student is also examining records of a 1951 tornado in Sunnyvale that, while laying trees down in a counter-clockwise pattern, also destroyed a subdivision and moved a large construction crane a city block. Another tornado hit Sunnyvale in 1998.

“Tornado-chasing is incredibly exciting, addictive, an adrenaline rush,” he said. “It can also be very boring.”  And sometimes frustrating: “By the time I get there, it’s usually gone.” Like the time he took off after reports of funnel clouds in the Central Valley: “I got to Fresno and the tornado hit Visalia.”

He says he always has been and always will be “drawn to the weather.” Unlike a moth to a flame, he only goes so far. “We do not drive into tornados.”

John Monteverdi is silhouetted with tornado in distance in Miami, Texas, in 1994.

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