REPORTS OF TORNADOES INCREASE, EVEN IN CALIFORNIA.

Byline: Associated Press 

Californians bracing for earthquakes should consider preparing for times when they'll have to batten down the hatches.

The number of tornadoes reported in California has more than doubled in the past 10 years, according to the National Centers for Environmental Prediction.

An average of 13 tornadoes a year were reported from 1990 to 1994, while an average of six a year were reported in the 1980s, according to the Kansas City-based National Centers for Environmental Prediction.

California weather forecasters for decades wouldn't take tornado reports seriously, says Jack Hales of the National Centers, a branch of the U.S. Commerce Department that issues severe storm warnings.

"There's a mind-set of people in the West that tornadoes are something that occur in the Plains," says Hales, who has researched the frequency of California twisters.

However, the actual number of tornadoes may not be increasing. It could be that there are simply more people around to see and record them - the result of population growth and growing scientific interest.

"I saw a tornado blow a tractor maybe 50, 60 feet in the air at Chowchilla in 1991," says Steve Johnson of Fresno, who helped organize the Association of Central California Weather Observers. The 5-year-old group claims almost 200 members.

The world's strongest tornadoes occur in the Midwest, where they feed off abundant warm, moist air flowing inland from the Gulf of Mexico.

California tends to lack a steady source of hot and humid air, so its tornadoes tend to be weaker, smaller and shorter-lived. Most California tornadoes have winds of less than 100 mph, compared with vicious Midwest storms with winds exceed 200 mph.

Nationwide, the number of tornado reports has skyrocketed since the early 1950s - from 200 in 1950 to more than 1,000 a year in the early 1990s.

Decades ago, most Central Valley tornadoes were obscured by clouds and rain in remote corners of farmlands. They damaged little more than anthills or irrigation networks.

But with increasing valley development, experts say it's just a matter of time before someone in California is killed by a twister.

"We've been remarkably fortunate (in California) and there's no reason to presume that good fortune will continue indefinitely," Warren Blier, an assistant professor of atmospheric science at the University of California, Los Angeles, told the San Francisco Examiner.

"I would suspect that at some point somebody is going be killed by a tornado in California, especially in the greater Los Angeles and Orange County areas because of the high urban density," Blier said.

Findings on the cause of tornadoes will be discussed starting Monday at the American Meteorological Society's Conference on Severe Local Storms at the Cathedral Hill Hotel in San Francisco.