By Steve Gorman and Dana Feldman
LOS ANGELES (Reuters) - Lightning storms that killed a 20-year-old beachgoer in Los Angeles and sent eight other people to the hospital stemmed from a combination of atmospheric conditions relatively unusual for coastal Southern California, weather experts said on Monday.
A bolt of lightning, accompanied by what witnesses described as an explosive thunder clap, struck near the shore of Venice Beach on Sunday during a storm that materialized quickly and lasted about 15 minutes.
An estimated 20,000 people were at the popular Los Angeles beach when the storm hit, according to Captain Mike McIlroy of the county lifeguard service.
Thirteen people who were in or around the water at the time of the strike were assessed by emergency personnel and eight were transported to hospitals, according to Los Angeles Fire Department spokeswoman Katherine Main.
One of the eight, a man pulled from the water who was later pronounced dead, was identified by the county coroner's office as Nick Fagnano, 20. Another man, reported to be a 57-year-old surfer, was listed in critical condition, and six others were listed in fair condition, one of them a 15-year-old, Main said.
Authorities said a separate lightning strike earlier on Santa Catalina Island, about 22 miles off the Los Angeles coast, injured a man on a golf course.
Lightning strikes are a relatively rare phenomenon along the Southern California shore because cool air from the Pacific tends to chill the thermal dynamics necessary to produce thunderstorms, weather experts say.
But a powerful high-pressure system parked over the Southwest desert over the weekend dragged in warm, moist subtropical air from Mexico with enough energy to form thunder clouds along the beaches, said John Dumas, a meteorologist for the National Weather Service office in Oxnard, California.
Bill Patzert, a climatologist with NASA's Jet Propulsion Laboratory, said lightning strikes in coastal Southern California are rare, with a probability estimated at 1-in-10 million.
By comparison, the odds of lightning strikes are 10 times higher in Florida, which ranks as the U.S. capital of thunderstorms and lightning, he said.
Just 23 U.S. lightning deaths were documented last year, well below the annual average of 73 recorded during the past few decades, Patzert said, citing National Weather Service data. On a much grander scale, lightning strikes the surface of the Earth 8.6 million times a day, he said.
(Writing by Steve Gorman; Editing by Jim Loney)