October 18, 2012
Hurricanes And Tropical Cyclones Not Likely To Hit Southern California
Lee Rannals for redOrbit.com - Your Universe Online
California has felt the effects of a tropical cyclone before, but typically just in the form of rainfall from the remnants of a storm in the eastern Pacific.
There has actually never been a documented case of a hurricane making landfall in California, but it has had some close calls in the past century.
The state has faced some gale-force winds by an unnamed California tropical storm in 1939, Kathleen in 1976 and Nora in 1997. However, the primary threat for Californians during these storms is the rainfall, rather than the winds.
Jet Propulsion Laboratory oceanographer and climatologist Bill Patzert said that statistically speaking, having a hurricane make landfall in California is a 1 in 1,000 chance.
He said for those seasons when California does get infected by a tropical storm system, it has happened in September.
"There are two main factors that work against hurricanes here: cool waters off the coast and the direction of the upper-level winds," Patzert said in a prepared statement.
He said tropical cyclones draw their fuel from heat stored in the upper ocean. Ocean surface water greater than 80 degrees Fahrenheit are required to form and fuel these storms.
"During the Northern Hemisphere summer and fall, the upper layers of the tropical oceans (down to approximately 330 feet depth) are steadily heated. By September, when hurricane season hits its peak, these waters reach their maximum temperatures, becoming, in a sense, high-octane fuel for hurricanes," he added.
He said while water temperatures never get that high, on rare occasions they may reach about 75 degrees Fahrenheit near the shore of Southern California.
The cool-water California Current acts as a hurricane repellant, according to Patzert, protecting the state and Northern Baja California from hurricanes.
"The other factor at play here is the upper-level winds, which tend to carry and steer storms to the west and northwest, away from California, and also tend to shear the tops off of hurricanes, breaking them apart," he said.
He said between upper and lower-level winds, there is a lot of wind shear off the coast in Southern California.
"These prevailing northwesterly winds also push warmer surface waters offshore, drawing cooler waters up to the surface, and this further adds to the cool nature of the nearby ocean waters that would weaken any storms that did approach California," Patzert said.
For a "Perfect Storm" to take place and hit Southern California, it would have to take place during a "Godzilla" El Nino event, he said.
For this season, Patzert said the temperatures off the Southern California coast are going to be way too cold for hurricanes. When speaking of the future, and the climate's impact on those coastal water temperatures, he said that no one is sure on how it could affect hurricanes gaining power on the Golden State.
"Nobody knows yet, and if anybody tells you they know the answer to that question, kick 'em out of your Rolodex file," he said. "In fact it's possible that there might be fewer hurricanes in a warming world. But the bottom line for Southern Californians is that even if global temperatures were to rise six degrees, a hurricane in California would rank very low on the list of things we'd need to worry about."