[pushforbush]

On October 2, 1858, estimated sustained hurricane force winds produced by a tropical cyclone located a short distance offshore were felt in San Diego," said Christopher Landsea, the co-author of a paper on the 1858 hurricane and a hurricane researcher at NOAA's Hurricane Research Division at the Atlantic Oceanographic and Meteorological Laboratory in Miami, Fla. "Extensive damage was done in the city and was described as the severest gale ever felt to that date, nor has it been matched or exceeded in severity since."

Coral evidence suggests the ocean was particularly warm that year and, according to a press release from NOAA, "Warmer waters and a conducive atmosphere allowed the hurricane to sustain Saffir-Simpson Hurricane Scale Category 1 intensity (wind speed of 72-95 mph) as far north as southern California. Available evidence suggests that the hurricane tracked just offshore from San Diego, without the eye coming inland, but close enough to produce damaging winds along the entire coast from San Diego to Long Beach."

Should such a storm return it would cost the region hundreds of millions to billions of dollars in damage according to Christopher Landsea and Michael Chenoweth, authors of the study.

"What this also tells us is that a hurricane has directly affected southern California in recorded history and we should remember that if the conditions are right, the area could get hit again," Landsea said. "Mike and I hope that emergency managers, residents of the area, business owners, the insurance industry, and decision-makers be made aware of this possibility, as most in southern California may think they are completely safe from hurricanes because they are on the Pacific coast instead of the Atlantic."

Impact of Climate Change on Hurricanes

While there is no evidence to suggest that climate change will produce more frequent hurricanes, new research suggests that warmer oceans and seas could produce stronger storms. Late last month an atmospheric scientist at Massachusetts Institute of Technology released a study in Nature that found hurricanes have grown significantly more powerful and destructive over the past three decades. Kerry Emanuel, the author of the study, warns that since hurricanes depend on warm water to form and build, global climate change might increase the effect of hurricanes still further in coming years. It is conceivable that a warmer Pacific could someday enable a hurricane to strike cities farther north, even Los Angeles.

Hurricanes already nearby in Mexico

Hurricanes do batter Baja California (the northernmost state of Mexico, located just south of San Diego) from time to time, usually coinciding with El Niño years. In September 1997, an El Niño year, Hurricane Linda became the strongest storm recorded in the eastern Pacific with winds estimated at 180 mph For a time there was concern that Linda would come ashore in California as a tropical storm, but the storm turned away and the state only experienced high surf and thunderstorms

[MikefromOhio]

Is John a threat to the U.S.?
Eastern Pacific hurricanes are most likely to impact the U.S. in El Nino years, where the ocean along the Mexican coast heats up to much above normal temperatures and can fuel very intense hurricanes. This was the case in 1997, when Category 5 Hurricane Linda, the most intense hurricane ever observed in the Eastern Pacific, moved parallel to the coast and threatened California. The National Hurricane Center issued several advisories for Linda alerting San Diego to the possibility of receiving tropical storm force winds from Linda. The storm turned out to sea before reaching California, however.

This is not an El Nino year, but recent warming of the waters in the Eastern Pacific has led some El Nino experts wondering if a late-arriving El Nino might be on the way. Water temperatures along the Pacific coast of Mexico are 1-2 degrees C above normal all the way to the California coast, giving 2006 the possibility of allowing a tropical storm to reach California. It is very rare for an Eastern Pacific storm to move far enough north to affect the Arizona or California. Since 1900, only four tropical cyclones have brought tropical storm force winds to the Southwestern United States: an unnamed tropical storm that made landfall near Long Beach, CA, in 1939 (52 mph winds south of L.A.); the remnants of Hurricane Joanne in 1972; the remnants of Hurricane Kathleen in 1976 (76 mph wind gust at Yuma, AZ); and the remnants of Hurricane Nora in 1997. In addition, a hurricane just missed making landfall in October 1858 and brought hurricane force winds to San Diego and tropical storm force winds all the way to Los Angeles.

In order to affect California, a tropical cyclone would have to be moving quickly, so the the cold waters off the coast would not weaken it too fast. The alternative would be for the storm to barrel up the narrow Gulf of California, where water temperatures remain warm all the way to the end. To my knowledge, no such storm has ever been able to shoot more than half way up the narrow Gulf of California before dashing itself to pieces on the rugged terrain on either side. I'd be surprised if John manages to bring tropical storm force winds to the U.S.


Dr. Jeff Master's Blog on weatherunderground.com