California Gets El Nino Warning

Conditions could generate winter floods, mudslides

Published Wednesday, August 20, 1997, in the San Jose Mercury News

BY FRANK SWEENEYMERCURY NEWS STAFF WRITER

LA JOLLA -- Northern California should expect the worst this winter, bracing for monster storms that could triple the normal rainfall and equal the devastation of the worst El Niño in the last half-century, a team of scientists warned Tuesday.

Fourteen years ago, a succession of Pacific storms smashed the state with widespread death and destruction blamed on the worst El Niño conditions since World War II.

The current threat, scientists said at a workshop at Scripps Institution of Oceanography, is posed by a pool of abnormally warm water stretching halfway across the equatorial Pacific Ocean. But they hedged their warning, acknowledging that there's no hard proof this will happen this winter.

``We can expect warmer coastal temperatures, higher sea levels, more precipitation,'' said Daniel Cayan, director of climate research at Scripps. ``But long-range predictions are very uncertain. This is not a cast-in-concrete event. It could be extreme or mundane -- we're watching to see what end of the spectrum it runs.''

El Niño disrupts weather patterns worldwide. In California, it often means powerful Pacific storms packing high winds and torrential rains, towering surf pounding coastal communities and mudslides rushing down rain-soaked coastal mountain slopes.

Today, the scientists said, we face the same conditions that spawned the wettest winter of the 20th century in Northern California in 1982-83 and triggered natural calamities around the globe.

Scientific workshop

The warning was delivered at a scientific workshop to discuss the coastal impacts of an El Niño winter. Sponsored by Scripps and the California Department of Boating and Waterways, it was attended by more than 280 local, state and federal emergency officials, who may have their hands full when winter storms arrive.

Cayan said this type of El Niño ``predisposes the (weather) system to have more frequent, intense storms coming in succession.'' The signs are there for a phenomenon known as the Pineapple Connection, which brings warm, wet storms from the Hawaiian Islands to California, he said.

Nicholas Graham, of Scripps' International Research Institute for Climate Prediction, called this year's El Niño a ``phenomenal event.'' He said: ``Its (sea surface temperatures) are warmer now than it ever has been this time of year. There is the possibility of some extreme events. Whether they occur remains to be seen, but we should be prepared for them.''

Graham said computer modeling of sea surface temperatures indicates a good chance of triple the normal rainfall this winter. This El Niño, he said, ``is certainly in the class of 1982-1983 and possibly will surpass that event. I've never seen numbers like this in past simulations.''

However, not everyone agreed about this winter's weather. Meteorologist Clive E. Dorman of Scripps' Center for Coastal Studies said there are three kinds of El Niños -- ``a washout, a drought and a wimpout.''

Which one shows up this winter can't be forecast, he said. ``Large-scale models are not God in a box.''

Although the focus was on coastal damage, Chuck Raysbrook, director of the boating and waterways office, pointed out that El Niño causes inland flooding as well and that floods last winter caused $2 billion damage in a non-El Niño year.

The last severe El Niño, which peaked in the winter of 1982-83, spawned a series of storms that caused more than $100 million damage just along the coast. Damage inland also was blamed on the capricious climate change.

In Northern California, communities such as Capitola are particularly vulnerable to the kind of punishment these powerful storms can inflict, although the worst is expected in Southern California.

El Niño is Spanish for ``the Christ child,'' a term initially used by fishermen along the coasts of Ecuador and Peru to describe a warm ocean current that every few years showed up around Christmas and disrupted the fishing season for several months.

Dramatic reversal

Essentially, El Niño is a dramatic reversal of the normal sea temperature, wind and atmospheric pressure conditions in the tropical Pacific, Cayan explained.

The trade winds normally blow from east to west across the tropical Pacific, piling up the warmest water in the world in the western parts of the ocean and pushing the sea level up a foot or two higher than in the east.

The wind-driven western push of water allows cool, nutrient-rich water to rise from the depths off the west coast of South America, nourishing diverse marine ecosystems and major fisheries.

Under these circumstances, a large area of atmospheric low pressure sits over the equator in the western Pacific, where heavy rainfall occurs in the rising, warm air. The eastern Pacific is relatively dry in high pressure centered near Tahiti.

In an El Niño event, the high and low change positions, causing trade winds to weaken and at times reversing course to blow out of the west.

``There is a massive amount of warm water accumulating from the international dateline to the coast of South America,'' Cayan said. ``It is nearly 9 degrees above normal in the core area along the equator, and warm water is creeping north along the coast.''

The rise of cool water from below, that transports nutrients to nourish organisms near the bottom of the food chain, weakens. When the food species decline, the fish that feed on them move elsewhere.

Signs appear

Already, signs of a warm El Niño are showing up in temperate climates. Off the coast of California, species of fish normally found in the warmer waters off Mexico are showing up frequently, said Ronald Dotson of the Southwest Fisheries Science Center.

Scripps oceanographer Reinhard Flick said it would take a combination of events -- very high tides, heavy surf, torrential rains and the higher mean sea level produced by El Niño -- to cause the severe coastal damage seen in 1982-83. And the higher sea level -- already almost a half-foot higher than normal -- ``is the most persistent symptom of El Niño on our coast.''

And Scripps research engineer Richard Seymour said this El Niño has the potential to generate storms sending 20-foot waves smashing onto the West Coast, ``and that means one wave in a thousand is going to be 40 feet high.''

Seymour pointed out that much of Southern California's coastal development occurred in the relatively benign '60s and '70s, ``when we didn't have big waves, and so the '80s were a surprise.''

``The signs are there,'' Seymour warned. ``You need to be prepared.''