November Classic

If you think all the hot, dry weather we’ve had the last couple of days means that you can forget about those forecasts of heavy El Nino rains this winter, you’re probably over-optimistic.

Meteorologists say the two weather phenomena have little to do with each other.

The summer-like conditions of late have been the result of a classic November Santa Ana condition, caused by a large, stationary ridge of high pressure parked over the Desert Southwest.

Winds circulating around this ridge have been drying out and heating by compression as they sweep down mountain canyons and into the coastal communities of Southern California. These same winds have been keeping the normal cooling breezes from the Pacific at bay.

The result: A record high reading of 99 degrees at the Los Angeles Civic Center on Sunday, followed by a high of 94 on Monday, two degrees below the record for the date. Relative humidity dipped both days to a throat-parching 11%. It should be nearly as hot and dry again today, meteorologists say.

But they are quick to add that they still expect drenching rains, beginning next month, that could match the devastating downpours during the El Nino winter of 1982-83.

In 1982-83, 31.3 inches of rain fell on the Los Angeles Civic Center, more than twice as much as normal. At least 14 deaths in California were blamed on that winter’s hammering surf, widespread flooding and destructive mudslides. Statewide damage was estimated at $265 million.

When scientists compare ocean-temperature statistics and other oceanographic data from the 1982-83 El Nino with the current one, “they look a lot alike,” said Tim Barnett, a geophysicist a the Scripps Institution of Oceanography in La Jolla.

“The biggest difference is that this year’s started three to four months before most previous El Ninos,” he said. “We’re not sure what that means, but so far, it’s doing everything that we expect an El Nino to do.”

Barnett said this year’s El Nino has the trademark characteristic of all the rest--a shift in the low-level equatorial trade winds. The wind shift has caused a massive tide of warm subsurface water to migrate eastward across the Pacific to the west coast of South America before welling up and washing back westward along the ocean’s surface.

Because winds that normally accelerate the westward flow of surface water have shifted and weakened, this movement is sluggish.

The result is a pool of warm surface water--overlain by a vast center of moisture-laden air--near the international date line, Barnett said. Within a month, he said, “flares” of warm, moist air from this center will begin sweeping east toward Southern California, carried along by the southern arm of high-altitude jet stream winds.

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When this moisture hits Southern California’s coastal mountains, it will start falling as rain, meteorologists say. And they say that when this warm, most air collides with the cold air that pours south sporadically from the Gulf of Alaska during the winter, the rain will be unusually heavy.

“We could see as many as five two- to three-day periods during which two inches of rain or more will fall each day,” Barnett said.

All of that is probably at least a month away, he said. El Nino rains usually don’t start in Southern California until December, he said, and the condition this year is expected to last through March.

For the next few days, at least, the forecast looks pretty good.

John Sherwin, a meteorologist with WeatherData Inc., said that although a high temperature of about 90 is expected in downtown Los Angeles today, the heat wave will soon come to an end.

“The high pressure ridge is starting to weaken and the sea breezes are starting up again,” he said. “By Wednesday, the downtown high will be about 82, and fog will begin to develop along the coast.”

The cooling trend is expected to continue through the weekend.