Another Perfect Year in Paradise

The meteorological season, measured for some arcane reason from July 1 to June 30, has come to a close and scientists studying Los Angeles weather patterns have boiled down reams of data to two conclusions: The last year was warm and, for the most part, it was dry.

Tell me something I don’t know, right?

According to the data, the elements in Southern California behaved quite obediently in the 1999-2000 weather season, closely following the celebrated pattern of sunshine and more sunshine.

Temperatures peaked in September and October, with the year’s hottest day Sept. 29 at 102 degrees (the “downtown” Los Angeles temperatures are actually measured at USC, just south of downtown). The chilliest day was Jan. 8 with a low of 39 degrees.

Nationwide, spring temperatures this year were the warmest on record, according to the National Climatic Data Center. But in Los Angeles, the March-through-May period was hardly a record breaker. In fact, for those keeping score, it was the 24th warmest since 1888.

In the words of meteorologist Steve Pryor, “This was not a very remarkable year for Los Angeles.”

“Last summer was a little warmer than normal,” said Pryor, who works for WeatherData Inc., a Kansas-based company that provides weather information to The Times. “The winter was normal and the spring was pretty close to normal.”

Normal, normal, normal. Who could complain?

Rainfall this past winter, though, was down a drop or two, though meteorologists are quick to say they saw that coming because last year was a La Nina year. On average, 15.06 inches of rain splash down on the Los Angeles Basin each year. In 1999-2000, we got only 11.57.

La Nina, a phenomenon of cooler-than-normal water in the Pacific Ocean, typically produces drier weather because it creates high-pressure weather systems that park off the coast of Central California. Winds spinning around these systems dry out by compression as they funnel down California’s coastal canyons, leading to less rainfall. This is the opposite of El Nino, which produces higher water temperatures than normal and much more rain (remember the spring of 1998?).

“We’re just beginning to understand how ocean temperatures affect weather, but it seems that the La Nina effect is among the factors responsible for the drier-than-normal weather last year,” Pryor said.

The La Nina effect is expected to end by December, and Los Angeles should get average levels of rainfall next year, according to a forecast by the National Weather Service.

And what about the greenhouse effect and global warming?

Scientists have been warning that temperatures everywhere are rising slightly but steadily because of an accumulation of gases and pollutants trapped in the atmosphere. But Pryor said there may be other reasons for a gradually warming Southland.

“L.A. has affected L.A. more than global warming,” he said. “If there’s been a slight upward tick in temperatures in the recent past, it’s because of all the urbanization, the brick and concrete that soaks up heat, the factories that are being built and all the people.”

People, no doubt, who are content in Los Angeles, for, well--what else? The normal, pleasantly predictable weather.

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Los Angeles Rainfall 1877-2000

The National Weather Service recorded 11.57 inches of rain for the season at its Los Angeles station. Rainfall is traditionally measured in cycles that run from July 1 to June 30. The Weather Service moved its rain gauge on July 1, 1999, from the Civic Center to the campus of USC.

Source: National Weather Service

Highs and Lows of the Last 12 Months

The last 12 months have seen fairly normal temperatures in downtown Los Angeles, but the year has been drier than usual. The rain measurement cycle ended June 30, with only 11.57 inches having fallen, compared with the normal 15.06 inches for the season.

Source: WeatherData Inc.

*Monthly average, 1961-90.