It’s Official: Last Year Was Warm

With the close of the meteorological season, measured from July 1 to June 30 because of the rainfall cycle, scientists studying Los Angeles weather patterns have boiled down reams of data to two conclusions: Last year was warm and, for the most part, dry.

Tell us something we 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.

In the San Fernando Valley, temperatures soared to 100 or above on 19 days, as recorded at the Canoga Park weather station, where the highest reported temperature of the season was hit--109 on Aug. 25. The low of 31, also in Canoga Park, occurred on six dates--Nov. 23, Dec. 5, 6, 13, Jan. 7 and Feb. 24.

Three other Valley stations have filed annual reports with the National Weather Service. In Burbank, the high was 103 on Sept. 29 and the low 35 on Jan. 7 and 8. Northridge peaked at 105 on Aug. 25 and bottomed out at 36 on March 7. Van Nuys had a high of 104 on July 12 and Aug. 25, and a low of 34 on Jan. 8.

Temperatures were a bit more moderate as measured at the Los Angeles station, where the high of 102 came on Sept. 29, and the low of 39 on Jan. 8.

This year’s average spring temperature at the Los Angeles station was 63.7 degrees, the 24th warmest spring since 1888, no doubt a statistical milestone of staggering import. Compared with the average spring temperature during the past 10 years, we were down a few millimeters of mercury, with 64.6 degrees the average for the years 1990-1999.

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 forecasting company that supplies weather information to The Times. “The winter was normal and the spring was pretty close to normal.”

Normal, normal. Who could complain?

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

In the Valley, rainfall was slightly heavier with a season total of 12.6 inches recorded in Canoga Park. The rainiest month, by far, was February with 6.36. April was second with 2.7. The rainiest day was Feb. 21, with 1.97 inches.

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, typified by higher water temperatures and much more rain as a result (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 predicted to end by December. Los Angeles should get average levels of rainfall next year, according to an advanced 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 due to an accumulation of gases and pollutants trapped in the atmosphere. But Pryor said there may be other reasons for a gradual warming of the 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 with, what else, the normal, pleasantly predictable weather.

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Times staff writer David Colker contributed to this story.

(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)

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.

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Source: National Weather Service

Highs and Lows of the Last 12 Months

Burbank has seen fairly normal temperatures from July 1999 through June of this year, but those months have been drier than usual. Compaired with the normal 18.91 inches of annual rainfall, only 14.74 inches of rain fell in Burbank, slightly more than the 11.51 inches that fell in downtown Los Angeles.

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Source: WeatherData Inc.