La Nada begins with cooler conditions

During the fall and early winter period of 2006, our old friend El Niño formed in the waters of the south-central Pacific Ocean. El Niño is the abnormal warming of sea-surface temperatures that typically alters weather patterns across the globe.

When we were in the midst of this warm-water phenomenon late last year, the Inland Empire experienced warmer-than-normal temperatures and above-normal precipitation. But El Niño weakened rapidly this January, leading to colder and snowier, but somewhat drier, weather conditions east of the Cascade Mountains.

The latest sea-surface temperature analysis now indicates that El Niño is gone as pools of cooler waters are now forming along the equatorial regions. Both Japanese and Australian scientists say that we’re now in a “La Nada” (in-between El Niño and La Niña) pattern. Some are still predicting that a new La Niña, or cooler-than-normal sea-surface temperature event, could form sometime during the Southern Hemisphere’s winter season (our summer), this despite some areas of lingering warmer-than-normal sea-surface temperatures in the south-central Pacific Ocean.

During La Niña years, our region often experiences drier and warmer summers with cooler and wetter fall seasons. The hurricane season in the Atlantic and Caribbean waters is usually more active during this period. By contrast, El Niño patterns alter upper-level jet stream flows that become less favorable for major hurricane development. This was the case last year as a moderate El Niño led to an average tropical storm and hurricane season compared to the all-time record one in 2005, which produced an incredible 27 named storms including Zeta, which lingered in the ocean Atlantic until mid-January, the latest tropical storm ever.

Based on the fact that we’ve seen several El Niños and La Niñas within the last five years, I do expect to see that cooler-than-normal sea-surface temperature event form soon. There is no doubt that we’re seeing huge swings in sea-surface temperature patterns over a much shorter period of time. Before the 1990s, El Niños and La Niñas would typically form approximately every seven years. Now, we’re seeing El Niños and La Niñas develop within mere months of each other. This is another prime example of our cycle of wide weather extremes.

Normally during El Niño, Los Angeles and most other cities in the Southwestern U.S. see above-normal amounts of precipitation, mudslides and extreme beach erosion. This time around, however, as happens about 30 percent of the time, El Niño’s rains flooded the Pacific Northwest in a so-called “pineapple connection,” as was the case late last fall and during the fourth week of March.

Los Angeles, in turn, has seen its driest rainy season ever since last July 1. Only 2.47 inches of precipitation fell during the entire nine-month period ending March 31. That’s even drier than most stations in the Sahara Desert of North Africa for the same time span. The normal Los Angeles seasonal rainfall to date is near 13.30 inches. The previous record for least precipitation in Los Angeles at the end of March was 3.36 inches in 1976. By extreme contrast, just two years ago on March 31, Los Angeles had received a record seasonal rainfall to date of 34.86 inches, 93 percent above this year’s meager total.

I don’t see much in the way of any significant precipitation arriving in parched Southern California for at least another seven months, until early November or later. In other words, it could turn out to be the worst fire season on record in the Southwest before all is said and done.

As far as the Inland Northwest weather picture is concerned, April should turn a bit warmer and drier than usual this year due to a ridge of high pressure building in over the region. If this pattern develops, then we can expect at least a dozen beautiful sunny days by April 30.

The ridge should weaken, though, by early May. Moderate to heavy rains will be likely at times across the Inland Empire once again. Then, by mid- to late June, like last year, the rains are expected to subside and temperatures will likely rise above-normal levels for the late spring and early summer period.