Monday, June 28, 2010
El Niño has ended, but climatologists are reporting its colder cousin is setting in. KPBS reporter Susan Murphy explains why La Niña could mean a dry year for San Diego.
Climatologists say San Diego and the entire southwestern United States can expect dry conditions this fall and winter because El Niño has ended and La Niña is setting in.
El Niños and La Niñas are weather cycles detected from sea-surface temperatures in the central Pacific Ocean. El Niños usually bring wetter than normal winters to San Diego. La Niñas typically bring drier, and warmer conditions.
Last year, El Niño was credited with bringing San Diego near-normal rainfall. But that followed some of the driest years on record.
David Pierce, a climate researcher at Scripps Institution of Oceanography said a La Niña is bad news for San Diego’s water supply.
"That’s not good for San Diego because as you know we’re under water restrictions right now and we need all the water we can get," Pierce said.
Pierce said the region will start seeing the drying effects beginning in September and lasting through at least next March. "So we’ll see it before next year. But the effects tend to linger because when you have a dry year, the reservoir levels drop and you’re affected by that for some time," Pierce explained.
Pierce said La Niña has not officially begun because it's a process with several months of specific temperature thresholds, but the trend is obvious based on satellite and ocean measurement data.
Pierce said La Niñas typically last six to nine months, and could worsen the wildfire danger if it doesn’t rain before the Santa Ana winds arrive.
The last lengthy La Niña, from 1998 to 2001, helped cause a serious drought in much of the West, according to National Oceanic and Atmospheric Administration.