Wednesday, July 3, 2013

El Niño weather could be forecast a year ahead

Dan Vergano and Doyle Rice: El Niño weather brings bucket-loads of rain for the West Coast, crippling drought to Australia and uncertainty to weather forecasters. But a new forecasting method may change that last part.

An international meteorology team on Monday unveiled a way to forecast El Niño weather a year ahead of time, double the lead time experts currently have. El Niños strike every decade, driven by warm Pacific Ocean water piling on the West Coast and affecting weather worldwide, triggering floods, droughts and heat. The most recent El Niño ended in 2007. A strong El Niño brings heavy rains to North and South America and drought to Australia, making its prediction something long sought by weather forecasters.

In the newly released Proceedings of the National Academy of Sciences report led by Josef Ludescher of Germany's Giessen University, a research team proposes a year-ahead forecast method that appears to get its calls right about two-thirds of the time. False alarms will happen less than 10% of the time, as well. "We study how the various locations in the Pacific are linked and how the links between them change with time," Lundescher and his colleague Armin Bunde said in a statement sent to USA TODAY.

Current National Oceanic and Atmospheric Administration forecasts of El Niño can only see ahead roughly six months, largely due to up-and-downs in spring Pacific Ocean temperatures that obscure the signal of the weather pattern developing. The current NOAA forecast doesn't see one ahead this summer, for example.

In the new study, the researchers saw that El Niño weather patterns from 1950 to 2011 were preceded by rising-temperature ripples throughout an El Niño "basin" of weather stations across the Pacific Ocean. Large-scale "cooperation" between disparate temperature bumps add up over time to produce the weather pattern. That enables their forecasts to be predicted solely from temperature data, without the use of any weather models to look ahead. "Right now, we did not find an indication that there will be an El Nino starting at the end of next year," Bunche says, by email....

NOAA image of December 1997 El Nino

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