‘La Nada’ could lead to severe, unpredictable weather

(VOA) Unpredictable and extreme weather is likely to persist until the spring of 2014 because of the lack of El Niño or La Niña patterns in the Pacific Ocean, according to new sea height data collected from NASA’s Jason-2 satellite.

The so-called “La Nada” event has stubbornly persisted for 16 months and indicates “near normal sea-surface height conditions across the equatorial Pacific Ocean.” During El Niño episodes, the water level rises because of warmer water temperatures. During La Niña periods, the opposite is true.

“Without an El Niño or La Niña signal present, other, less predictable, climatic factors will govern fall, winter and spring weather conditions,” said climatologist Bill Patzert of NASA’s Jet Propulsion Laboratory, Pasadena, California. “Long-range forecasts are most successful during El Niño and La Niña episodes. The ‘in between’ ocean state, La Nada, is the dominant condition, and is frustrating for long-range forecasters. It’s like driving without a decent road map — it makes forecasting difficult.”

For the past several decades, about half of all years have experienced La Nada conditions, compared to about 20 percent for El Niño and 30 percent for La Niña, according to NASA.

Patzert noted that some of the wettest and driest winters occur during La Nada periods.

“Neutral infers something benign, but in fact if you look at these La Nada years when neither El Niño nor La Niña are present, they can be the most volatile and punishing. As an example, the continuing, deepening drought in the American West is far from ‘neutral,’” he said.