El Nino packs a punch far beyond soggy California
A periodic climate phenomenon, El Nino has prompted storms to smack southern California this week rather than the Pacific Northwest. But Indonesia and parts of Australia are also affected, except they're too dry.
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Much of the weather-related attention in the United States focuses on the Golden State, where a series of storms this week have dumped between 8 and 10 inches of rain in the mountains around Los Angeles. States of emergency were declared in five counties – three in southern California.
But forecasters note that the effects of El Niño and its La Niña counterpart, which constitute a see-sawing climate phenomenon in the tropical Pacific, touch virtually every continent.
Its influence on global weather patterns on seasonal time scales "far dwarfs everything else we've got," says Mike Halpert, deputy director of the National Oceanic and Atmospheric Administration's Climate Prediction Center in Camp Springs, Md.
This El Niño's ranking: top third for strength
As measured by NOAA criteria, the current El Niño, which arrived last July, has nudged its way into the "strong" category, Mr. Halpert says. Although it is far weaker than similar events in 1982-83 and 1997-98, the current El Niño's intensity places it among the top third of all El Niños since 1950.
El Niño is an unusually deep warm pool of water that builds in the tropical western Pacific, then migrates east toward the west coast of South America. Warm, moist air rising off that pool triggers the formation of thunderstorms, whose strong updrafts represent a crucial part of the atmosphere's heat pump –drawing warm air from the tropics up and toward the poles, where it cools, sinks, and circulates back toward the equator.
The change in location for that vigorous, widely spread region of convection from west to east in turn alters atmospheric circulation patterns. As the circulation patterns shift, so does the distribution of heat and moisture.