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A Gusher of Moisture Hoses California. Is El Niño Here?

ImaGeo iconImaGeoBy Tom YulsmanDecember 3, 2014 12:59 PM


Sign up for our email newsletter for the latest science news Parts of drought-plagued California got hosed by a gusher of moisture streaming up from the tropics on Tuesday. As the chief meteorologist for Minnesota Public Radio put it, the copious stream of water vapor looks a whole lot like a "pineapple express," a low level jet of moist air flowing from Hawaii to California. This is a phenomenon that tends to occur during El Niño winters. You can see it in the animation above, made up of images from the GOES-15 weather satellite. Look for the broad streak of cloudiness that streams up from the tropics to southern California. In this case, the moisture is coming from the tropics a bit south of Hawaii. But I'm sure Californians are grateful for the moisture regardless of the exact source.


An animation of total precipitable water in the atmosphere over the eastern Pacific shows moisture streaming toward California from the tropics. (Source: CIMSS) Here's another view of that gusher — this one showing total precipitable water, a measure of moisture in the atmosphere. In the animation, redder colors depict moister air. Note that counter-clockwise vortex off the California coast. This is a low pressure system that has been sucking up moisture from the tropics and aiming it at Southern California. During Tuesday afternoon, the gusher dumped a half inch of rain per hour on the Los Angeles area, and up to five inches in the nearby mountains. This is welcome relief from profound drought conditions, although the National Weather Service is warning about the potential for mudslides. Is this a symptom of El Niño finally dawning — after months of anticipation? The National Oceanic and Atmospheric Administration has not yet made it official. But it may well in its regular monthly ENSO update later this week. Although NOAA has yet to weigh in, the Australian Bureau of Meteorology did on Tuesday, in a press release:

Some El Niño-like impacts have already been seen this spring in Australia and several regions around the globe, including Asia, South America and southern Africa.

Moreover, conditions in the tropical Pacific are looking more and more El Niño-ish. For example, tropical Pacific Ocean temperatures have exceed El Niño levels for a month. As the bureau put it:

Many climate indicators remain close to El Niño thresholds, with climate model outlooks suggesting further intensification of conditions remains likely. The Bureau’s ENSO Tracker status is currently at ALERT, indicating at least a 70% chance that El Niño will be declared in the coming months. Whether or not an El Niño fully develops, a number of El Niño-like impacts have already emerged.

That said, the atmosphere isn't fully dancing to the ocean's tune yet, indicating that "a typical El Niño ocean–atmosphere interaction may not be fully locked in." At least not yet.


Seven-day forecast of precipitation totals, in inches. (Source: National Weather Service) Whether El Niño is declared or not, the map above is very good news for California and other parts of the West afflicted by drought. It depicts forecast precipitation totals over the next seven days. Check out that big stripe of orange over the northern Sierra Nevada mountains in California. The "X" marks the spot of a predicted 8 inches of precipitation. That should really help snowpack. Let's hope this forecast comes true — and that the precipitation keeps coming, regardless of whether El Niño finally is born.

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