Potential El Nino might bring relief to California drought
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WASHINGTON, Aug. 13, 2015 - A potentially historic El Nino event could be helpful to those in Southern California facing historically dry conditions, but experts say it's too early to tell how much assistance - if any - the system will give the drought-stricken state.
In a call with reporters Thursday, National Oceanic and Atmospheric Administration officials said they are expecting a strong El Nino in the fall and winter with effects of the event lasting into the spring months.
The Climate Prediction Center on Thursday put the chance of an El Nino event at greater than 90 percent with odds that it will carry into early spring at 85 percent. In fact, Mike Halpert, deputy director for NOAA's Climate Prediction Center, said it “could be among the strongest El Ninos in the historical record,” which dates back to 1950.
However, Kevin Werner, NOAA's director of western region climate services, said there is no correlation between an El Nino event and added precipitation to the central and northern parts of the state, which have critically low levels of snowpack to feed rivers downstream. He also noted that although El Nino events typically bring precipitation to Southern California, there's no guarantee of that either.
“It's important to bear in mind that the correlation between El Nino and precipitation are far from perfect, even in places with relatively high correlations such as Southern California and Arizona,” Werner said. “There are examples from the recent past where El Nino events were drier than average in these places.”
Halpert said forecasters will have a better idea of the role that El Nino might - or might not - play in adding precipitation to California as the event develops into the winter months.
The four-year drought event has left the central Sierra Mountains with 71.3 inches less of precipitation than normal, a shortage that would take 2.5-3 times the average annual precipitation to achieve full recovery in one year. The wettest year on record is 1983, which was about 1.9 times the average annual precipitation.
El Nino develops when trade winds typically forcing warm surface water in the Pacific Ocean at the equator to the west toward Australia and Asia cease, bringing the warmer water to the east along the South American coast. The warmer water alters the jet stream over North America, typically bringing storms and added precipitation to parts of the southern U.S. and keeping arctic temperatures at bay in the North.
Halpert noted that temperature measurements along the “Nino 3.4 region” in the east-central equatorial Pacific could reach a seasonal average of 2 degrees Celsius above normal, something that has only happened once before in the 1972-1973 El Nino event. That same threshold was topped in 1982-1983 and 1997-1998 events, but was not the seasonal average.
Much remains to be seen about the El Nino event: whether or not it will actually happen, whether the potential for added precipitation will give California nourishing rain or dangerous mudslides, and what it will mean for adding to historically low snowpack. But Werner said precipitation will be critical to getting California - and other parts of the western U.S. currently in drought status - some relief.
“Precipitation for the upcoming winter will be extremely important for (California's) water resource situation. At this point, there's a lot of uncertainty,” Werner said. “A single El Nino year is unlikely to erase four years of drought.”
According to the most recent Drought Monitor from the National Drought Mitigation Center, most of Arizona, California, Idaho, Nevada, Oregon, Utah, Washington, and western Montana and New Mexico are currently in moderate or exceptional drought.
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