An unusually strong El Niño will affect vast swaths of the United States this winter, possibly including heavy rains across all of parched California.
National Weather Service forecasters said Thursday that this year's expected El Niño could bring heavy rains to just about the entire state of California, including northern regions where less rain had previously been forecast, according to the Los Angeles Times.
The El Niño Southern Oscillation is the periodic warming and cooling of the Pacific Ocean away from its average temperatures. La Niña is the cooling phase, and El Niño is the warming phase.
The current El Niño pattern is expected to be a "strong" one, meaning climate researchers expect it to bring a lot rain to California and other erratic weather to other parts of the country, especially in the southern regions.
This is important, since the state depends heavily on water drawn from Sierra Nevada snowpack, in the northern half of the state. California's two largest reservoirs, Shasta Lake and Lake Oroville, are in also in the north.
Some are comparing it to the unusually strong El Niño of 1997, which brought severe weather events including flooding in the Southeast, an ice storm in the Northeast, flooding in California, and tornadoes in Florida, according to a NOAA report from 1998.
"This El Niño continues to rank among the strongest in our records, which start in 1950," wrote Emily Becker, on NOAA's ENSO Climate blog on October 8.
This is a breakdown of what NOAA said on Thursday that it expects to see this winter:
- "Wetter-than-average" conditions across the southern tier of the United States, from Southern California, to Texas, to Florida, and in southern New England
- Drier than average weather in Hawaii, central and western Alaska, parts of the Pacific Northwest and northern Rocky Mountain region, as well as the Great Lakes and Ohio Valley.
- It will be warmer than usual in the Northeast, and colder in the Southeast.
It is important to point out, as Becker does in her blog, that long-term climate forecasts are far less certain than short-term weather forecasts. These are expected conditions, not guarantees.
But, as she notes, there are some striking patterns that accompany El Niño. For example, "Boulder, Colorado, has registered seven October snowstorms with more than one foot of snow since 1950, every one happening during an El Niño winter," she wrote.
While the rain will bring some relief to California's multiyear drought, NOAA's Mike Halpert cautioned against excessive optimism.
"While it is good news that drought improvement is predicted for California, one season of above-average rain and snow is unlikely to remove four years of drought," said Halpert, in a press release issued by NOAA. "California would need close to twice its normal rainfall to get out of drought, and that's unlikely."