Emerging weather pattern could break California's drought
By MATTHEW WEAVER
Meteorologists anticipate a moderate El NiÃ±o will bring drier winter weather to the Pacific Northwest and wetter weather to California, possibly ending a three-year drought there.
El NiÃ±o is characterized by ocean temperatures about 2 degrees above average across the central and eastern Pacific Ocean, which makes it a weaker event, said National Oceanic and Atmospheric Administration Climate Prediction Center Deputy Director Mike Halpert during an Oct. 15 press conference.
Forecasters expect El NiÃ±o to strengthen in the next few months, peaking at a moderate-strength event, Halpert said.
"Impacts from moderate-strength El NiÃ±os tend to be less consistent than those from strong ones, but this event is still anticipated to be the dominant climate factor influencing the upcoming winter," he said.
The administration's winter seasonal forecast, covering December through February, favors warmer and drier than average conditions across the northern half of the United States, and wetter and cooler than average conditions across much of the southern half.
Precipitation is most likely to be above average across the southern part of the nation, from California to Florida, with the best chances for a wetter than average winter in Texas and Florida.
Precipitation is likely to be below average in the Pacific Northwest, he said.
NOAA forecasters said California is slightly more likely to be wetter than average.
Halpert said El NiÃ±o will bring relief to drought conditions in Texas. California has also been locked in a three-year drought, he said.
Louis More, public affairs spokesman for the Mid-Pacific region of the U.S. Bureau of Reclamation, said any wet weather is welcome. The bureau manages federally owned reservoirs around the West. The storms that marched through California recently produced a significant amount of rain for the region.
"We're talking about an earth that is dry for three years for the most part taking that water and completely absorbing it in no time flat," he said.
Ideally, the region would experience a series of consistent storm systems over time, to maintain water storage, More said.
But he's not encouraged.
"We're looking out there in the forecast, and you can see it's still looking pretty dry," he said.
"If it's going to be a wet year, that's something the grower is going to have to be cognizant of," California Wheat Commission Executive Director Bob Falconer said, adding that stripe rust is typically worse during wetter winter years.
Bob Curtis, Almond Board of California associate director of agricultural affairs, said orchards want to replenish their soil profile with water.
"You want to start off the season with a full soil profile," he said.
El NiÃ±o pattern will take hold as the fall and winter progress, NOAA's Halpert said, adding that individual storms or daily or weekly systems vary through any season.
Snow is not forecasted by the center, he said.
"It's very difficult to draw the conclusion that cooler and wetter results in more snow, especially as you get down into the South," Halpert said. "That really becomes a matter of timing."
Adequate snowpack in the mountains is the key to maintaining adequate water supplies for irrigators throughout the West.
Halpert said the service's forecasts generally are right about 50 percent of the time in looking at the country as a whole, with precipitation forecasts a little less. In El NiÃ±o years, the service's forecasts are a little better than that, particularly during strong El NiÃ±os.
"It's hard to say how this one will end up faring," he said, adding that seasonal forecasting is still in its infancy.
Ted Day, hydraulic engineer for the Pacific Northwest regional office of the Bureau of Reclamation, said his office doesn't need a wet winter to catch up, as the region's reservoir carryover levels are in good shape.
"The El NiÃ±o forecast doesn't mean it will be dry, it just means there's a slightly better chance it could be dry," he said.
A wetter, cooler La NiÃ±a would be preferred in the forecast, Day said, but it's too early to be concerned. He advises farmers to track the snowfalls coming in.
"We like to say, wait until January before anyone gets too excited," he said. "Although you don't want to see November and December go by without getting a start to the winter snowpack."
Matthew Weaver is based in Spokane. E-mail: email@example.com.
Access the NOAA Web site at www.noaa.gov.
What is El NiÃ±o?
The Pacific Ocean's warmer waters are usually west of the international date line, where most tropical rainfall occurs. When El NiÃ±o develops, the warmest waters shift to the central and eastern part of the ocean.
The tropical rainfall follows the warmest water. When the heat source moves, it transfers the heat from the ocean to the atmosphere, which warms the jet stream that crosses the ocean and North America.
"When we see this shift in rainfall into the central Pacific, we see the jet stream become stronger than average and also shift equatorward," said National Oceanic and Atmospheric Administration Climate Prediction Center Deputy Director Mike Halpert. "That's why we end up with increased storminess across the south and a tendency for dryness across the north ... and the Pacific Northwest."