El Niño to La Niña transition means more rain, slow crop development

By TIM HEARDEN

Capital Press

As opposing weather patterns have been battling in the Pacific, the West -- and much of the country -- has borne the brunt of the artillery.

El Niño's strong southern storms are rapidly giving way to La Niña, marked by unusually cool equatorial ocean temperatures that tend to push storm systems north.

That transition has led to a wet spring that's hampered crop development in much of the West, and also caused farm-flustering unsettled conditions in parts of the Midwest and South.

The way things are heading, the Pacific Northwest could be in for a wet upcoming winter, said Ed O'Lenic, chief of the operations branch at the U.S. Climate Prediction Center in Washington, D.C.

"A La Niña is in the process of developing right now, and we are expecting it to continue into the fall and winter," O'Lenic said. "That's not a 100 percent. ... There's probably a 70 percent chance that it's going to continue into the winter."

Last winter was unique, O'Lenic said, in that it featured an unusually long period of arctic oscillation -- an atmospheric condition in which pressure over the polar region clashes with that over middle latitudes.

"We've not often seen that simultaneous with a strong El Niño," he said.

The conditions were marked by a very strong storm track across the South and mid-Atlantic states, with cold air close to the storm track, causing heavy snows.

"It was really an extremely unusual winter in that regard," he said.

In the West, a persistent parade of rain clouds and cool temperatures broke precipitation records while causing headaches for numerous commodities. Among them:

* Weather has delayed and damaged first-cutting hay throughout the West, which will widen the price gap between top- and poorer-quality hay.

* Wet conditions have caused common diseases such as brown rots, scabs, blossom blights and leaf spots to flourish on a variety of fruit crops.

* Rain ruined a large part of the last half of the California cherry harvest, delayed rice planting in the state and will contribute to lighter harvests of tomatoes.

El Niño brought better-than-average rainfall and snowfall to many parts of California, filling reservoirs and helping the state emerge from a more than three-year drought.

The cool and wet conditions helped navel oranges enjoy one of their best years ever. But for some other crops, it caused plenty of uncertainty.

Greg Thompson, general manager of the Prune Bargaining Association in Yuba City, Calif., recalls what happened with dried plums as a result of the strong El Niño of 1998.

"We thought we had 170,000 tons and ended up with 103,000," Thompson said. "We had a lot of drop, a lot of disease problems that year. That was a more severe El Niño than we're having this year ... but we're a little cautious because it's the same kind of weather pattern that fooled us before."

A barometer of the strength of either an El Niño or a La Niña is to look at Northern California, where a strong season of either will bring heavier-than-normal rain and snow.

"Any kind of La Niña statistically has a wetter result in the Pacific Northwest," said Kathy Hoxsie, a National Weather Service warning coordinator in Sacramento, Calif. "As the signal gets stronger and stronger, its influence broadens."

The long-term forecast for Northern California is for relatively normal precipitation and temperatures, Hoxsie said. Thus, any La Niña that takes hold over the coming months may not be all that ferocious.

A wild card, she said, is the fallout from the volcanic eruption in Iceland, which will probably result in slightly cooler temperatures.

"We came out of El Niño very quickly," Hoxsie said. "It still remains to be seen whether we'll plateau at neutral or a weak La Niña or dive into a strong La Niña. ... If we continue this trend of a moderate to strong La Niña, we could have another wet year."

Rainfall totals

Here are the seasonal rainfall totals and comparisons to normal for selected Western cities, according to the National Weather Service. Totals are as of June 29:

Seattle-Tacoma, Wash.: Season to date 39.51 inches (normal 33.55 inches)

Spokane, Wash.: Season to date 15.44 inches (normal 14.44 inches)

Portland, Ore.: Season to date 35.06 inches (normal 33.69 inches)

Pendleton, Ore.: Season to date 14.41 inches (normal 11.12 inches)

Medford, Ore.: Season to date 15.11 inches (normal 17.52 inches)

Twin Falls, Idaho: Season to date 8.08 inches (normal 9.65 inches)

Sacramento, Calif.: season to date 20.74 inches (normal 17.93 inches)

Fresno, Calif.: season to date 12.36 inches (normal 11.23 inches)