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Mild winter forecast for Pacific Northwest

Wed., June 13, 2012

Climate center predicts weak El Nino to last past fall

The U.S. Climate Prediction Center has issued an El Nino watch for re-emergence of warm water in the tropical Pacific Ocean later this year, a condition that could lead to a mild winter in the Pacific Northwest.

El Nino can bring either dry or wet conditions to the Inland Northwest, but it is consistent in bringing milder temperatures, forecasters said Monday.

It is often associated with a strengthened storm track across the southern U.S., which allows milder air to move northward.

“It doesn’t look like a strong El Nino at this point,” said Ron Miller, meteorologist with the National Weather Service in Spokane.

So far, the climate center is giving a 50 percent chance that a weak El Nino will persist into the fall and early winter based on sophisticated computer models.

Some climate models are predicting that El Nino will arise at the end of summer, while others are showing neutral ocean temperatures going into fall, the center said.

The scientists said there is a 50 percent chance that the tropical ocean will not warm up but remain normal.

Currently, the warmest water is found in the far western Pacific just south of the equator. Water to the east is closer to normal.

El Nino in the ocean can store tremendous amounts of heat energy, which causes the northern storm track to sag southward.

The last El Nino, in the 2009-’10 winter, brought only 14.4 inches of snow to Spokane compared with an annual average of about 45 inches.

“Weak, moderate or strong, they all generally lead to warmer temperatures around here,” Miller said.

The opposite phenomenon known as La Nina has influenced winter weather in the Inland Northwest in four of the past five winters.

The La Nina of 2007-’08 brought 92.6 inches of snow. A borderline La Nina the following year set the stage for all-time record snowfall in Spokane of 97.8 inches.

The latest La Nina cooling in the tropics, which occurred last winter, dissipated as of last month, and water conditions are back to normal in much of the tropics.

Last winter’s La Nina failed to bring as much snow as the three other La Nina winters.

The official weather reporting station at Spokane International Airport had 36.8 inches of snow last winter.

While lower-elevation snow was below normal, the late-running winter brought heavy snow to the mountains and contributed to high stream flows and flooding this spring.

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