Look for 'normal' winter conditions

A standing-room-only crowd packed into the auditorium at the Oregon Museum of Science and Industry in Portland on Saturday, November 17, to hear what regional meteorologists and climate experts had to say about the kind of weather we might expect this winter here in the Pacific Northwest.

The event was the 20th annual winter weather forecast conference put on by the Oregon Chapter of the American Meteorological Society.

Participating speakers were Clinton Rockey, National Weather Service; Kyle Dittmer, Columbia River Inter-Tribal Fish Commission; George Taylor, Applied Climate Services and former climatologist for the state of Oregon; and Jim Little, Oregon Department of Forestry.

The single most reliable indicator when it comes to forecasting our winter weather is the El Niño/La Niña Southern Oscillation (ENSO) signal in the tropical Pacific Ocean.

El Niños result in warmer and drier winters here, while La Niñas tend produce cooler and wetter conditions. Forecasters consider the phenomenon to be 65 to 75 percent accurate as indicator.

During the past two winters La Niña has been in control - and the weather was indeed cooler and wetter than normal, mostly late in the season. La Niña is gone now, and is being replaced by...what?

What looked like a developing El Niño signal late last summer has surprised most forecasters by fading to neutral throughout the fall. And the current thinking is that this neutral state will persist through the winter. So, what does that mean for us?

A neutral ENSO signal usually means temperatures and precipitation close to average for the winter as a whole. But it can also mean more variable and changeable types of weather.

For the period December through February, National Weather Service meteorologist Clinton Rockey sees average temperatures and slightly drier conditions, except for February which may be slightly wetter than normal. He also stresses the weather should be highly variable. Dittmer is expecting normal temperatures November through March, with average precipitation for November, January, and March, but below-normal values in December and February.

Taylor is going with a stormy first half of November then a drier second half. December and January will be dry, mild and relatively quiet. He expects February to be more active, with above-normal precipitation levels and slightly cooler conditions. For March, he simply says "wet, windy and wild."

Little wrote his own computer program to analyze several types of climatological indices, not just the ENSO. Little's results show that December should be average with regard to both temperature and precipitation, while January is seen to be cool and wet. Normal temperatures are predicted for February and March, with dry conditions in February tending to normal precipitation levels in

March.

Little also sees a normal snowpack in the northern Cascade Mountains.

Last winter, residents of the Pacific Northwest were spared the discomfort of a significant cold snap. Three of the four prognosticators think there is an increased chance of at least one arctic-air outbreak this time around, with Dittmer being the lone dissenter.

Because of the weak ENSO signal this fall, there's not quite as much agreement among the forecasters than there has been over the past two years. But there is a general theme.

The period November 2012 through March 2013, taken as a whole, should come in about average with regard to temperature and precipitation. It's important to remember, however, that these normal values can be achieved by experiencing relatively unchanging weather that tends to hug the mean pretty much throughout the winter, or by wild swings about the mean caused by highly changeable

weather.

Which way will it go for us this winter?

We're all about to find out.