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La Nina brings wet weather to Northwest

Published: May 24, 2010, 12:00am

Weary of the wacky weather, woeful weeder, er reader?

Seems like we’re getting cheated on our hopes of a -sunny May.

Vancouver’s Steve Pierce has some answers on just how lousy it’s been.

“So far this month at Vancouver’s Pearson Airport, we are below normal on temperature and above normal on precipitation. If this wet trend continues, we may end up seeing the first back-to-back wetter-than-normal months in Vancouver since the fall of 2007.”

Not only wet but cold.

“Several deep troughs of low pressure have set up shop over the Pacific Northwest over the past 10 days, with what seems like endless cloudy, cool and wet weather. That also includes windy weather as well. One of the storm systems last week brought winds to the coast reminiscent of a midwinter storm with gusts to 70 mph.”

What’s causing all this?

“El Nino, which is marked by warmer-than-normal ocean water in the tropical Pacific near the equator, was the reason why January and February were so quiet weather-wise. Once last winter’s El Nino faded by March, we returned to more normal conditions. However, since then, the opposite of El Nino (known as La Nina) appears to be quickly taking shape. A La Nina is marked by cooler-than-normal waters in the tropical Pacific. The effect on Pacific Northwest weather, in a La Nina, is typically cooler and wetter than normal. These two phenomena wax and wane every few years, usually with a neutral year mixed in between. However, every now and then, we get a La Nina that follows right on the heels of an El Nino and the result can be some pretty wild weather. Look no further than out your front window for a great example,” Pierce wrote in an e-mail.

Don’t we generally get some heat in May?

“Looking back over historical records at the Portland International Airport, it is rare that we get all the way through May without seeing a single high temperature of at least 80 degrees. In fact, currently we have only made it as high as 76 degrees this month. … At this point, I do not see any change in the current pattern until at least the holiday weekend, and maybe longer. Another system will pay us a visit Tuesday, followed by more showers for the second half of the week. Below-normal temperatures will again be the rule for most, if not all, of the coming week. But, all of this is not so bad. The Cascades continue to pick up low-elevation snow that was not falling during the winter. Many of the area reservoirs are filling up and that is a good sign that a drought may not be in the making this summer. Droughts have been known to occur after an El Nino winter.”

Pierce is the executive vice president of the Oregon chapter of the American Meteorological Society.

You want it warmer? Pierce suggests heading east.

“Most locations on the East Coast are running as much as 10 to 15 degrees above normal lately. New York City will see plenty of sunshine with temperatures into the 80s most of this week,” he predicts.

But, hey, if you can’t go to the Big Apple, try a Wenatchee apple.