High winds part of unusual winter -- maybe

MAT-SU -- Every driver in the Valley has felt it over the past several weeks -- you're driving your car along one of the highways in the area and suddenly your tires are over the white line, or worse yet, over the center line. Your aerodynamically designed vehicle has just been given a shove by Mother Nature.

The Valley has been under strong wind advisories for nearly two months, according to information from the Anchorage office of the National Weather Service. Winds strong enough to snap power lines in the Knik River area Saturday night raged around Hatcher Pass Monday night, battering hard enough to knock down the log sign at Hatcher Pass Gateway Center.

"We've had wind warnings out, by and large, for most of the high-terrain areas of Southcentral more often than not for the last two months," said Carven Scott, a science officer with the National Weather Service. "We're just in a pattern such that the jet stream is pretty much out of the south -- a tropical jet stream fairly perpendicular to the mountains, causing downsloping winds."

The winds, along with the unusually warm weather, appear to be effects of what Scott said is a interdecadal weather pattern changing.

"This is very unusual, for November to have no snow on the ground and to have this kind of subtropical jet laying over us," Scott said.

Scott said the weather shift is larger than the El Nino, La Nina pattern. Those two, he said, bring about changes in weather because of a warmer than normal bubble of water in the ocean -- El Nino -- followed by a colder than normal bubble of water, La Nina. Although those two weather anomalies are cyclical, their cycles generally begin and end in a span of just a few years. This larger weather pattern, Scott said, is part of a 20- to 25-year cycle called a North Pacific Oscillator.

"We're transitioning from what had been a warm Pacific Ocean … back into a colder Pacific Ocean," Scott said. At the same time, El Nino is making itself known again, which means warmer, wetter weather. When the two happen at the same time, it could mean weather similar to that seen in the winters of 1976 and 1977.

Could is the operative word. Scott stressed that he and others at the National Weather Service do not make long-range predictions.

"The National Weather Service generally focuses on short-term [predictions] -- seven days and under," Scott said.

And, in the short term, it appears winter may be on the horizon.

"It appears that pattern is breaking down," Scott said of the warm, tropical weather current that has been gusting around the Valley. "If the long-range computer models are correct, it may shift into a more normal pattern toward next week."

If Scott sounds hesitant, it's with good reason. Twice this fall, he and others at the service have predicted the weather would return to normal. And twice this fall, he and others at the service have been proven wrong by Mother Nature. In fact, Mother Nature has had more than one laugh at the scientists.

"We've just had the second 100-year storm on the Kenai Peninsula within three weeks of each other," Scott said, referring to the heavy rains that have washed out roads and bridges twice in the past month. One-hundred-year storms, he said, are so named because they generally happen only once in a century. In addition, Anchorage had the wettest October on record, and the fourth-warmest in 100 years. "There's a lot of things going on, from a statistician's standpoint of view, that are two or three deviations away from normal."

It all boils down to one fact -- it's ultimately very difficult to tell in the present what the weather pattern means.

"I'm sure we will be doing post-mortems on this for two or three years," Scott said. Looking back is one of the best ways, he said, to learn how to predict future weather activity. Weather is generally cyclical, but scientists still have limited knowledge when they look at history. Weather data only goes back a hundred years or so, although weather has been affecting lives for thousands of years. But looking back over that relatively short history, he said, is one reason he believes the warm weather Mat-Su has been feeling lately is about to come to an end.

"Warm Octobers are generally followed by warm Novembers," Scott said. "And those are generally followed by normal or below-normal Decembers."

Scott guessed lower temperatures would begin over the weekend, with winter settling in for good the week after Thanksgiving.

"I think we feel fairly confident that Saturday and Sunday will begin the colder pattern," Scott said, "if the last 100 years is any indication."