Wednesday, December 14, 2005
Way Below Normal December Regarding Temps...
We are averaging 36.2 on my weather station for the month of December. Thats Cold!! And whats even more weird about that is, we are under the influence of a High Ridge that has been persistant. Usually when you get High Ridges, you warm up pretty good and stay generally clear. Our low this morning got t0 21! Now, this does remind me of last year and I am not starting to get worried, but not too much though because most models now agree to break the ridge down and go zonal by day 8. This has been a weird winter (or fall) so far, only makes you wonder "whats next?"
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Actually, temperatures have been consistently below average in Northwest Oregon and Southwest Washington since September! In that regard, this year is way different than last year. Even the average temp at PDX has been a chilly 37.1, over four degrees below average for December. At my house in Orchards, WA our high so far this month is 41, with most days staying the the upper thirties with lows in the upper teens. The thing about high pressure is, it's not always necessarily conducive to a warm event. Just ask folks out in the plains, they will have arctic high pressure slide down from interior Canada and keep their highs well below zero, despite bright blue skies and sunshine. That's kind of what's happened to us for the past couple weeks, but to a lesser degree. Last year, the nation got plenty of these arctic highs, but they always slid down the East side of the Continental Divide. This year, thanks to a ridge axis that has been just off our coast, these arctic air masses have been allowed to get further west than usual, allowing the bitter cold air to spill over both sides of the divide, giving Eastern oregon and Washington their highs in the teens and twenties and lows in the zeros and negatives that they've seen of late, and also our very cold weather. You see, the kind of weather one gets from high pressure all depends on the position of the center of the high. Rotation around high pressure is clockwise, so the east side of a high can be bitterly cold, while the west side is usually much milder with warm southwesterlies at the lower levels. Last year, the high was always centered in the great basin, giving us the mild southerly flow on its western flank. So all in all,this pattern is actually a vast improvement from last year. Just look at the 125% of normal mountain snowpack! Another trend I've noticed is that there has been a gradual retrogression of this ridge ever since it set up in early November, allowing more and more cold air to spill into our region, just look at this morning. I really don't know why everyone's whining so much, i love this cold weather, and this is nothing like last year. Everyone should go check out the waterfalls in the Gorge, they're almost frozen solid!
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