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| January 2007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Overview January began mild and wet, just as late December had been. But on about the 10th of the month, a strong outbreak of Arctic air brought very cold temperatures, as well as low-elevation snow. In mid-January, the entire state (and much of the western half of the U.S., in fact) saw cold temperatures and dry air. Gradually the temperatures moderated, and while conditions remained mostly dry, the temperatures rose to near-normal levels. Table 1 is a summary of monthly averages and totals at selected stations throughout the state. Table 2 lists daily temperatures and precipitation for most of the locations listed in Table 1. In Table 3, monthly and seasonal precipitation totals throughout the state are listed. Basin Summary Here is a summary of water indicators at the end of the month, by river basin:
Forecasts The Climate Prediction Center’s (CPC) forecasts for February-April appear below. Temperatures for Oregon (and much of the northern half of the U.S.) are likely to be above normal, while precipitation probabilities show equal chances of above-, near-, and below-normal.
Oregon Climate Service predicts above-normal temperatures and normal precipitation for the next three months ---basically agreeing with CPC. ENSO
Update There has been a sustained cooling of the equatorial Pacific since early December, with current SST anomalies now close to their El Niño thresholds. This is the clearest sign that the El Niño event is weakening and it bodes well for a switch towards average or wetter than average conditions across eastern Australia sometime in the late summer or autumn. In fact, we've already seen a southward extension of tropical moisture which resulted in heavy rain over the NT, SA and the western parts of Queensland, NSW and Victoria. This can be taken as a sign that rainfall patterns are beginning to change across Australia, the timing of which is consistent with that observed during previous events. In addition to the surface cooling, there has been substantial cooling below the surface; a situation that is likely to promote further weakening of the surface El Niño pattern. However, the SOI, Trade Winds and central-western Pacific cloudiness have seen their decline towards neutral values arrested somewhat during January, in association with a westerly wind burst mid-month. The westerly burst has now dissipated, so it is expected that these other ENSO indicators will continue their general trend towards neutrality over the coming months, in keeping with the weakening of the El Niño event. Furthermore, computer modeling supports the view that the El Niño will continue to decline. In Brief: I hope this doesn’t sound too “west-side-centric.” The places I list here are west of the Cascades, but much of what I describe affects the areas east of the Cascades as well. Our second snow storm of the season affected most of Oregon in early January, followed by very cold temperatures and plenty of ice. The cause was a large Arctic air mass that blanketed the area beginning Tuesday, and is probably still in place as you read this. Furthermore, the cold air went on to affect much of the rest of the country. In western Oregon, the snowfall amounts were very spotty, ranging from almost none (Albany) to 2-3 inches (Corvallis and Eugene) to much larger amounts in the Coast Range and Cascades – and even at the coast, with Manzanita and other north coast sites picking up 3-6 inches. I saw some amazing video of the north coast beaches covered with snow. Tuesday and Wednesday (Jan. 9-10) I was in Denver and Boulder, places in the news lately because of devastating snow storms which shut down Denver Airport and stranded many travelers. There was still a lot of snow there, but the roads are mostly clear and the airports are fine. Returning to Portland Wednesday evening, I was greeted by 2 inches of fresh snow and very cold temperatures, but the roads were still okay and no snow was falling -- at least, until I got close to home. As soon as I exited I-5 and got on Highway 34, the snow began to fall. It snowed harder and harder all the way to Corvallis. Arriving home, I was greeted by an inch of snow in the lowlands, but nearly 3 inches on my hill, which is only a few hundred feet above the valley floor. I was reminded once again how much snow varies with elevation, even over small height differences. Overnight, several “blobs” of moisture moved through, dropping several inches of new snow – enough to close the schools in Corvallis, Philomath, Eugene, and Lebanon. But not in Albany. The blobs bypassed Albany (and most of the northern half of the valley), to the chagrin of snow lovers. The thought occurred to me that this snow storm (and most others) is a lot like our winter rain storms. As a front approaches, winds start to blow, it gets cloudy, and precipitation begins to fall. In the case of rain storms, the fronts come from the west (southwest through northwest, actually), while Arctic “snow maker” fronts come from the north. Precipitation associated with the front is pretty uniform (higher in the mountains, lower in the valleys, but pretty similar horizontally). So Corvallis might get a half inch of rain, Albany a third of an inch, Lebanon a quarter inch – or the other way around. But everybody gets wet. In the case of snow, nearly everyone gets snow, although there might be a gradual dropoff from north to south or south to north. Wednesday was like that, with at least a dusting of snow throughout western Oregon. And then the front arrives, and everything changes. For one thing, the air gets colder, which is why it’s called a “cold front.” Wind direction changes, and humidity goes down. And the precipitation gets very spotty. In the case of rain storms, this is the “rain shower” part of the storm. And these are my favorite winter/spring days. It will rain, sometimes really hard. There might be some hail mixed in. And then the rain stops, and often the sun comes out. We are likely to see rainbows. And then later, another shower might hit. Or might not. Corvallis might get nothing, Albany a half inch, and Lebanon nothing. If you don’t like the weather, wait 20 minutes! That’s what happened Wednesday night with the snow showers. In the cold air, the clumpy “cumuliform” clouds are clearly visible on a satellite picture. That’s what I saw Wednesday evening, and figured “maybe we’ll get more snow, and maybe we won’t.” Corvallis did. Albany didn’t. Lebanon did. Salem didn’t. Philomath did. Eugene did. Clumpy, spotty snow amounts. But unlike rain storms, we could look on the ground and see which places got snow and which ones didn’t. When it comes to snow showers, there are no
secrets. Hear Ye! Hear Ye! On this Groundhog Day, February 2nd, 2007, " El Nino has caused high winds, heavy snow, Global Warming has caused a great debate, On this Groundhog Day, we think
of just one thing, On Gobbler's Knob, I see
no shadow today;
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Oregon
Climate Service
Oregon State University, Strand 326 Corvallis, Oregon 97331 Phone: (541) 737-5705 Fax: (541) 737-5710 E-mail: oregon@coas.oregonstate.edu Web: http://www.ocs.oregonstate.edu |
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