Mid-winter Dry Spell

Last summer I predicted a “wet, windy and wild” winter. That prediction has been somewhat  true, but for the last two weeks we have seen a “mid-winter dry spell” – something that happens just about every year. Even in wet winters.

In fact, fall and winter have been wet. December, with more than 10 inches, was particularly rainy. Since September, we (mid-Willamette Valley) are about 2 inches ahead of our long-term average, or “normal.” It hasn’t been particularly cool, due to the lack of serious Arctic outbreaks, but active winters tend not to be especially cool. Even January, which was rather dry overall, had flooding in mid-month.

You have probably noticed that the Midwest and East Coast have been having a rough and very snowy mid-winter, even as we have our dry period. Again, this is not surprising. Consider this:

A “ridge” is an elongated area of generally high air pressure, while a “trough” is an area of low pressure. Generally, a ridge is associated with dry (and often warm) weather, while a trough tends to produce stormy, and often wet and cool, weather.

If you had a weather map of the US tracing lines of equal air pressure, you would see a pattern that looked like waves. The crests, or high points, are ridges; the low points are the troughs. That pattern would continue around the world, with four or five ridges separated by four or five troughs. If these are evenly spaced, that means that if a ridge is over the western US, a trough is affecting the eastern half of the country.

And that is exactly what is happening now. While we enjoy dry weather, the eastern half of the country is getting pummeled by very active weather systems. And it’s as if things are stuck in place: “our ridge” for the last two weeks and “their trough” over that same period.

And not just in the Midwest and East. In the Southwest, “Frigid weather in the U.S. Southwest choked natural gas supply on Friday as frozen wells starved pipelines. Analysts estimated that between 3 billion and 5 billion cubic feet per day of natural gas supply was shut in due to the weather over the past couple of days.” (Reuters, Feb. 24, 2011)

In Dallas, Texas: “An overnight snowstorm brought air and ground traffic to a near standstill in the Dallas area Friday, frustrating thousands of fans trying to get into town for Sunday’s Super Bowl.” (Washington Post, Feb. 4, 2011)

Farther north, in places that EXPECT cold winter weather, it has been brutal. In Chicago, “Snowmageddon 2011 has brought much of Chicago’s business to a standstill.” (BusinessWire.com, Feb. 4, 2011). “Snowmaggedon” even had unusual “thundersnow” (thunder is rare during big snowstorms).

Cleveland’s WKYC said this: “The month of January 2011 will go down as the second month in a row where temperatures were below normal across northeast Ohio, unlike much of 2010. The month of January was 2.6 degrees colder than normal with a daily average temperature of 23.1 degrees. In comparison, during an El Niño spell when ocean waters are warmer, January 2010 was 1.4 degrees above average.”

Then they said “A stronger La Niña pattern in the Pacific Ocean is partly to explain on how the tide of fortune has changed in our weather since November, according to meteorologists who study climate change.”

Exactly! Just as La Niña is responsible for our generally wet winter, so it has brought extreme cold and plenty of snow to places like Chicago and Cleveland. And last winter was mild and relatively snow-free in the Midwest, and dry here, due to El Niño.

Now let’s look ahead. The Climate Prediction Center’s forecast for the Northwest for February-April calls for cooler than average temperatures and average precipitation (see below). Mine is different: above-average temperatures and below-average precipitation. A far cry from last year’s cool-wet spring.

In a few months we’ll know who is right!


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2 Responses to Mid-winter Dry Spell

  1. W7ENK says:

    ” … last winter was mild and relatively snow-free in the Midwest … ”

    I beg to differ. Last winter saw much the same conditions as this winter across the Eastern 2/3 of the U.S., albeit not quite as bad as this year. This is the second winter in a row that has seen crippling snowstorms along the Eastern Seaboard, ungodly frigid temperatures in the Central and Upper Midwest, “rare” snow and ice storms in the deep South, etc…

    Case in point: Early in the second week of January 2010, it snowed in Orlando while Key West saw a high temperature of only 43 degrees with a strong Northerly wind, and night time temperatures in the Keys were flirting with freezing – so cold in fact that the Red Cross opened shelters to house residents, some of whose homes have no windows! We traveled there for our mother’s 60th birthday (1/8) to escape the dark and depressing, cool, wet and dreary grey skies of the PNW, only to discover that it was actually warmer and sunnier in Seattle on that day. Whoops!

    At the beginning of this winter, a friend in Central Ohio was telling me she didn’t expect much if any snow this year since they had so much last winter… Boy was she wrong! Just this morning she was complaining about waking up to even more snow – yet again.

    And one last point (not entirely clear on this one, I’ll be honest): I recall hearing that International Falls, MN set a record low temperature last winter of something like -37°F, which of course was broken this winter by a low only a couple weeks ago of -43°F.

    We won’t even begin talking about Norther Europe and the last two winters they’ve experienced…

    I see every indication that this pattern is going to continue to hold, and won’t break down for another few weeks, at which point it will be too warm to produce snow in the PNW lowlands, though timing will be perfect to give us a dark and depressing, cool, wet and dreary grey spring, just like last year.

    I hope I’m wrong.

  2. Mark Spence says:

    Your predictions for this winter are wrong in many respects, and the weather has been far more peculiar than you let on in this blog. This winter has seen very pronounced El Nino and La Nina weather patterns. The ferocity of the weather in the eastern third of the continent is also highly anomalous. Your analysis and predictions are primarily based on finding analogs with past seasonal developments. What I’d like to see you do in this blog is explain why, and where, your predictions have failed. Your writing never conveys a learning process: it is too often just predictions, defenses of those predictions, and explanations of how anomalies fit those predictions.
    This winter cannot really fit anyone’s models, and honestly trying to understand why is by far the most valuable undertaking.

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