The weather changed about two weeks ago from warm and sunny to warm and wet. Well, of course it has cooled off - enough so that I have broken out the winter blankets - but it is still pretty warm. T-shirt weather for me when I go let the goats out to graze. I'm still drinking my coffee iced; I haven't switched to Americanos yet. There has of yet been no sign of a frost.
Two weeks of rain has turned the barnyard into poo-soup, and when I go out to do the chores in the morning I definitely have to put on galoshes. The dog comes with me, and is banished from the house until her paws dry off. The sky has been low, grey, and glowering, which has an effect on my mood. It hasn't been very pleasant, weather-wise, but neither has it been cold. Today, a friend posted a link to a weather blogon her Facebook page, and it was very enlightening. So far, Pacific Northwest Weather this year HAS been unseasonably warm - record-breakingly warm, in fact. But the record - highest average low temperatures - is not one that people generally pay much attention to. The following is chart heavy, but I found it very interesting.
A note: as much I am unsettled by weird weather, tending to real out and imagine catastrophic climate change on a human time scale, I am nonetheless grateful for this year's odd warmth. We will not be able to use our furnace until all the work is done in the crawlspace. and that isn't projected to be completed until mid-November. So as far as I'm concerned, let the frost stay wherever it is now!
Reposting from Cliff Mass Weather Blog (link below)
****UPDATE****** I don't know why the cut-and-paste job below is cut off on the right margin. I can't seem to adjust it in my editing platform. However, if you click on any of the graphics, they will show up whole and legible in a new window.
Here are the temperatures at Seattle-Tacoma Airport during the past 4 weeks, with the average high (red) and lows (blue) shown. Only ONE day in that entire period has seen the temperature dropping to the average low. For most days, our minimum temperatures have been 5-10 degrees above normal. Our minimum temperatures last night were close to the average maximum for the date!
And this is not Seattle alone, here is the same trace for Bellingham. Same thing. Bellingham cooled to 59F last night!
Now why is this happening? This is an important question because one can expect some folks in the media and advocacy groups to start saying this is a "sign" or "consistent with" global warming due to mankind's emissions of greenhouse gases. There is no reason to think that is true.
There are two main reasons for the warmth and they are both associated with the anomalous atmospheric circulations we are having.
Reason #1: a persistent area of low pressure over the eastern Pacific. The figure below shows the sea level pressure anomaly (difference from normal) for the past month. There is an area west of us with pressures well below normal. Such anomalous low pressure is associated with stronger than normal southerly and southwesterly winds over us that blow in warmer than normal air.
This is probably the major cause. Then there is something else, something I have talked about in previous blog: the warm water BLOB off the coast.
Below is the sea surface temperature anomaly map for the past week. You see the orange and red colors off the coast that indicate temperatures 2-4F above normal? The BLOB still lives. So air passing over the eastern Pacific is exposed to warmer than normal water. Me like BLOB, BLOB is good.
As I noted earlier, the BLOB has little to do with global warming but was produced by anomalous high pressure over the Pacific last winter and year.
So our ridiculously warm temperatures this fall are being produced by an unusual combination of high pressure a year ago that produced the blob and low pressure this fall that is bringing up warm air from the south.
There is no reason to think that these circulation anomalies are caused by human greenhouse gas emissions. And remember that the eastern U.S. has been colder than normal.
Well, time for me to go out to my garden to harvest some more red tomatoes.