A dense smoke plume from large wildfires in Alberta has reached the Pacific Northwest.
The view from the Seattle PanoCam, looking northwest around 7 AM this morning, clearly shows the southern edge of the smoke cloud.
And the visible satellite imagery around the same time displays the massive smoke cloud extending southward over Washington State. You can also see low clouds over the Pacific, which extended inland into southwest Washington.
As the smoke cloud moved in, visibility around Seattle has declined and the Cascades are now in the haze.
Why is our air quality decent, with lots of smoke in the vicinity?
Because the smoke is overhead and not mixing down to the surface!
To demonstrate this, below are plots of ceilometer data from a unit in Marysville, WA deployed by Puget Sound Clean Air Agency. Ceilometers shoot lasers vertically and can measure the amount of smoke overhead.
Time is on the x-axis and increases to the right. You can see the dark area between 2500 and 4500 meters above the surface. That is the smoke. This is high enough that there is a good chance it won't mix down to near sea level.
A classic situation. Distant wildfires produce smoke that can move in overhead but are too high to be mixed to the surface as the ground warms and the lower layers of the atmosphere convect (moving up and down from surface heating).
So why did we get a shot of the Alberta smoke? Because the lower atmosphere winds were just right!
Below are the winds at around 5000 ft (850 hPa pressure). Winds from the north over Alberta and eastern BC, become northeasterly (from the NE) over Washington State. Perfect for moving Alberta smoke into the Northwest.
Why the smoke now?
There is a lot of talk about the smoke situation, with some suggesting that global warming is the cause.
To understand the situation, consider that late spring is NOT an unusual time for large wildfires in northern Alberta. For example, there was the May 1, 2016, Fort McMurray wildfire and the Flat Top Fire during May 11-15, 2011. And there are many other examples I could cite of major Alberta fires in spring.
Importantly, the fires were set up by REGIONAL warm/dry conditions associated with anomalous high pressure over Canada this spring.
Let me demonstrate this to you. Below is the difference from normal of heights (like pressure) at 500 hPa pressure (about 5500 meters above sea level for March 15 to May 15. Do you see the yellow to reds over southern Canada? That is higher than normal heights and pressure, which results in warm/dry conditions.
The ridging/high pressure set up the fire. Also note that the anomalous upper-level pattern was associated with troughing (lower than normal pressure) over the West Coast, giving us a wet/cool pattern--particularly in Californian).
So the wet conditions along the West Coast and dry/warm conditions in Canada can be traced to the SAME anomalous upper-level pattern.
I have an old friend who just retired from the US Forest Service. He has been fighting forest fires forever, it seems. He just mentioned that firefighters have to have safety supervisors (for obvious reasons) but that there are very few remaining and it is difficult to obtain the level of knowledge to be promoted into that position. So, Canada is asking for US Forest Service support for these current fires. And, well, for today there are no available safety supervisors, thus no additional firefighting teams available to fight these fires at the moment. And this is a serious situation. With no immediate solution. And we would need newly interested folks to step up to the plate for future promotion into safety positions. Not sure how one goes about doing that. One could imagine the future, should this issue not turn itself around.
ReplyDeleteMuggy, smoky day around Bellingham with dew points in the mid-60s on 5/16
ReplyDeleteJust north of BLI it was sunny and warm mid 70's, worked outside for 4 hours planting flowers and playing with the dogs. Didn't seem humid or smoky during afternoon/evening.
DeleteTerrible news indeed. I do see rains on the horizon. Sunday perhaps
ReplyDeleteThank you SO much for sharing the profile-elevation image. A lot of people don't visualize the atmosphere in 3D terms, but I consider that dimension as essential (the whole ball of wax, so to speak). Ground observation(s) are just one reference point in the big scheme of things. I often gaze up, wondering what's going on overhead as I see distinct layers of clouds zipping this way and that, vortices, currents etc. - cumulus and thunderheads seeming to build, then dissipating. The smoke layer -- glad it's high. It's hazy here (Thursday morning), and that's filtering some of the sunlight (nice).
ReplyDeleteHigh altitude or not, smoke is just ugly. I like the azure blue sky that used to dominate every clear day nearly all summer.
ReplyDelete