During warm days there is a profound change in winds up and down the Olympics that is normally invisible, but become apparent when there is a wildfire on the Olympic slopes.
Dale Ireland has a wonderful permanent cam facing the Olympics and has been recording the smoke from the Big Hump fire the last few days.
Here is a video for a few days ago: http://www.drdale.com/lapse/lapse110906s.mov
This one is also good: http://www.drdale.com/lapse/lapse110903s.mov
During the day, as the slopes are heated there is upslope flow moving towards higher elevations--this upslope flow and the destabilization of the atmosphere as the mountains heat up produces convection and enhanced upward flow. Sometimes this convection is accompanied by a cumulus cloud as well as smoke (called pyrocumulus). The rising air cools due to the expansion of the upward-moving air and eventually the initially warm air is no longer buoyant (becomes the same temperature as the environmental air at that level) and no longer rises. You see this all the time from smoke from smokestacks hitting a level through which it can pass and then spreads mainly horizontally--check out this picture:
During the evening, the surface of the mountains cools as the infrared radiation loss to space exceeds the incoming energy from the sun. The daytime convective/smoke plume dies (since it depends on the surface being sufficiently warmer than the air above), and air starts moving down the mountain....known as downslope flow. The smoke is entrained in this flow and heads down the slope. That is what you are seeing.
Thanks for the explanation. Now I can understand more about what I am seeing. I enjoy your excellent blog.
ReplyDeletewho cares about weather esoterica, i hope you find your dog
ReplyDeleteWhat is the sudden burst of smoke right at the end that goes straight up? Did I miss the point? In the first part, I see the hazy smoke gradually slipping down the slope as you describe.
ReplyDeleteI see the hazy clouds slipping down the slope gradually in the first part, but don't understand what the sudden plume that goes straight up near the end is about.
ReplyDeleteThank you
From our home in Magnolia we saw the fire's smoke rise up as you described, but then drift off to the north.
ReplyDeleteAt that same time, down on the Sound and at our home, the prevailing wind was out of the north.
Please explain the different wind directions.
John M
there is no such like that around my house,,, what i see only green forests
ReplyDeletethanks for giving the information
Two thoughts.
ReplyDeleteFirst 'Records' are generally meaningless. Is there any climatological significance to the consecutive days above 80 in September? What if a string of above 80 started on the 20 Aug and continued until 9 Sept. Or, if the string started with 7 days in the upper 80's and then had an weak onshore flow where the temp dropped to 79 for a day and then had another string of 8 days above 80. Or does a string 8 days above 80 at the end of the month have more weight 10 days at the start of the month? And that has been pointed out by Cliff in earlier blogs, the variation around the region be dramatically different. I would suggest that all 'Records' should be either marked with an asterisk or ignored. These should not be considered journalistic news and left to grocery store tabloids.
Second, while I agree with the statement that 'not all site locations are created equal', I do wonder if we are trying to equate apples to oranges. I understand location of the sensors at Sea-Tac have been influenced by the third runway. But I also wonder that if a group of sensors was put over natural vegetation in downtown Seattle, would that be at Freeway Park? and would that reflect the conditions within micro climate created by the concrete and asphalt of downtown Seattle. I would suggest that this is a problem of resolution. The finer we calibrate the instruments and area of reference, the more samples need to be taken.
Still after 45 years ago, the words of my Ingraham HS Chem teacher, Wendell McCain, still reverberate in my mind - the Law of Significant Digits. And related. One can not be more accurate than the least accurate measurement. And that measurement errors accumulate. Unfortunately, we live in a world of floating decimals of computers/calculators and assume our measurements are accurate to 8 places.
Let's keep a perspective on these observations and realize they only indicate trends subject to variation and not 'Records'.
I hike a lot in the Cascades, and I often get a chance to survey the various mountains from a high vantage point. Recently, on two occasions, I noticed that it was very smokey by Glacier Peak. The first time I assumed there was a new fire there. After checking the fire report (inciweb) I'm now assuming that all of the smoke is from the fires in the Olympics. I think the smoke from those fires moves over the convergent zone, where it obscures Glacier Peak. This was visible on a couple of occasions, from both the north and the south.
ReplyDelete