August 25, 2020

California Wildfires and the Lightning Siege: How Unusual Is It?

California is burning and smoke has covered the northern half of the state and is spreading across the U.S.  
Most of the fires were started by a huge "lightning siege" that started on August 15th.  How unusual was this massive lightning event?  That question will be answered below.
Smoke situation this morning
The situation this morning was extraordinary.  According to CALFire, more than 14,000 firefighters are dealing with 650 fires (two dozen major ones) that have burned over 1.25 million acres.  There have been 7 fire-related deaths and 1400 structures lost.
The "lightning siege" over the past ten days has resulted in over 13,000 lightning strikes, many of which were from high-based thunderstorms that did not provide much rain to the surface (rain evaporated on the way down!).
How unusual was this large number of lightning strikes in mid-August?
The answer:  very unusual.
When I want to get information about lightning statistics, I know where to go: Professor Robert Holzworth of UW ESS and Dr. Katrina Virts, a past associate of Dr. Holzworth who is now a NASA scientist.  Dr. Holzworth runs a major lightning network (WWLLN) and a lightning expert, and Dr. Virts is the Mozart of lightning statistics.
Anyway, within of hours of inquiring about the situation, Dr. Virts sent me a graph showing 3-day lightning totals going back to late 2009 (below, click to enlarge).
The event that occurred last week was the sixth highest for that period, which is impressive by itself.  
But there is more.  It was the greatest 3-day lightning total in the entire period during the midsummer (June-August) period.   So this was quite an extreme event to occur in the warm/dry California summer.  One that followed an extreme warm period with a record-breaking upper-level ridge of high pressure centered over southern Nevada.
An important aspect of the unusual event was the ability to tap the moisture of tropical storm and move it into central California (producing the thunderstorms).  This is illustrated by the map below, which shows moisture around 10,000 ft (700 hPa pressure level) for 5 AM on August 17th.  The moisture levels getting into California were as much as 4-5 standard deviations from the normal.  Trust me...this is very, very unusual.  Like never happening before on that date.

Sometimes the atmosphere rolls the meteorological dice and gets two sixes.  
And, of course, the slow warming of the atmosphere from increasing greenhouse gases, the spread of invasive, flammable grasses, and the huge influx of people into rural areas make things that much worse.
On the other hand, there is very little smoke over Washington State and things look favorable over the next week.  I am becoming increasingly confident that Washington is going to dodge the wildfire bullet this summer.
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My blog on the KNKX firing is found here.
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5 comments:

  1. Eastern Washington has been fortunate so far this summer in having almost no lightning, especially along the lower Cascade east slopes where it has been very dry. Wenatchee has had the least amount of rain for the period from February 1st to the present as any year since 1973 and no measurable rain since June 12th. The recent heat and dryness since the last part of July has significantly dried out the fuels. If we had had a lightning outbreak such as northern California had, we would likely have had many large fires. This lack of lightning this summer I believe is the main reason for the low number of large fires this season.

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  2. Growing up in the PNW and spending a lot of time in CA, I do not remember that we had so many monsoonal moisture events with associated thunderstorms. Perhaps that is because I was mostly in Seattle and I am now in the Columbia River Gorge where we seem to have a lot of thunderstorms every year now. But I also notice a lot of tropical storm activity every year in Baja Sur area which then tends to affect the western US as the storms degrade. Cliff, is increased monsoonal moisture over the pacific coast states predicted by global warming climate models?

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  3. "And of course, the slow warming of the atmosphere from increasing greenhouse gases...."

    Com'on Cliff, you know that's all a load of bollocks. Don't keep adding in "greenhouse" garbage into your postings just to appease the howling mob.

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  4. Greenhouse warming is an assumption based on lab experiments dating back to the 1800s. It is a reasonable assumption. A coming climate crisis is not a reasonable assumption.

    The lab experiments suggest mild harmless warming and that is what we have had.
    Whether the warming is from natural causes or man made is an assumption tht can not be proven. I don't care which -- I like warming here in Michigan USA.
    Mr Mass may have lost his job but this blog is better than ever, and it was already very good. Leftists must have been reading every word here for years before they could get him. For a real scientist, who should ALWAYS be skeptical, being attacked by leftists is proof that you are accurate and an effective communicator.

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  5. Having spent the last 60 years in the coastal areas of western Washington, it becomes obvious to the free thinker for the main reason we have had such aggressive fire sessions in the recent years. Forest management has changed drastically. We used to clean up debris. Now, as part of being green, we let it lay there and dry out, becoming a massive fuel pile. True, that is how nature cleans up, but we ought not to blame it on climate change.

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