Lightning and Fire

As if the fire situation were not threatening enough already, lightning activity ramped up over the weekend across interior Alaska.  There were nearly 30,000 lightning strikes from Saturday through Tuesday, which is more than some years see in all of July.

However, compared to some of the big lightning episodes of recent years, the last few days have not been too unusual.  For instance, the peak 2-day strike count of around 17,000 strikes is about normal for the maximum observed in recent summers, based on data since 2012.  Several years have seen much greater 2-day outbreaks: over 50,000 strikes in mid-July 2016, over 40,000 in late June 2015, and 36,000 in July 2019.

It's interesting to consider whether wildfire acreage tends to increase more rapidly after large bursts of lightning activity.  This is a question that could be assessed in many ways, but for a quick look I examined the fire acreage within 30 days before and after each summer's peak 2-day lightning strike count.

Note that I excluded 2014, 2020, and 2021, which had relatively subdued lightning peaks (on the order of 10,000 strikes), whereas all the other years on the chart had peaks at least as great as last weekend.  The order of the years in the legend at right shows the order of peak 2-day strikes from greatest to least.

It's somewhat sobering to see that all but one of the years saw more acreage burned in the 30 days after the lightning peak than in the 30 days before, although of course the magnitude of acreage differed vastly between years.  A couple of years - 2015 and 2016 - saw a pretty obvious acceleration in fire in the week after the lightning peak, but in other years there isn't a clear connection.  No doubt a more in-depth analysis would provide additional insight.

While the recent lightning is certainly not good news, the medium-range weather outlooks from the Climate Prediction Center have been trending in the right direction lately.  Here's the latest version: this is distinctly encouraging.