As expected, the massive lightning event this week led to the ignition of several wildfires.
But our region lucked out: few fires were started on the eastern slopes of the Cascades within forested areas.
This is because we are in the early season, which means less time for drying in the slow-to-dry forested areas, and because of the distribution of lightning (relatively little lightning on the eastern slopes).
Below is a map of the largest fires.
Most were in grass and range vegetation, with the greatest fire activity in southeast Washington and northeast Oregon, where the most lightning occurred.
You can see the smoke in the midday high-resolution visible satellite image (as well as low marine clouds over western Washington).
Some satellites can observe the heat from the fires....and here is the same image with fire locations (orange dots).
The grass/rangeland of northeast Oregon is clearly the "hot spot" for the fires.
It is important to note that such fires have little to do with global warming or heat waves.
Light fuels, such as grass and range vegetation, are typically dried by now, and lightning events like this week have no correlation with a warming planet.
Below is the data from the US Forest Service showing you the 100-hour fuel moisture levels. (100-hour fuels include dead organic materials, such as branches and dead roundwood, that measure between 1 and 3 inches in diameter.) The observed moisture levels (red line) are in the middle of the average range (gray shading).
But something has changed over the past decades the was made our grass/rangelends far more flammable...the invasion of explosive-burning cheatgrass and other fire-friendly species.
This map shows you the extent of the problem and why eastern Washington and Oregon are so vulnerable
Flammable grasses have taken over the region (see below), and ignition by lightning or human activities can start a firestorm.
And there is one more thing.
To get large fire growth requires strong winds, and the weather systems that produced the thunderstorms also provided large wind gusts, both during the storms and after.
Want proof? Check out the maximum winds on Thursday (below).
Winds are declining now, and you can expect that the grass/range fires will quickly decline.
" cheatgrass and other ..."
ReplyDeleteThere are a half-dozen or more highly burnable grasses including Red brome, Lehmann's lovegrass, Buffelgrass, Mediterranean grass, Medusahead, and Ventenata. Which ones are in WA State and where is not something I know. My property has the common Cheatgrass [Bromus tectorum]. It is common in Kittitas and Grant Counties -- just follow I-90 into central WA.