Wildfire Forecast for the Summer

Several people have asked me about the threat of wildfires for our region this summer.    

I have good news for them:  the wet/cool spring and other factors make a major wildfire season in Washington State highly unlikely.  That means less low-level smoke and other impacts.

Why are folks so nervous?   A major stimulus has been irresponsible media, such as the Seattle Times.

For example, Seattle Times cartoonist David Horsey published a recent cartoon showing Washington State on fire, with flames and smoke extending over the entire state (see my rendition of his cartoon below).

And ST's David Horsey doesn't stop there in inducing fear:

"That means another summer of wildfires. And that means smoke....there’s a good chance of that perfect August weather in Western Washington being smothered in an acrid cover of smoke blowing in from fires to the north, the east and the south."

As I will describe below, David Horsey and similar fearsters are ignoring science and data.

So let me explain why wildfires will be restrained this summer in our region.

Reason 1: An abnormally large snowpack.

    We are talking over 150% of normal! (see below).  As a result, the middle and upper slopes will melt out later than normal and the "fuels" will stay moist well into the summer, which delays the onset of wildfire season in the mountains.

Reason 2:  A cold, wet spring

This is important.  This year is a lot like 2011, whose summer had minimal local fire activity. 

To understand the situation, check the plot below of the number of acres burned each year over Washington State during the past two decades. 

There were more fires during the past decade than previously, which won't surprise any of you.  But look carefully.  There was one standout year for lots of fires (2015) and another with almost none:  2011.   The forests were not that different between the years--so what explains the huge variation?  

Below is a plot of the average temperatures in April and May for Washington State. 2011, the year with the least fires, had the coldest temperatures by far!  In contrast, 2015 was one of the warmest years.

What about spring (April-May) precipitation?    2011 had the wettest spring during the period, while 2015 was very, very dry.

It all makes sense.  A cool, wet spring leads to fewer fires and a warm, dry spring leads to more fires.   Importantly, in both years,  springtime conditions continued into the summer.

So what kind of spring have we had this year?   

Extremely cool and wet like in 2011. Of course, May is not finished yet, but if we look at the last 60 days, the State has been hugely cooler than normal, particularly the fire-prone eastern part (see below).

Consider Wenatchee on the eastern side of the Cascades and near the eastern Washington fire area. For the period April 1-May 23, Wenatchee "enjoyed" the wettest year since 2011 (see below)

And Wenatchee has been COLDER this year than in 2011.

Seattle had the coldest year since 2011 (see below)

Take home message:  spring temperature/precipitation is correlated with summer wildfire area over the state, and this spring has brought very similar conditions (cool/wet) as experienced in 2011, whose summer had minimal wildfires.

Reason 3:  The extended model forecast indicates a cooler than normal June and normal precipitation.

The latest European Center extended forecast predicts a cooler than normal period through the end of June (see below, blue and green colors indicate below normal)

The total precipitation forecast for the next month (below) is very normal overall (and slightly wetter than normal over western Washington).  As an aside, the upcoming Memorial Day Weekend will be moist, with particularly heavy amounts in Oregon, where it is needed.

Obviously, a cool, moist June delays the fire season.

Reason 4:  A Strong La Nina Summer

There is a substantial impact of El Nino (warm tropical waters in the central/eastern Pacific) and La Nina (cool tropical waters) on the eastern Pacific sea surface temperatures and weather over our region.  And a significant wildfire influence as well.

The figure below shows the key index defining La Nina/El Nino for each three-month period since 2010.  This is the Nino3.4 index, with large negative values (-.5 and less--blue colors) associated with La Nina and larger positive values (+.5 or more-red colors) with El Nino. Based on the latest observations and model predictions, I have put in the expected value for this summer.

Note that the big fire year (2015) was associated with a strong El Nino and the low wildfire year (2011) with La Nina.  This makes sense: we tend to have cool, wet springs during La Nina years, with cool conditions extended into the summer.

This summer will have a La Nina as strong or stronger than 2011!

La Nina years are associated with cooler than normal northeast Pacific waters and that is exactly what is going on now (see sea surface temperature anomalies...difference from normal.  You see all the cold (blue) waters off our shore?

Since air moves eastward from the Pacific into our region, this implies a cooling effect for this summer.

Reason 5:   Much of the Vulnerable Forests in Our Region Have Already Burned

We have had a lot of fires during the past decade, as the poor forest management of the past century has caught up to us.  By suppressing fire and allowing a dense, unhealthy forest to develop, we created a tinderbox in which large, catastrophic fires have occurred.

There is substantial scientific literature demonstrating that the passage of fire through a region suppresses future fires for a decade or so.    Thus, with so much burned during the past decade, there are fewer fuels available today.   This is a fact that few in the media have talked about:  fire makes more fire LESS likely in the short term.

To illustrate the situation, take a look at the burned area of north-central Washington from 1985 through 2020, as shown by a graphic from the marvelous wildfire explorer website (thank you to Dr. Susan Pritchard for pointing this out to me).  The colors indicate burn severity.

A huge proportion of the area has already burned and is thus LESS likely to burn today.

Reason 5:  The Fuels are Unusually Moist

Fires need "fuels", such as dried grass, downed trees or slash, and the like.  Moist fuels prevent or restrain fires.  And because of our wet, cool spring, the fuels in nearby forest are unusually moisture-bound.  

Consider the 1000-hr dead fuels (branches and the like of 3-8 inch diameter) for the critical eastern slopes of the Cascades and the Okanogan region to the north.  When we get smoke in Seattle, the fires are generally in this region.   

The graphics below are from the Northwest Fire Coordination Center.  The red values are observed fuel moisture levels, and the central line surrounded by gray are the average values.  The top and bottom lines are observed extreme values and the gray area includes observations within two-thirds of the mean moisture. 

Region 6 encompasses the Washington Cascades' eastern slopes and region 8 is the Okanogan area.  Wow.   The moisture content in both areas is well above normal...nearly a record high.  This stuff is not going to burn very soon!

California smoke?

The situation in California is very different from that in the Northwest.  They have been much drier than normal this past winter and thus CA fuels are primed to burn early.   There will be significant fires over the Golden State this summer, with the only good news being that the dry winter/spring will result in less flammable grass.

California fires rarely produce lowland smoke over Washington State, since any smoke that reaches us tends to stay high.   We may have some haze, but little air quality impact occurs near the surface.

To get lowland smoke over Washington the fires need to be close:  either over Washington or the adjacent areas of BC or Oregon. 

California Smoke Moving Northward in 2018

In summary

Actual data and historical wildfire information suggest a very benign local fire season in and near Washington State.  Could we have a big fire if the meteorological conditions come together later this summer?  Yes.  But it is clear that the meteorological situation is not favorable for wildfire.

If things work out as the data suggests, I hope Mr. Horsey and the Seattle Times will consider the following idea for a cartoon later this summer when the smoky future they predicted does not materialize.