Drought Misinformation

There have been a number of stories in the press and on the web about water issues this summer in the Northwest; some are reasonable but a disturbing number are exaggerating and distorting the situation, predicting a catastrophic wildfire season and billions of dollars in crop loses.  And some folks in the political arena are playing a bit lose with the facts as well.

You want some examples?  Crosscut calls out a SUPERDROUGHT.

This over-the-top piece does not stop with this year:

"The 2015 superdrought will likely be a harrowing experience for many state citizens, and could be followed by another, similarly terrible year.'

 Others talk about a TINDERBOMB due to low snowpack

Or in the Oregonian:

Will there be a superdrought this summer over the Pacific Northwest?   Will low snowpack bring huge wildfires?  Let's get beyond the hype and look at data and forecasts.

First, let's be clear.  There is no drought over the Pacific Northwest and by that I mean no precipitation drought.  For the last six months, here is the % of normal precipitation over the western U.S.  Most of Washington State and the eastern half of Oregon received 90-110% of normal.  The rest was at least 70%.   California and Nevada is a different story, with real drought.   You can see why William Shatner wants our water.

What about conditions on the ground?  One of the most considered measures of drought is the Palmer Drought Severity Index.   Here are the latest values.  Most of Washington State is near normal and eastern Oregon is wetter than normal!

What about the the NOAA crop moisture index?  Normal.

And the last two weeks have been unusually wet  (green and blue) over the eastern side of the Cascades.

And this evening's WRF precipitation forecast for the next 72h looks like something that would inspire Noah to start building his ark:

While the latest forecast of total rain over the next 9 days from the National Weather Service's GFS model would bring happiness to any Northwest duck.

And keep in mind that Columbia River flows, draining off the higher terrain of British Columbia, which had a better snowpack AND more precipitation, will only be slightly below normal.   Plenty of water for hydropower, irrigation from the Columbia, and fish in the river.  And because of substantial reservoirs and wise stewardship, nearly all of the populated areas of the region will have sufficient water.

So this talk about the Northwest being in a drought, super or not, is really problematic.    We have had near normal precipitation, our soil moisture is near normal, our reservoirs are full, the Columbia is near normal, and the drier parts of the state are being hit by wetter than normal conditions during late spring.    

We DO have a lack of snowpack because of the warm temperatures last winter that resulted in rain but little snow in the mountains.    So maybe it is ok to talk of a snow drought, but that is a bit confusing to some perhaps.  This snow drought will be problematic for fish on some rivers (e.g., draining the Olympics), but there is little we can do for them.  Nature is cruel sometime.

So how worried should we be about wild fires due to the low snowpack?   And what about other factors?

I have talked to my colleagues in the wildfire business and most of them feel the snowpack issue is overblown.   They tell me that the key determiner of whether there will be extensive fires in the summer are:

1. Whether we are much warmer than normal in July and August
2. Whether there are a lot of thunderstorms to initiate fires.
3. Whether we are much drier than normal in July and August

Regarding the last bullet, we are normally dry during our summer, but rain can moisten the "fuels" and lessen the fire risk.

There is good reason to suspect snowpack has only a small impact on wildfire frequency and intensity.  First, the differences in snowpack between good and bad years is pretty minimal by the time of the main fire season, which is roughly from mid-summer to early fall.   Second, differences in snowpack early in the season between good and bad years is mainly at higher elevations, while most of the significant fires, and certainly the ones the affect most people, are at low elevations.   To show this, here are the areas of the major fires of the past 15 years.  Most are on the lower slopes of terrain east of the Cascade crest or in relatively low (and snowfree) coastal mountains.

There are a few papers correlating lack of snowpack with increased wildfire threat (e.g., Westerling et al. 2006), but I believe they have a fatal flaw.   Their low snowpack years were also precipitation drought years, which is NOT TRUE of this year.

So if snowpack won't be a major issue, what about temperature, precipitation, and thunderstorms?

Our best guidance for the seasonal predictions is the NOAA Climate Forecast System (CFS) model.   For temperature, its forecasts have been clear and robust.   Warmer than normal (see below) over our region.   That would enhance wildfire risk.

 Precipitation is a different story.  Nearly normal over Washington, but a bit wetter over eastern Oregon.

Predicted soil moisture?  Generally, near normal except for eastern Oregon, where it would be wetter than normal.

But then there is the thunderstorm issue...and folks, THAT is the wildcard.  The enhanced precipitation over the Rockies suggests more thunderstorms over that region and perhaps into eastern Oregon.  Might those thunderstorms get to up and start fires?   On the other hand, the CFS model predicts enhanced ridging over our region, which would lessen thunderstorms.

The bottom line in all this, is that a more nuanced view of the current "snow drought" situation is called for and the prediction of more wildfires is no slam dunk.  Talk of superdroughts is really nonsense.  

There is certainly no reason to expect fewer than normal wildfires and the warm temperatures will modest increase wildfires potential.  But the lack of snowpack is a minor issue.   Much is riding on the frequency of thunderstorms, and there is considerable uncertainty how that will play out.

As I have said many times, this year has many of the characteristics of 2070, when global warming will be significant.  That is why the work of Governor Inslee and the Department of Ecology to take all possible steps to adapt to a low-snowpack year is appropriate and welcome.  We need to figure out how to deal with a lack of snowpack, while preserving our agriculture, drinking water, and as much as possible of natural fauna/flora (e.g., salmon).  But hyping and exaggerating the situation is not helpful.

And for those in western Washington...be prepared for thunderstorms later tomorrow and into the early morning hours of Friday.