December 26, 2019

A Dry Year With a Twist and Few Major Fires

2019 was generally a drier than normal year.   But there were few fires during the summer and little smoke in western Washington and Oregon.  How can that be?  And agriculture was generally fine.

So let's talk about this year's precipitation, which we can do since there is only a few days left of the year.

There will be some rain the next few days, but nothing serious over Washington (see the prediction for accumulated precipitation for the rest of the month).  Around a half-inch over the lowlands, a few inches in the mountains.     In fact, with general westerly flow, Puget Sound will be substantially rainshadowed by the Olympics. Much more over coastal British Columbia.



But let's look backwards to the beginning of the year.  As shown by the map below, California, Nevada, and southeast Oregon have been very wet, but western WA has been quite dry, much of it with 70-90% of normal.  Not the end of the world, but less than normal.  The moisture over California played a big role in keeping the fires down and ensuring plenty of water there.


However, the annual precipitation total does not tell the whole story.  Below is a plot of the accumulated observed (purple) and normal (cyan)  precipitation for this year at SeaTac. 

The year started near normal, but we fell behind in spring, but slowly caught up during summer...that will be important. A wet September almost brought SeaTac to normal.  Then we had a very dry October/November and Seattle fell to 10-12 inches behind.  But fortunately, the big rain of last week got us to a few inches below normal.   An meteorological roller coaster ride!
In contrast, Quillayute, on the WA coast, was not only drier than normal, but did not get the big atmospheric river rain experienced by Puget Sound and SW Washington.  Shows how narrow the atmospheric river was.   They are a good ten inches below normal right now.   But really no serious implications of this....they still received 70 plus inches.
Yakima, on the eastern side of the Cascades, ended up wetter than normal, thanks to a very, very wet February/March
So why few fires this summer, while 2018 had things ablaze.  Particularly since the overall rainfall here in Puget Sound was nearly the same during both years.  One explanation: precipitation were very different during the summer between the two years.  To show this, here are plots of the daily precipitation for 2019 and 2018.   For 2019, we had frequent light amounts throughout the summer.  Keep things cool and relatively moist.

In contrast, 2018 had long summer period without rain.  THAT made a huge difference. The smoky year or 2017?  A year that had much more precipitation.  2017 had a very extended dry period during the summer (see below)
So the natural question you might ask, are our summers getting drier or were the last few years just random excursions?  Below is a plot of July/August rainfall totals over Puget Sound for 1900-2019--a good measure of what is coming into the region (this is the NOAA climate division precipitation for WA Division 3).

2017 and 2018 had very low summer totals, and  you can see the rebound in 2019.  In fact, 2017 was the lowest since 1930!  Is there a long-term trend.  Really hard to say.  Not much over the entire period, but a drying trend over the past 40 years.

What would we expect under global warming? 

Well, I am in a position to give you some new information on this.  We have run high-resolution regional climate models for 130 years (1970 to 2100. And we did this for an ensemble of many (12) global climate models.  The results, shown below for Seattle for a VERY aggressive increase in CO2 (we go crazy with coal!), indicates a very, very slow downward trend of summer precipitation.

My conclusion:  low precipitation for 2017/2018 was probably just random chance--good news for our future summers the next few decades.

15 comments:

  1. Cliff
    Last summer was much damper than the previous 2. We do hay for our cows and had to get it out of the field right after baling because the next day it would rain. A tough hay year.

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  2. Forest moisture is also influenced by the actual air temperature during the summer. Is there a trend in that regard? If we were to project a trend in forest fires, we'd have to look at both, as well as forest density.

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  3. What continually amazes is that the US Drought Monitor has consistently displayed severe decreases in total precipitation for the past year, even with the large amount of rain we just had here in Portland. As per usual, methinks a political agenda is at play here.

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    1. Ditto. No real "drought" hardship ever occured here in respect to vegetation, habitat, or water supply, and yet it glares "as if" on the maps.

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    2. You can go ahead and add all of the days precip together on your own if you think there's some sort of government conspiracy going on.

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    3. Thanks, I did just that - I came up with a few inches short of average precipitation for the year. So why the huge discrepancy? Don't be shy now, you asked for this.

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    4. We've been through this countless times here. Eric Blair is right. See Cliff's posts on it 11/21/15, 12/21/15, and 2/21/16 for a sampling back in the "wet drought" days when it was over the top ridiculous. Thank you Cliff for being one of the few who consistently calls out the fear-mongering on drought. We need more voices speaking truth, not less.

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  4. Good post, and timely. Looking back at the year’s weather is always a hot topic as December 31 draws near. Water-watchers compare data on a rain-year basis (Oct-Sept). Many people “sum” data on a calendar basis, and those don’t align well. Of course long term observations do level out “in the wash,” so to speak. I’m lucky to live in a place with weather data that stretches back to about 1895.

    Location definitely makes a difference in respect to what qualifies as a "wet or dry" year (or season) within the range-of-normal over time.

    When I recorded this morning's weather data, out of sheer curiosity I looked-back at my CoCoRaHS December precipitation figures for the last couple of years. Here, in Dec 2017 we had 7.81” precipitation (rain and snow), Dec 2018 was 10.21”. As of today, we’ve had 8.72”. The rain-year that ended on September 30 caught-up to the PRISM average. Depending on where one starts-and-ends timeframes, I have a hard time seeing this year as "dry". The daily and seasonal averages seem to have been more adrift than extreme.

    This year, 2019, we really did have a wetter-than-normal summer. My spreadsheets are set-up for 51-day rows-block only to optimize Excel pagination. Without reading anything into the timeframes, I do know that precipitation here from Sept 16th to Nov 5th averaged .20” per day (one inch every five days for the math-challenged); and .24" per day from Nov 6th through today, almost a quarter-inch per day - and the month isn’t over. We've had standing water for long stretches (unconfined aquifer) through 2019. I would hesitate to call the Pacific Northwest "dry" though I know the banana belt has had a rough go.

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    1. Location...I averaged 5" a day over two days...SW Washington. 1200'. Two story partly below grade basement. About an inch of it ended up covering about half my 2000 sq basement slab. (I guess the Nisqually quake breached my foundation seal) Just about got it all dried out. Good thing it's just rain water with some pine needles under the carpet. Smells fresh and clean! Merry Christmas!

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  5. Thanks Cliff for the analysis. It would be interesting to analyze whether and how this year's weather patterns were related to the El Niño/neutral conditions we have had in 2018-2019.

    I am also interested in knowing whether there is really an increase in the probability that we may experience La Niña conditions in 2020. According to the following website, the probability of La Niña will increase to 22% by fall of 2020 from the current 0% (while neutral will be 51% and El Niño 27%):

    https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=enso-cpc_plume

    If you have any insight how to interpret these numbers it would be great if you could please share it.

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  6. That is good news, Cliff! My favorite blogs are those that include historical fact projections to what we can expect with climate change. It helps people become less emotional about the future. They are better able to imagine solutions for adaptations to climate change issues rather than living in a generalized state of fear.

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  7. Just thought I'd point out how the current (12/27/19) 8-14 day outlook (for 1/4--1/10/20), for what is essentially the coldest (and relatively moist) time of the year on average, is looking interesting: https://www.cpc.ncep.noaa.gov/products/predictions/814day/.

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  8. Any chance you will start showing probability error bars, not just averages on data? That would sure allow more informed grounds for comparing trends or even year on year comparisons.

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  9. Cliff,On a previous blog concerning global climate change you mentioned "reasonable" sale of water rights as somehow correlating with climate change action.

    I was curious what do you mean by "reasonable" and how selling water rights mitigates climate change?

    This is a topic of concern for rural and farming communities as many don't want to see water, a public resource, being sold and controlled by the highest bidder.

    Also in that same blog you seem to want to control where people choose to live by cutting off Emergency Services to homes at risk from wildfire.

    If a teenager is in a car accident due to cell phone usage, would you still grant them Emergency Services?

    Or how about people living in the shadow of Mount Rainier or near an earthquake fault, no emergency services?

    Chris H.
    Heli-free North Cascades

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  10. Signs of snow on the horizon? Like next 7-10 days, how accurate is that? I've been watching for the past couple of days now and its varied a bit but mostly still sticking to a marginal chance for snow late next week. Any thoughts? Thanks Cliff!

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