Monday, May 13, 2019

A Wet Period Ahead for the U.S. West Coast

The first half of May has been generally dry and warm over the Pacific Northwest, but soon everything will change.

The second half of the month promises to be cool and wet in Washington and Oregon, with northern California swamped by highly unusual amounts of rain.   As we shall see, this wet period has highly positive implications for the upcoming wildfire/smoke season.

To give some perspective, below is the precipitation departure from normal for the past 60 days over the western U.S.   Much of the region has had above-normal or near-normal precipitation, with the big exception being western Washington, which has been drier than normal.  Importantly for wildfire concerns, southwestern Oregon and eastern Oregon have been moist and the area east of Cascade crest in Washington has been near normal. 

Much of coastal California has been on the dry side during the past two months, but that is following a very wet winter.  The concern for California is that abundant winter precipitation will lead to lots of grass growth, which will burn later in the summer as it inevitably dries out. 

The forecasts for the next two weeks for the West Coast are consistent and wet.  The UW WRF forecast for accumulated precipitation over the next week indicate amazingly wet conditions over northern CA, with 5-10 inches over the Sierra Nevada and northern CA mountains.  This is HUGE for late May.  Heavy precipitation extends northward across the Oregon Cascades and eastern Oregon, and western Washington gets 1-2 inches (normal total May rainfall at Seattle is a little under two inches).  Forget watering your lawn.


Turning to the vaunted European Center model totals for a similar period, one sees very similar amounts of accumulated precipitation.  Folks, this is really wet for Oregon and California.


Now, any good forecaster does not look at a single model prediction, but views an ensemble of many of them to understand the uncertainty of the forecast.    Here are the 51 forecasts of accumulated precipitation at Seattle from the European Model ensemble for the next ten days.  90% of the members are on the same page, with precipitation starting on late Tuesday and 1-3 inches by May 24th.
Even light rain in Yakima, on the eastern side of the Cascades.


So what are the implications of all this?   

First, the atmosphere is not locking up in a warm/dry pattern as it did in 2015.  Second, this is an unusually wet pattern for California/southern Oregon so late in the season, one that will top off their reservoirs and ensure that there will be plenty of water in the Golden State this year. 

It will also delay the wildfire season there.  Third, western Washington will get some needed precipitation, lessening the chances of any early grass fires and will help fill our reservoirs, which are actually not in bad shape anyway.  The wet period will also radically reduce local water usage, leaving more water in the reservoirs.

There is a lot of fear-inducing headlines in the media and among some politicians about a terrible fire season because of the recent dry period and the low snowpack at some sites in northern Washington.


These worries are not realistic.   The upcoming wet period, which has been forecast for days, should moisten up the whole area.  The eastern side of the state had plenty of precipitation during the past winter and streamflow/soil moisture is fine there. 

The snowpack in much of California, Oregon, and southern WA is fine.   And low percentages in parts of WA this time of the year can be very deceptive.  Let me demonstrate this.

Below are the values of snow water equivalent (SWE, amount of water in the snowpack) and precipitation accumulation of this year versus normal at Stevens Pass--a location with anomalous low snowpack (SWE) today.     Total precipitation (black--this year, gray--normal) is just a little below normal (that will change during the next week!). 

But what about snowpack (Red normal, blue this year)?  The snowpack peaked at about 75% of normal and will melt out around May 15th, rather than the normal June 1.   So the % of normal today is crazy low (maybe 5%), but clearly the situation is not that serious...just an early melt out from the warm temperatures of the past month.


The bottom line:  At this point, it is premature to predict an early or more severe fire season for our region.

24 comments:

  1. And everyone was all worried that our dry season had set in early... lol

    I've lived in the PNW my entire life. 40+ years now, and the long-established norm says we always get a nice week or two in May, but the clouds and rain inevitably come back in time for Portland's Rose Festival. None of this is abnormal, by any means.

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  2. Hey Cliff!

    What are your thoughts about the conditions in the North Cascades? Seattle City Light and North Cascade NP have effectively said ross lake will be way below pool and in drought conditions.

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  3. Across the country, trends indicate that flooding is becoming the new normal. On Wednesday of last week, the National Oceanic and Atmospheric Administration (NOAA) announced that the amount of U.S. land experiencing drought has dropped to its lowest levels in decades. That dive has come hand-in-hand with a major uptick in saturation — from May 2018 to April 2019, the country saw its wettest year on record.

    Approximately 36.2 inches of rain fell in the contiguous United States during that period, a 6-inch increase above average that has left drought impacting only around 2% of the country.

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  4. COLA says mostly going to north California.

    Wanna lay some odds?

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  5. And once again the - only - rational voice through all of this drought bs... the constant fear-mongering... with actual facts and data to back it up, is Cliff Mass.

    Why is that? Why is he the only one?

    Everyday, no matter what the weather, it seems someone is trying to create fear. What a beautiful spring, but not if you read the paper or watch the news. It is fear and negativity 24/7, with a strong dose of weather revisionist history tossed in to make it sound worse.

    We are way better than this. Thank you Cliff for putting the truth out there.

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  6. Thanks, Cliff
    I liked the Stevens Pass graph. Very instructive.
    Can’t wait for the rain!

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  7. We Did... said "...Seattle City Light and North Cascade NP have effectively said ross lake will be way below pool and in drought conditions."

    Can you please provide a link to that?

    According to SCL's own graphs tracking back to Oct. 1 (start of the water year) SCL is at 90% precip in their watershed ytd. I would like to see them (or you if you have the data) justify Ross Lake being "way below pool" on June 30 given that fact.

    One of the consistent secondary problems with the media running with over-hyped drought stories this time of year is that it provides cover for utilities to either charge surcharges or increase rates as the summer dries (which it does in the NW). See the 2001 SPU "drought" where their CEO admitted, after the summer was over, that it had been "hard to stand up with a straight face" because they knew the drought they had proclaimed was bs... but they "didn't think it was a good message" to tell the truth (Seattle Times, 9/30/2001). If I recall correctly, they jammed through one of the largest permanent increases in rates that year.

    Based on 90% of precip, I would think SCL would need to explain to ratepayers why a 10% shortfall in annual precip isn't automatically built into their annual water management models if what you are saying is true. Our water engineers know what they are doing - it is very hard to see how any kind of crisis is possible given their experience, and the amount of water in the SCL watershed this year.

    Graphs here - https://www.seattle.gov/light/ctracks.html

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  8. Every Spring we seem to go through these shenanigans, but the MSM is addicted to click bait and scare mongering, so notwithstanding the facts it will continue unabated.

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  9. Thought for Sunsnow12: I think the old adage for local/region news was "If it bleeds, it leads."

    Let's face it, bad news has always been a money maker. So the more bad news you can gin up, the more you make.

    The only really significant change, in my opinion, is the accelerated News cycle. As opposed to preparing news for a several times a day broadcast, it's now a race for headlines, with messages being push out as opposed to consumed at your leisure or on a schedule. That and playing to your primary audience, which in the case of Seattle, reads anything scary, unusual, bad or otherwise suggestive of the negative effects of climate change.

    Newspapers have to know their audience to stay afloat. That's their world. It doesn't have to be mine.

    Which is why blogs like Cliff's are so valuable given they provide perspective and reason and a little time for thought.






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  10. ".. if you read the paper or watch the news. It is fear and negativity 24/7".

    Life is too short to waste time on them. You have the final say - just press the switch and turn them off.

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  11. Max temp in NW Bellingham today: 58F; min temp: 44F.

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  12. Just found this re: Ross Lake: https://www.nps.gov/noca/planyourvisit/faqs-for-ross-lake-low-water-lake-levels-2019.htm and We Did, you are correct in what they are saying.

    "The unanticipated low reservoir level is due to lack of rainfall, a decline in snow pack, and the protection of chum salmon redds resulting in a drawdown by Seattle City Light."

    First of all, unanticipated is a real stretch since they have had the last 7 months to manage this. But lack of rainfall give me a break. 90% of precip is not remotely a "lack of rainfall". Decline in snowpack? Of course there is a decline in snowpack in the spring, that is why you have your reservoir height - throughout the winter - directly correlated to the SWE in the snowpack so that on June 30 you have a full reservoir. See 2015 for how that is done... when there was virtually zero snowpack but we had full reservoirs (and the water didn't all come in May).

    SCL is saying the same thing with even more excuses - https://powerlines.seattle.gov/2019/05/03/low-ross-lake-levels-projected-for-2019-summer-recreation-season/... how much of a disconnect is there between that and the graphs they have on their own website?

    There is something wrong here. I agree... Cliff, you want to weigh in on this since you are about the only source that is believable? Man this stuff makes me crazy, we watched with our own eyes the rain pound the N. Cascades last fall, just deluged. That water didn't just disappear.

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  13. National Park Service has cancelled reservations and access to Ross Lake for boating campers, effective immediately and for the foreseeable future, due to exceptionally low lake levels. Exposed shore presents hazards, and prevents access to pump out camp toilets. If we are okay on water, why is Ross Lake being drawn down so much so early?

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  14. really weird..... the environment Canada measure for Skagit range went from 51% of normal april 1 to 15% for May 1.

    Typo? Seems a bit off. April wasn't so hot. Meanwhile the Americans are calling the Skagit 71% of normal. Anyway, Skagit was and likely still is way low compared to the rest.

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  15. Eastern wa. Is drier then I have ever seen it. Every swamp is dry already, creeks are easily walked through very early in the season, they usually get ample late April to early may rains which did not happen this year. Being on the ground is only way to really see this. In addition coastal wa. Looks like July already. And with all the foliage out now anything less then half an inch barely can penetrate the over/understory. Gonna be a long summer without a true soaker

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  16. Cliff, you show the graphs and say there is no cause for worry and I believe you.

    But for comparison sake, can you show on those graphs at which point we should be worried?

    Say the last graph, at which date or % (or combination) would we be concerned with if we were below average accumulation and also had a very early melt-off?

    How close (or far) are we from being concerned?

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  17. Wow, just cracked 1/2" today in the hills NW of Longview. NWS forecast tenth-to-quarter but a few late-day showers were pretty substantial.

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  18. 0.12" precip in NW Bellingham today

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  19. Good job of keeping local fire prediction real!

    I'm glad Oregon and California will be very wet.

    Today's rain felt refreshing as it cleansed pollen out of the air and watered the plants. I love the sunshine, but like the occasional rain too.

    Please continue showing the European weather model images. I always find them interesting.

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  20. More analysis on Idaho weather and climate Cliff. Please, and Thank you!!

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  21. Wednesday morning and I am looking at the 10 day WU forecast and the forecast from the link on this blog (not the US one the one that says Seattle), there is no way the northeastern Olypen is going to get as much rain as in any of the models you show. We rarely do. Why can’t the models - and you as well - be more accurate about predicting precipitation amounts in the Olympic rain shadow?

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  22. Thanks for sticking to the numbers, Cliff, and not fear-mongering about Californians. There is no one better at the data.

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  23. Bruce Kay
    “really weird..... the environment Canada measure for Skagit range went from 51% of normal april 1 to 15% for May 1.”

    I’m not saying this is what happened, but here’s a simplified and exaggerated hypothetical to consider:

    - Normal snowpack on April 1 is 40 inches.
    - Normal snowpack on May 1 is 10 inches.
    - with a just a little extra melting, the snowpack on May 1 might be 1.5” , only 8.5” less than average.
    - Represented on a graph: 15% of normal

    The actual values are likely much different, but the example demonstrates what can happen using percentages of normal.

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  24. The same New York Times that warned about the permanent California drought on account of global warming will now blame the deluge on global warming. In fact, anyone who bothers to look at the historical record will see that California has a natural, cyclical drought-drench climate.

    But if you're a "progressive," there's no need to actually look at any facts. You just "know," and you just lie. None of this has ever once been about climate. This is a political cult plain and simple.

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