April 15, 2016

ANOTHER Heat Wave. Will this Summer be a Repeat of the Last One?

It looks like quite a few of you will experience 80F again during the next few days.

Another major heat event is coming, with temperatures well into the 60s on Saturday, mid to upper 70s on Sunday, and even low 80s on Monday.    As you know, I have a lot of respect for the forecasts from weather.com and here are their numbers:

Considering that the average max temperature this time of the year is around 58F, we are talking about record territory for some days, with highs about 20-25F above normal.

The origin of this warmth?  You can guess it.  A strong ridge of high pressure over the West Coast (see the upper level map, 500 hPa level, at 2 PM Sunday).

I can't tell you how many people have told me they are worried about a repeat of last year:   very warm spring, water issues, low snowpack, wildfires galore, terrifying blobs, and all the other unpleasantness of last spring and summer.  They ask: are we seeing a permanent shift of our climate due to global warming?

What does the data and best science tell us?  This summer should be nothing like the last in terms of those unpleasant impacts.

The first thing to consider is while last winter brought normal precipitation, this year we had the wettest winter in Northwest history.  That makes a difference.
Reservoirs are full, groundwater is in good shape, rivers are running full.

Let's have some fun and do some more detailed comparisons.

The previous winter we had near normal or slightly below normal precipitation over the region.  This winter?  Here is the total from October 1, 2015 to April 14, 2016 precipitation anomaly (difference from normal).  This year, most of the region is above normal, with western Oregon and Washington much above normal.

Last year the snowpack was the worst in history.  This year it is normal, which means our full reservoirs will be topped off with lots of snow melt.   (see current snowpack figure for Washington below).

So, with wet conditions this winter and plenty of snow, river levels will be good into the summer.  Here is the 120 day stream fow forecast for eastern WA from the NWS River Forecast Center (percent of average).  We are talking about mid-August.  The Yakima River will be way above normal and the lowest rivers are near normal (about 80%).

The Yakima River authorities are forecasting plenty of water for farmers:  BOTH senior and junior rights holders.

What about heat?   We can start by looking at the water temperatures offshore.  Below are the weekly sea surface temperature (SST) anomalies from normal for last year and this year in April.   MUCH cooler till year.  Forget the blob.

A contributor to the warm water has been the VERY strong El Nino of the last year (and the moderate one the year before).  However, El Nino is weakening rapidly right now, so much so that the National Weather Service has released a La Nina alert for next winter.    A weakening El Nino should lead to cooling, both over the water and over land.  However, it will take some time (months) for its impacts to start to fade.

What about the persistent high pressure of last winter and spring?   Aren't we seeing some big ridges the last few weeks?   We have.  But the ridging and warmth have not been as steady and persistent as last  year....that is why we have gotten precipitation quite frequently.

Here is the last NMME seasonal  (June, July, August) forecasts provided by NOAA, based on an ensemble of seasonal climate models.

Precipitation is near normal.

Temperatures are moderately (.5 to 1C) above normal.  Last summer was 2-5C above normal.

Bottom line repeated:  we are in much better shape this summer.  Last summer was a fluke, resulting mainly from natural variability.  Global warming may have contributed a small about (perhaps .5C) to the warming, but it can not explain the key feature that caused all the trouble:   the persistent high pressure ridging.

So enjoy some very pleasant weather this weekend with no guilt.
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  1. Thank you! I've been so eager to know about the summer forecast and it seemed no news source was yet sharing any info, much unlike last year at this time.

  2. ENSO Neutral is predicted for late May early June, according to the latest El Nino rundown by NOAA. http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf.

    I am of the same thinking that these temp spikes are only temporary and will probably fall back to around normal for summer. Now that would be welcome after the fiery hot temps of summer in 2014 and in 2015. Where I was, we had two amazing runs of temp over 90. The first was a 16 day run over 90, and the last 8 or so over 100, around the 4th of July. The next heat wave was late July I think, into August. With 9 days in a row over 90. I would love to not see that again this year. Normal in Central Washington is generally 75-85(June into September), with temporary spikes of a couple days into 90 or 100, but only for a short time.

    Because of all the moisture the hills around here are green for the first time in years, pretty cool. And I agree, the blob is dead, and El Nino is way down, from 3.1 C at peak to 1.3 C this last week.

  3. Meteorology research has lost an icon, and I'm personally saddened at the loss of the first weather geek I ever "followed," though in his later years, when it became clear that he was a climate-change skeptic, I became less interested in what he had to say.

    Dr. William Gray, renowned hurricane researcher, has died at age 86. Cliff, I don't know if you knew Dr. Gray, but maybe you've got some connection to him as well. RIP, Dr. Gray. http://in.reuters.com/article/people-gray-idINKCN0XE04G

  4. This is off topic of summer, but I was interested to read that the National Weather Service forecasts will be start using lowercase letters as well as uppercase starting May 11:


  5. Looks like three or four more record high temps coming in the next few days for Seattle, but it's been years since we have set an overnight low record...

  6. Dr. Gray was very old school. I studied under Dr. Cobb. Way back then, global warming vs cooling was hotly debated. The opposing atmospheric forcing from aerosols and GH gasses were nearly balanced.

    The USEPA forced industry to remove most of the aerosols with baghouses and ESP. Aerosols quickly drop out of the atmosphere but CO2 does not. CO2 levels continue to rise while the aerosols drop out. The balance has tipped in favor of warming. I can't understand why Dr. Gray did not see it.

    Back in the early 70s, before 8am classes began, I'd watch brownish yellow clouds of NOX rise up from the I-25 corridor from the 3rd floor of Ross Hall. I recall many days when the haze (smog) was so bad I could see only a couple blocks down the road and the front range mountains were completely obscured. I'd drive up into the mountains and look back at Denver and cringe at the gunk in the air. The air we breath today is much, much better than it was 45 years ago.

    Back in the 90s, I worked in India for a time with BCCL (coal industry). I counted as many as 7 black smoke plumes undulating across the sky. There was/is no pollution control devices on their coal powered generators. The air was thick with silicate and coal dust. The water was filthy. The doctors I spoke with said most of the people are ill from air and water pollution. Sections of roads, railroads, homes and buildings collapsed from underground fires burning in abandoned coal mines. It was hellish. People died in their sleep when "cracks" would suddenly appear beneath their homes (Carbon monoxide and sulfates).

    When I hear politicians calling for closing or curtailing EPA, I cringe, as we all should. Unregulated industry will poison us to increase profit margins. It doesn't matter whether your living in a capitalist, socialist or communist economic system, industry will pollute unless we the people demand they don't. EPA is like the police of pollution. Take away the good cops and the crooks run the city.

    I do enjoy these extra-warm spring days. Come July, a +20 F over the norm day(s) will be unwelcome. Cooler SST should give us stronger marine pushes following heat waves. A day or two of heat is okay, its those long hot stretches that stress the body and plants.

  7. I hope it is a repeat of last summer. I am putting my tomatoes out today in mid April, just like the last two years. I always grow them from seeds in mid March, and they are getting too big for the window sills. Had a bumper crop both years.

    At worst, if the weather cools too much, the plants just sort of stagnate until the weather warms up again. In twenty years, I have never lost a plant due to cool weather. Fortunately, in West Seattle, I don't have to worry about late frosts due to my very close proximity to Puget Sound.

    Here is where you come in, Cliff. Please keep the daytime highs at least in the 60s. Thank you very much!

  8. "Global warming may have contributed a small about (perhaps .5C) to the warming, but it can not explain the key feature that caused all the trouble: the persistent high pressure ridging."

    Is it really that really settled or has research not caught up? What are the odds that we'd have the wettest winter on the heels of the warmest summer? I read frequently global warming will cause more extreme events so... what gives?

  9. That recent weekly anomaly graph shows a heat band right along the pineapple express. We may have more cool water in the northern Pacific, but if the fronts pull all their air from Hawaii...

    Anyone know of any industrial freezers renting bunk bed space? I'm sure those satisfy room licensing equivalent to apodments.

  10. Given that the Blob was a feature brought on by persistent ridging, I can't help being curious why, since we have very strong and unusual early season ridging, the same features aren't expected to bring the same results, a ridge-ey, hot summer.
    Can you address that?


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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