November 29, 2017

Super Dark Days: Advice from a Meteorologist

Yesterday was an amazingly dark day.  In fact, according to UW meteorologist Mark Albright, it was the darkest day in Seattle (at the UW) since Dec. 8, 2015.  For the technically oriented among you, we had .61 MegaJoules per meter square yesterday, while on December  8, 2015 there was .57.   Essentially the same.  Typically this time of the year we have 2-3 times that amount.

The Seattle Space Needle PanoCan at noon yesterday says it all (see below).
Dark and dismal.

Why so dark?  We start with our northern latitude and the fact that we are within a month of the winter solstice.  Thus, we are near rock bottom for radiation reaching the top of the atmosphere.

Then we are in the cloudiest/stormiest time of the year.  End of November is our worst.

The visible satellite image and the regional radar at noon yesterday tells the story.  Thick clouds and rain greatly reduce the feeble solar radiation reaching the surface.

How bad was it?  Here are the radiation and weather measurements from the roof of my department in Seattle for the 72 hr ending 5 AM today (Wed.)  The bottom panel is solar radiation.

Almost nothing....I couldn't believe it when I first looked at the plot.    The third panel gives temperature (black line).   THE SUN WAS SO FEEBLE THAT THERE WAS NO DAYTIME WARMING.  In fact, temperature dropped during the day.

OK, the sun situation is really bad now.  What do you do?  

Listen to a meteorologist!

My first advice has nothing to do with weather.  Get out during the middle of the day.  Take a walk, go for a run, ride a bike.  Just get outside during the brightest time of the day...that really helps me.

Second, go to whether there are less clouds...and nearly every day there are places to get a lot more light.     For example, head for rain shadow areas in the lee of mountains..

During the winter storm season when southwesterly flow is prevalent, head towards the Olympic Rain Shadow, northeast of the Olympic Mountains.  Northern Whidbey Island, Sequim, Port Townsend, Victoria or the southern San Juan Island will do.

Here is an see the clearing NE of the Olympics?

After fronts go through and the winds turn more westerly, head east of the Cascade crest over the eastern slopes.  Places like Cle Elum. (see satellite image of such a situation).

But during the winter (November to February) don't do too far down into the Columbia Basin.  Why?  Because it often fills up with low clouds.  Very bad.
As shown below.

Sometimes in mid-winter under high pressure, the lowlands are full of low clouds, sometimes from the Willamette Valley to Bellingham.   But the mountains are in the clear! To get out of it, just go up in up to the passes or climb one of our hills.

Now, 10-20 times a year, we get a Puget Sound convergence zone and there are clouds (and often rain) right over Seattle (see below).  Want to escape the murk?  No problemo.  Just head north or south by 10 miles and you will be in sun!

Finally, head up into the snow in our mountains.   Snow reflects solar radiation and makes it much brighter, WHEN there is no active weather going on.

Pretty bright at Snoqualmie Summit!

There are more "secrets" I can tell you, but the message is clear.  Don't be passive in accepting a dark fate. You can do something about it.  90% of the time you can get to a LOT more light with a short drive.

Do what I do on one of the dark days....take a look at the visible satellite imagery (here), find the nearest bright spots, and make your plans!

He May Like the Dark Side.  You don't have to.


  1. Next week conditions could favor going to a higher elevation for sunshine. Fog and low clouds might bedevil the Puget Sound and Columbia basins but other areas will hopefully see lots of sunshine right when we need some.

  2. Cliff, is there any way to get good information on the depth/height of cloud tops. On Monday this week I was able to punch through some gloom around Portland by gaining only 1,000'.

    I know some of that could be influenced by the hills themselves. But that's the sort of information that could motivate some clever hiking choices.

  3. For working around the yard, or going for a walk, these are great. They do their normal job of protecting the eyes from bare branches that seem to disappear on a grey day, and also just brighten up everything. Any brand will do, but this price is easy on the wallet.

  4. Great suggestions, and as have been mentioned previously, there are alternatives such as using UVA "light boxes" for those who are housebound.

  5. Moses lake had a beautiful sunny day on Wednesday

  6. Yes, this is my least favorite time of year. I always look forward to April, but even February is a great improvement, with longer days, more sun, and the emergence of the crocuses.

  7. My PWS recorded a maximum irradiance of 39 w/m2 on 11/28. I do not remember having noted such a low maximum daily value since measurements began July 2016. Average maximum daily value from 11/20 thru 11/30 is 184 w/m2 and max value during the period (on 11/22) is 454 w/m2.

  8. Our photon-sensitive outdoor lighting has come on around 3PM lately - and this morning they are on again! Guess they might as well stay on all the time for Christmas lighting..

  9. Dr. Mass
    You brought this up(Super Dark Days),about the same time last year>
    I mentioned that is why "Seattle is the Suicide Capital of the lower 48 states",
    which was NOT true, but yet "How depressing".....

  10. Cliff, I love your blog and updates on KNKX, but I moved here from the Bay Area specifically because I was sick of the sun! I love the clouds and rain! So do many of us, including my wife (who is a UDub grad student and has seen you on campus, recognizing you by your distinctive voice), though admittedly, we're in the minority, humanity-wise. For me, the only uncomfortable season of the year in Seattle is the summer, which at least since I moved here in 2014 have been unbearably warm and bright! I wish it was this cool and "dark" 365/year, but at least it's much grayer (and greener) in general here than California. Keep these "gloomy" forecasts coming! (Full disclosure: I'm a moody pulp writer, but also a dog walker). Cheers.

  11. If only the California transplants who wish it was cool & dark year 'round would head farther north instead of adding to the congestion here.

  12. Seattle is my favorite city. I hardly ever leave my house, except to walk dogs. Thanks for the hospitality. I moved here for the climate, the beauty, the culture. Not the people. Of course, those who wish to live somewhere where it's sunny year round can always take my vacancy in California.

  13. Stay out of the mountains. They are too crowded these days!


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