Reposted from the Cliff Mass Weather Blog
I have been hearing from a lot of folks suggesting that our weekends have been wetter than our weekdays, and asking me whether this was true.
So is it true? Are the weather gods preferentially punishing Puget Sound residents over the weekend?
Are the weather gods punishing us?
Let’s find out!
To do this, I secured the daily precipitation statistics at Seattle-Tacoma Airport for May and June so far–43 days in all.
For the full period, there was 4.04 inches at Sea-Tac for .09 inches per day.
For the 31 weekdays, there was 1.72 inches in the rain gauge, or .05 inches per day
But for the 12 weekend days, there was 2.32 inches or .19 inches per day.
Yikes! It is true! The weekends have been wetter, with nearly FOUR TIMES MORE PRECIPITATION PER DAY THAN DURING THE WEEKDAYS.
Good reason to complain. But is this a real effect or just chance?
There have been a number of investigations of this serious topic, a recent one led by one of my ex-students: Professor David Schultz of the University of Manchester. Their conclusions based on examining the data from 219 stations across the U.S for the period 1951-1992 was:
“neither the occurrence nor amount of precipitation significantly depends on the day of the week”
A conclusion illustrated by this figure from their paper:
Other earlier papers have produced contradictory results. Some have suggested that weekly variations in pollutants from industrial processes, aviation, and driving would influence precipitation processes, thus producing a weak weekly precipitation cycle. But lets face it, such effects would be greatly minimized in this period of COVID-19 shutdowns and the protest-related fires did not start until late in May. A plot of the concentration of particulates over Seattle does not suggest a weekly signal at all, with relatively clean air over Puget Sound for the period (see below, 5-10 is clean air).
I suspect strongly that this precipitation pattern is just bad luck, an unfortunately roll of the meteorological dice and will not continue into the summer. Yes, it is raining today. But according to the excellent weather.com forecast, tomorrow (Sunday) should be mainly dry, showers will be around Monday and Tuesday, and next weekend should be dry.
But providing an offering to your favorite weather god might not be such a bad idea, something meteorologists like myself are well practiced at.
In my department, we instruct the uninitiated how to appease the weather gods
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I would like to study whether or not Environment Canada over predicts sunny weather for the weekends. It seems they do but the forecasts change so frequently that it is not possible to say exactly which forecast is the one to count. Much like screening tree ring datasets, you could pick and choose your forecasts to get pretty much whatever result you wanted.
Bit like here in the UK where it is thought that Bank Holidays are wetter than normal days, so people spend weeks looking forward to a three day weekend only to find it tips it down with rain.
A few years ago after the Met Office had spent the early part of the year bleating on about how it was going to be the “hottest driest” summer ever we had a cold wet summer so the Met office changed it to it going to rain till well into September so the August Bank Holiday would be a washout.
Come the end of the month and low the weekend was warm and sunny over the whole country.
James Bull
“So is it true? Are the weather gods preferentially punishing Puget Sound residents over the weekend?”
If the weather gods are not punishing Seattle, they should be!
May the PSCZ (Puget Sound Convergence Zone) park over downtown Seattle and Capitol Hill district for the rest of the summer. There, Curse armed and launched.
In case you don’t know, the wind flow around the Olympics can cause an unusual weather phenomenon by forcing winds to converge on the lee side of the mountains forming an approximately ten-mile wide area of enhanced clouds and rain called the Puget Sound Convergence Zone which stretches across the sound sometimes to the foothills of the Cascade Mountains. Occasionally it can be so pronounced that north and south of the PSCZ the skies can be partly cloudy and in the PSCZ the skies will be overcast with light rain and drizzle.
In six years of school in Scotland I do recall that summer was an annual event and usually occured on a Thursday.
Cheers
Mike
Decade or so ago a local weatherman in Portland, OR looked at the data for the Portland area. He concluded yes it does rain more on the weekends. Think he looked over a couple years worth of data but memory is fuzzy on exactly what he said.
The meteorologists in the Portland Oregon area (both in the University of Oregon and National Weather Service) have done studies that prove everyone’s hunch that it DOES rain (slightly) more during the Rose Festival (early June) than the weeks before or after. They attribute it to the fact that that is about when the mean position of the polar front (weak though it may be that time of the year) transitions across the city, finally moving north of the city to end in northern BC/Southern Alaska
Oh, and by the way, Summer usually doesn’t start in earnest around here until the 4th of July. Portland gets less rain in July than any other U.S. city outside of the Desert Southwest. (0.57″). Summers here are beautiful; lots of sunshine, little rain, average high 81℉. [we aren’t going to talk about the dreary winters]
It’s true! It’s true! The crown has made it clear.
The climate must be perfect all the year.
A law was made a distant moon ago here:
July and August cannot be too hot.
And there’s a legal limit to the snow here
In Camelot.
The winter is forbidden till December
And exits March the second on the dot.
By order, summer lingers through September
In Camelot.
Camelot! Camelot!
I know it sounds a bit bizarre,
But in Camelot, Camelot
That’s how conditions are.
The rain may never fall till after sundown.
By eight, the morning fog must disappear.
In short, there’s simply not
A more congenial spot
For happily-ever-aftering than here
In Camelot.
Camelot! Camelot!
I know it gives a person pause,
But in Camelot, Camelot
Those are the legal laws.
The snow may never slush upon the hillside.
By nine p.m. the moonlight must appear.
In short, there’s simply not
A more congenial spot
For happily-ever-aftering than here
In Camelot.
Nicely done Mark but you forgot to mention how this was all decreed so the crown could hoard the coal and oil and dispense it to the Royals and all their elitist friends.
Was that before or after the introduction of the Gregorian calendar?