I have joked during past crazy weather days around here when we've got sun, rain, wind, hail, and even some lightning that if we were playing "Weather Bingo" about the only square left uncovered would be "dust storm."
Ahh, but 80 years ago this weekend, residents could have marked off the elusive square, provided they could see it.
On April 21-24, 1931, parts of Washington and Oregon were struck by an extraordinary dust storm, thanks to winter and summer colliding right in our neighborhood.
Donald C. Cameron with the Portland office of what was then known as the Weather Bureau (what is now the National Weather Service) wrote about "the Great Dust Storm in Washington and Oregon" in May, 1931 and gave the following setup:
"A week previous saw the end of a rather protracted wet spell in both States which was succeeded by clear skies and very low relative humidity under which the top layers of the soil had dried out very thoroughly."
A big arctic high settled in over Alberta with atmospheric pressures reaching 30.70" to 30.80". (Cold air is very dense and those arctic domes of high pressure are notorious for some very high readings.)
In the meantime, a strong thermal trough pushed up from the west coast. Just like cold air is dense, hot air isn't and can make for thermally-induced low pressure. (See weather maps depicting surface conditions.)
It made for incredible differences in pressure -- as much as 1.35" of mercury over the Great Basin or roughly 45 milibars, as the thermal low was centered over southern Oregon and northern California.
And as a result, very strong northeast winds raced across Eastern Oregon and Washington through Southwestern Washington and northern Oregon, and out to sea.
"...High winds were quite exceptional for the time and place," Cameron wrote. "Forest and brush files broke out suddenly over much of the territory invaded by the dust storm; the very low relative humidity and poor visibility made fire suppression very difficult."
The report didn't have too many wind reports, only to say that wind speeds in Pasco, Washington were recorded at 40 mph at 700 feet elevation and 77 mph at 1,400 feet elevation.
But the low humidity would make sense because as the air was likely dry anyway due to both the arctic high (cold air can't hold as much moisture) and became even drier when those winds crossed the Cascades and sank down the western slopes -- air gets drier as it sinks.
Cameron also posted some observations logged by ships just offshore in the Pacific.
From the "Albertolite" just off the central Oregon coast on April 22, 1931: "Visibility so low it necessitated navigating as in a fog. At this time the atmosphere was filed with fine particles of dust or sand and there was a distinct odor of smoke."
And from the "Emma Alexnader" nearby: "Dust covering the entire ship and shutting off visibility to the extent that it was necessary to sound the whistle."
But even ships off the Northern California coast found dust as well. From the "Somme" on April 23: "Found heavy coat of fine, brown dust that looked like volcanic ash."
Could something like that happen today? They do still get dust storms on occasion in Eastern Washington.
Here is what a satellite image photo showed of that storm:
So I suppose if conditions were just right, we could see something like that again someday. Enough to at least keep the option on the weather bingo card :)
Special thanks to UW Research Meteorologist Mark Albright for sending me the NOAA article on the storm.