The Children’s Blizzard, by David Laskin
(p.75) Chapter Three: Disturbance
Though the convulsions of the atmosphere are often complex and multifaceted, extreme cold has a fairly simple formula. Diminish the duration and intensity of sunlight, deflect winds carrying milder currents, level the surface of the land, wait long enough, and you’re sure to end up with a pool of dense, calm, frigid air.
Just to be sure, add a layer of clean white snow so that what light does reach the ground is reflected back into the atmosphere before the earth can absorb its warmth. If, on top of all this, you have clear skies above you, temperatures will plunge spectacularly at night, as the atmosphere’s infrared energy radiates off into space. Of course, there are other recipes for outbreaks of cold weather, including the movement of fronts and pressure systems, but this is the easiest and surest.
A week or so of these conditions, and the cold will be fierce, unyielding, and deadly. All of these conditions came into alignment over the Canadian interior during the first days of January 1888. Take out a map of Canada (p.76) and run your finger along the 60th parallel, the line that runs from the Gulf of Alaska to Hudson Bay, neatly separating the tops of British Columbia, Alberta, Saskatchewan, and Manitoba from the bottoms of the Yukon and the Northwest Territories. This is one of the world’s perfect breeding grounds for cold.
At this latitude, on the day of the winter solstice, the sun remains above the horizon for a total of 5.6 hours. For the other 18.4 hours of the day, it’s either pitch dark, or an eerie purplish twilight, depending on the state of the atmosphere. But calling those 5.6 hours “sunshine” is a bit misleading. Even if it rises into a perfectly clear sky, the winter solstice sun over Fort Smith, Fort Resolution, Fort Simpson, Fort Liard, and Watson Lake provides essentially no solar energy.
There is light, but because the rays are so slanted in winter this far north, very little solar radiation is absorbed at the surface to heat the ground. Fort Simpson, which sits on the Mackenzie River in the Northwest Territories, hundreds of miles, and two mountain ranges away from the moderating influence of the Pacific Ocean, has an average daily temperature of 11 degrees below zero in December, and slightly over 16 below in January.
But at the start of January 1888, it was considerably colder than the average. With high pressure bearing down on western Canada, surface winds were light. Nothing disturbed the vast shallow pool of cold air that settled over the snow-covered plains and lakes. The longer the atmosphere stagnated, the colder it became.
On January 3, the temperature hit 35 below zero east of Fort Simpson. Gradually, over the next few days, the cold air mass expanded and flowed southward like a glacier of sluggish gas. By Sunday, January 8, the lobes of cold had pushed as far south as Medicine Hat in Alberta, about 70 miles from the Montana border, and as far east as Qu’Appelle, due north of the Montana/North Dakota line.
And there it sat, a pool of dry, stagnant, and exceedingly cold air, too heavy to rise into the warmer air above it, too inert to mix with the milder air masses around it. Imagine a blob of invisible subzero mercury, sealed and quivering over a quarter of a continent. (p.77) Stable is the word meteorologists use for an air mass of this sort—but nothing in the atmosphere is stable forever. A minor shift in the flow miles above the frozen surface, if conditions were ripe, would be enough to shatter the cold’s fierce grip. But it wasn’t going to go quietly.
Constantly and futilely, the earth’s atmosphere seeks to achieve equilibrium. Weather is the turbulent means to this perfect, hopeless end. Contrasting temperatures try to balance out to one uniform temperature, pressure differences strive for resolution, winds blow in a vain attempt to finally calm down global tensions. All of this is enormously complicated by the ceaseless rotation of the planet.
Weather is the steam the atmosphere lets off as it heaves itself, again and again, into a more comfortable position. Weather keeps happening because the equilibrium of the atmosphere keeps getting messed up. It doesn’t help that the planet itself is irregular, with crumpled solid chunks of land randomly interrupting the smooth liquid surface of the oceans. Equilibrium doesn’t stand a chance against all these complex interacting variables.
There’s so much going on out there, and up there, that the very striving for equilibrium is erratic, chaotic. There are patterns, of course, repetitions and cycles, long stretches of monotony and eerie symmetries, but weather, by its very nature, lacks a fixed overall structure. It’s a stream that perpetually remakes the channel of its flow.
Shortly after Christmas 1887, a ripple developed in the flow, about six miles above the surface, that would in time dislodge the frigid air massing over interior Canada. Today, accustomed as we are to the patter of televised weather forecasts, it’s easy to reduce the violent and deadly blizzard that resulted from this disturbance to a canned meteorological scenario, the low dropping down from Canada and (p.78) tracking south and east across the Upper Midwest before swinging to the north, the blast of wind and snow that accompanied the passage of the cold front, the outbreak of arctic air that surged as far south as Texas.
But in a way, this description only trivializes what was really happening in the air and on the ground. A storm, any storm, involves the entire atmosphere. Meteorologists refer to the atmosphere as a “continuous fluid,” or in the words of chaos theorist Edward N. Lorenz, a “thermally driven rotating fluid system,” and the phrases are apt.
In weather, everything connects. Connects first of all to the sun. The uneven distribution of the sun’s radiation is what causes temperature differences in the first place. As areas of higher and lower pressure develop in response to these temperature differences, winds begin to kick up, blowing from high pressure to low pressure (an extreme example of this is a pressurized container like a can of hair spray: Think of how the small parcel of high-pressure air rushes out into the lower-pressure air around it when the valve is released).
The ripple that shoved the cold air out of Canada was born of the interaction between air masses of contrasting temperature and pressure, and so, in a larger sense, was the upper-level flow of air that swept up the ripple and carried it down the spine of the continent. That upper-level flow, commonly known as the polar jet, circles the globe from west to east at altitudes of between six and nine miles.
The jet stream is a natural boundary marker, an atmospheric river flowing between the region of warm subtropical air to the south, and cold polar air to the north. The sharper the temperature contrast between those two regions, the faster the river flows. In winter, the course of the river drops south, and its current stiffens, winter speeds of 75 mph are common, though it has been clocked at 200 mph.
By January, the vigorous winter jet is down around the 50th parallel, right over America’s northern tier of states. Or rather it would be over the northern tier, if it flowed in a straight line, but in fact, the jet meanders around the world in a series of (p.79) immense loops, each of which spans some three thousand or so miles. These loops, or long waves, as meteorologists call them, form as the jet gets squeezed or stretched by the prominent irregularities on the earth’s surface, like major mountain ranges or the ocean basins.
Typically, three to five long waves are slowly moving and evolving around the earth at any given moment. As these waves interact with the jet stream that flows through them, great eddies of air known as cyclones (lows) and anticyclones (highs) spin up, which themselves warp the whole pattern of waves.
High pressure at the surface, which is associated with warm air aloft, creates a poleward bulge in the flow called a ridge, an arc that slopes to the north on its westward flank, peaks at the top of the high, and then descends southward; similarly, low pressure at the surface, associated with cold air aloft, sends the jet plunging south in an arcing trough that bottoms out around the base of the low.
When forecasters speak of a “ridge of high pressure,” or a “trough of low pressure,” what they’re talking about are the peaks and valleys of the long waves that distort the west-to-east progress of the upper flow. Each long wave is measured by its wavelength (the distance from ridge to ridge and trough to trough) and its amplitude (how far north or south the loops are deflected).
During the first week of January 1888, as Etta Shattuck was teaching her last day of school in the Bright Hope school district, and Anna Kaufmann’s three older sons were dutifully walking back and forth over the hard-packed snow to Mr. Cotton’s schoolhouse, and eight-year-old Walter Allen was studying his fool head off in Groton, a dome of intense high pressure in western North America buckled the polar jet into a high-amplitude ridge.
This pattern might have hung in for a week or more before the long wave drifted away, or gradually weakened, and we never would have heard a thing about it. The reason it didn’t happen this way is that a sudden shot of energy surged into a segment of the jet and caused (p.80) the core of the current to accelerate rapidly, like a bullet train rocketing through a tunnel of air, a tunnel that is moving as well in the same direction, only more slowly.
This atmospheric bullet train is called a jet maximum or jet streak. It’s hard to pinpoint exactly how and when a particular jet streak takes off, though there are several scenarios typically at play. Six miles above the Arctic, vortices of cold air spin around columns of even colder air, picture an atmospheric whirlpool six hundred miles across, and it’s possible that one of these vortices, known as cold-core lows, drifted south until it collided with the ridge in the jet stream and then unraveled its energy into a jet streak.
Or a disturbance off the east coast of Asia, born of the contrast between mild maritime air over the Sea of Japan, and cold continental air blowing off the deserts of Mongolia, might have been the jet streak’s energy source.
From January 5 through 8, the observer at the U.S. Army Signal Corps station at Anvik, in west-central Alaska, recorded high northeast winds and snow, which may well have been a sign of the jet streak careening in from the Pacific. Or the band of enhanced winds might have risen out of the ghost of a storm that had burst and dissipated over Europe or central Asia days earlier, and then fed its ephemeral remains into the jet.
In any case, some disturbance created a crimp, or “short wave,” in the smooth undulation of a long wave, and at the heart of this crimp a jet streak spurted forward. As long as it was over the Pacific, or sailing up the west side of the North American ridge, the jet streak existed as pure potential, the tightening coils of an ineffable spring. Its potential would be released only if, and when, the jet streak encountered the right conditions to reinvigorate it.
A week into January, those conditions presented themselves, one after another, in quick succession, like a run of losing poker hands. There was no reason why one bad hand had to follow another, the deck was shuffled and dealt anew each time. It was just the luck of the cards, loss after loss that finally compounded into catastrophe.
(p.81) On Tuesday, January 10, the jet stream with its embedded jet streak, having crested the ridge somewhere up in the northern reaches of British Columbia or the southern reaches of the Yukon, began diving southeast into western Alberta. It was here that the flow encountered the immense irregular wall of the Rocky Mountains, the first losing hand. The mountains squeezed and deflected the current, altering its temperature and pressure.
As the flow descended the eastern flank of the Canadian Rockies, the air warmed, and as it warmed, it dropped the air pressure at the surface. Some disturbances, known as leeside lows because they form on the eastern or leeward side of the Rockies, spring to life in this way. But given the intensity of the storm that followed, it seems more likely that the remnants of an older disturbance had come in from the Pacific and amplified when the jet crossed the Rockies.
As the upper flow crested the jagged obstacle of the mountain range and soared over the great flat expanses of the North American plains, it sent an immense vortex spinning counterclockwise all the way down to the surface. The ghost had come back to life. Propelled by the high pressure building in behind it, the low worked its way southeast down the tapering lower half of Alberta on Tuesday, intensifying as it moved.
The air was so cold that it had very limited capacity to hold moisture, so not much snow fell. That would come later, when the vortex fastened onto a stream of moist air coming up from the south. The stronger the low became, the more surface air it pulled toward the center of its vortex. You’d think that the low would eventually “fill,” by pulling in enough air to raise its pressure, and thus fizzle itself out. The reason this didn’t happen was because of the way the jet streak was roiling the flow six miles up.
To continue with the bullet train and tunnel analogy: Air moving through the jet stream’s tunnel was forced to converge as it got sucked into the rear, or “entrance region,” of the jet streak’s bullet train; but when the air was hurtled out the nose, or “exit region,” of the train, it spread or diverged from the core of the (p.82) flow like a delta at the mouth of a high-speed river of air. The diverging flow aloft acted like a pump, which evacuated the air below it.
The winds converging at the surface got sucked up into the vortex of the low, and then, due to the force of the jet streak, spewed out the top by the diverging upper-level winds. With a greater mass of air streaming out the top of the funnel than feeding into the bottom, the air pressure at the surface kept dropping. Meteorologists call this upper air support for a developing storm.
The chance alignment of the low and the jet streak’s exit region was the second losing hand. Not only did the jet amplify the low, but it forced it to take a steady course to the southeast. With the jet feeding and steering it, the disturbance was cranking up into a powerful and fast-moving low pressure system, a “mid-latitude cyclone” in meteorological parlance.
Sometime during the first hours of Wednesday, January 11, the advancing low crossed the U.S. border and began to cause the air pressure over northeastern Montana to fall. All that day, it continued to churn southward, until by nightfall on Wednesday, there was a well-defined trough of low pressure radiating out from the vicinity of Fort Keogh, near Miles City, Montana, and extending north into southern Alberta and British Columbia, and south to Colorado.
By itself, the strengthening low would have kicked up some stiff wind on the Great Plains, blown the snow already on the ground into drifts, maybe spat out a few inches of new snow before subsiding: a typical midwinter storm; certainly nothing historic. But as it dug deeper into U.S. territory, the low uncovered a source of highly explosive fuel that boosted its power exponentially.
To the north of the low, up in central and northern Alberta, that pool of arctic air had hardly budged for a week now, and the longer it stagnated, the colder it got. To the south, a mass of unseasonably mild and humid air from the Gulf of Mexico was beginning to stream up over Texas and Oklahoma. The potential energy in the temperature differential between these two sharply contrasting air (p.83) masses was enormous.
In order for that potential energy to be converted into the kinetic energy of violent weather, something had to bring the air masses together, the more sudden their encounter, the more violent the weather would be. That something was the intensifying low. The fact that the low happened to wander down between these two air masses, at this particular moment in time, was the third bad hand. The hand that finally and abruptly ended the game.
End Of Chapter Three