Snow tornadoes are so rare that only six have ever been captured on camera and very little is known about them.
These twisting columns of snow are closely related to waterspouts since they form over either frozen lakes or snow-covered areas.
For snow devils to occur, the necessary conditions include a colder air mass passing over a relatively warmer surface heated by sunlight, and a low-level wind shear (change of wind speed or direction with height) or colliding air currents to get the rising air to spin.
A warmer surface causes the snow or ice to form fog or steam, and if there is a column of colder, low-pressure air above this fog, it will begin to rise, and the wind shear or currents will cause it to rotate and begin to pick up loose snow forming the recognizable funnel shape.
The combination of these conditions is what makes snownadoes so rare and less intense than tornadoes.
Snownadoes have been reported as large as 30 feet wide, 45 feet high, and capable of lifting objects over 1,500 pounds.
They usually occur under or before a snow squall, meaning they are often indicators that more snow is on the way.
The one above, recorded by Tom Ording Dahl in Skjåk, Norway on March 1, 2016 was definitely not dangerous, but mesmerizing.
I once snowboarded a Snorenado.
It was a great day; conditions perfect, except for the wind.
A part of the mountain's fall line had matching gullies on either side which were almost 90 degrees off the prevailing NW winds.
I was competing in a Snowboarding Giant Slalom, at at that speed all you can really see is where you are going, and if clearly or not.
Next I knew, instead of taking the course's next right, I was inside a whirling vortex. I found myself being pulled up into it, into heights that would have scared Poe's least nervous narrators... (whatever that means).
I realized that I would keep going up, So I decided to pull a reverse 720 railgrab... and....
"The result was precisely what I had hoped it might be. As it is myself who now tells you this tale — as you see that I did escape — and as you are already in possession of the mode in which this escape was effected, and must therefore anticipate all that I have farther to say — I will bring my story quickly to conclusion."
I managed to board down INTO and upwards into the internal walls of the Snownado.
But as soon as I had done so, it had begun to move UP the mountain! I finally landed again at the starting gate, I thus lost 84 seconds in my final time, and, given that the snownado took me there via a shortcut across the second turn, (and as the ultimate insult), I was disqualified for having 'gone out of bounds!"
"But I now tell it to you — and I can scarcely expect you to put more faith in it than did the merry snowboarders of Lofoden."*
(T'was only then I realized that it was NO SNOWnado, but a SNOREnado, as it was just then I awoke.)
Such was my ASCENT "into the Maelstrom."
R.C.
(With apologies to E.A. Poe, A DESCENT INTO THE MAELSTRÖM, http://www.eapoe.org/works/mabbott/tom2t044.htm)
RC