On a roll in Kings County
While there’s still some snow on the ground in some places, I wanted to share an email I received from an old colleague last week.
“These photos were taken beside a steep bank near Coldbrook, Kings County. The snow was sticky; pieces that became loose rolled down the bank, creating these discs. Fascinating to see.” Best regards, Peter Eaton
They don’t appear very often but when they do, they get everybody talking: snow rollers!
A snow roller is a rare meteorological phenomenon where snowballs form naturally when chunks of snow are blown along the ground by the wind. Once they get moving, they pick up more snow along the way; it’s a lot like rolling snowballs to make a snowman.
However, unlike snowballs made by people, snow rollers are usually cylindrical and are often hollow; the inner layers, which are the first layers to form, are weak and thin compared to the outer layers and can easily be blown away.
Their hollow centre makes them look like a swiss roll. Larger snow rollers can measure up to one metre in diameter. While most snow rollers are found in wide-open fields, now and again, we are treated to one where we can have a good look without jumping fences.
The basic ingredients still apply: the ground must be covered by a layer of ice.
The layer of ice must be covered by wet, loose snow with a temperature near the freezing point. The wind must be strong enough to move the snow rollers but not strong enough to blow them too fast. The ideal wind speed is about 45 kilometres per hour and alternatively, gravity can move the snow rollers.
Because of this last condition, snow rollers are more common in hilly areas, as was the case in Peter’s photos.
What’s left of the snow in Kings County will get washed away by an approaching wind and rain system this weekend.
For those of us hoping to make our own snowballs, I’m watching a developing system that could whiten things up for us on Tuesday. Stay tuned.