Snowflake sci­ence

Truro Daily News - - WEATHER - – al­beit it, rarely – the col­umns or nee­dles are twisted? Twisted col­umns are also called Tsuzumi- shaped snow crys­tals. Der­rick – I’m glad you asked!

The week got off to quite a start. Mon­day was one of those days when our pre­cip­i­ta­tion couldn’t seem to make up its mind. Many of us ex­pe­ri­enced the gamut: snow to ice pel­lets to rain then back to snow; there were even re­ports of freez­ing rain.

As I ad­mired the patch­work of pastels on the radar screen I re­mem­bered a letter I re­ceived ear­lier in the fall about one type of fairly unique pre­cip­i­ta­tion. Der­rick Dezeeuw wrote, “I came home the other day and I thought my roses were cov­ered with some kind of in­sect, but no. I have never seen tubu­lar snowflakes be­fore. Thought I would share this with you.”

I’m glad you did Der­rick.

The life of a snow crys­tal of snowflake be­gins with nu­cle­ation around a dust par­ti­cle. The crys­tal slowly grows to a hexag­o­nal prism. As the plate gets larger it be­comes un­sta­ble and grows lit­tle arms at each cor­ner; that’s why most snowflakes are six- sided col­umns. The col­umns may be short and squat or long and thin – the long thin col­umns or nee­dles tend to be more pro­nounced when the tem­per­a­ture is around – 5 C. The nee­dles can be solid, hol­low, or par­tially hol­low, depend­ing on the tem­per­a­ture and mois- ture pro­file of the lay­ers of air above the ground.

Now if the del­i­cate ice crys­tals en­counter strong winds on their way down, the tiny arms can break off… fall­ing to the ground as lit­tle nee­dles.

Did you know that some­times

Cindy Day is Saltwire Net­work’s Chief Me­te­o­rol­o­gist.

A first glance, Der­rick Dezeeuw thought there were in­sects on the leaves of his rose bush. No bugs here Der­rick.

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