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Friday, December 25, 2015

The reason for the wrong kind snow

A Christmas post of a different kind.

The article on the wrong kind of snow is worth reading, on Wikipedia.  Yes, it's something found on Wikipedia, and I just found it this Christmas morning, while looking at Types of snow.  (remember, Wikipedia is wonderful, no doubt about it)

The reason for the wrong kind of snow, which is rare in England, was the extreme cold.  Very cold air makes powder snow, something the railroads and plows are not used to.

This shows up even using the monthly data, which is remarkable.



When the air causing it to snow is very cold, the snow can be powder, instead of the wet stuff the British think of as snow.

This happened again, since the original story, and they are still using the term.


People always want to know the last time we had such heavy snowfall
Questions like this are practically impossible to answer accurately because every snow event is different. And some parts of the country are better equipped to cope with the stuff than are others. 
For instance, a ten-inch snowfall in London is not only much rarer than a similar fall in the Scottish highlands, but it will also affect a rather larger number of people.
The last occasions that London and the Home Counties were hit so badly were in February 1991 and January 1987. During the 1991 event level snow lay 12 inches deep in central London, and on January 12-13, 1987, the deepest snow was in south Essex, Kent, Surrey and south London with 22 inches reported in the Maidstone and Gillingham areas. Yesterday, central London had six inches while the Surrey suburbs reported 10 to 13 inches.

The important fact from all this is about what does "heavy snow" even mean?

It does not mean the weight/water content of the snow.  Heavy snow means lots of snow, which is almost always powdery snow, which is the light fluffy snow.  So heavy snow means light snow, but lots of it.

More on this to come.  Because heavy snowfall is not found on Wikipedia.

Did you know that was coming?

Heavy snow redirects, but makes no sense at all.

Heavy snow warming does exist, stating the NWS uses it for "snowfall rates of 4 inches (10 cm) or more in 12 hours, or 6 inches (15 cm) or more in 24 hours".

So both rate and amount are involved, but not the kind of snow falling.