learning Snow Rate Vs Rain Rate

[Grimers]

Hi there,

I've always been curious, but does snow rate equal to 10 times the rain rate? e.g. 10 cm/hr equals 100 mm/hour or can the rate differ depending on atmospheric conditions?

Thanks,

William

[Grimers]

* 10 mm/hr.

[Paul]

It differs. 10:1 is rare in the UK as that's about the ratio for powder snow at just below freezing as a general rule, whereas our snow is often wetter, so you could be looking at 5:1 up to 10:1, perhaps even higher at even lower temperatures, but that would be rare in the UK away from mountains at least.

[Grimers]

3 minutes ago, Paul said:

It differs. 10:1 is rare in the UK as that's about the ratio for powder snow at just below freezing as a general rule, whereas our snow is often wetter, so you could be look at 5:1 up to 10:1, perhaps even higher at even lower temperatures, but that would be rare in the UK away from mountains at least.

Thanks for the explanation, Paul. That makes sense now as the snow flakes in wetter snow are normally larger hence a lower rate.

[Nick L]

Habyhints has a good guide:

http://www.theweatherprediction.com/habyhints/346/

Properly dry snow can give a ratio of up to 30:1 if you're really "lucky", but like Paul says, dry snow in this country is pretty rare. A typical guide would be somewhere between 5 and 10:1.

The basic physics is that dry snow forms in colder conditions, and colder air typically contains less moisture. As a result, snowflakes have more air pockets and are less dense - they use less of the available moisture than wet snow flakes do. As a result, you tend to get more dry snow flakes out of a given amount of moisture than wet snow flakes.

Edited November 16, 2016 by Nick L

[Grimers]

Interesting, thanks for the link, Nick L. So, basically less moisture is needed to produce heavier falls of dry than wet snow? That would explain why the snow we had on 20 December 2010 was quite dry.

Edited November 16, 2016 by Grimers