Hail V Snow

highdef · 29-12-2011 2:36am #1

I've seen a lot of comments lately saying things such as "snow at higher levels and hail nearer sea level"....or something along those lines anyway. I was just wondering, how does this happen? I mean, say it's snowing at 300m....how can this then be hail at near sea level? I can't understand how there can be such a difference in precipitation type in a few hundred metres. The way that they are formed is very much different so I am finding it difficult how the precip type can be so different over such a small difference in altitude. Maybe I am not understanding it correctly but from what I have read in forecasts, this is what is often forecast.

Su Campu · 29-12-2011 2:44am

I think may have said that recently, which was wrong. The showers coming in off the Atlantic will be of hail and rain if upper temperatures are cold enough to generate the hail. I meant that the "rain" would fall as snow higher up, mixed with hail, and the only frozen precipitation people at sea level would get would be the hail (mixed with the rain).

It is possible that hail falls on higher ground and only rain at lower levels, but this would be if the hail melts to rain by the time it reaches low levels.

Sponge Bob · 29-12-2011 2:52am

Air is layered. Every day a layer analyser called a "Sonde" is launched to see where these layers meet.

http://www.met.ie/about/valentiaobservatory/radiosonde.asp

Something that starts as a raindrop can turn to snow in a lower layer and to hail further down. Hail often starts as snow but is blown up into a freezing layer before it gains enough weight to fall against an updrafting wind.

Tornados, essentially violent warm air and warm moisture systems, can produce massive hailstones. The biggest hailstone ever fell in June 2007 .

http://www.crh.noaa.gov/fsd/?n=hail2007aug21_dante

Deep Easterly · 29-12-2011 5:00am

Sponge Bob wrote: »

Air is layered. Every day a layer analyser called a "Sonde" is launched to see where these layers meet.

http://www.met.ie/about/valentiaobservatory/radiosonde.asp

Something that starts as a raindrop can turn to snow in a lower layer and to hail further down.

Snow is created from minute ice crystals within a cloud. A raindrop falling into a sub-freezing layer lower down will not turn into snow.

Iancar29 · 29-12-2011 1:25pm

And the biggest hail i ever got MY hands on! :cool:

227132_10150267092971718_631736717_9535245_2783148_n.jpg

Su Campu · 29-12-2011 3:04pm

Sponge Bob wrote: »

Air is layered. Every day a layer analyser called a "Sonde" is launched to see where these layers meet.

http://www.met.ie/about/valentiaobservatory/radiosonde.asp

Something that starts as a raindrop can turn to snow in a lower layer and to hail further down. Hail often starts as snow but is blown up into a freezing layer before it gains enough weight to fall against an updrafting wind.

Tornados, essentially violent warm air and warm moisture systems, can produce massive hailstones. The biggest hailstone ever fell in June 2007 .

http://www.crh.noaa.gov/fsd/?n=hail2007aug21_dante

I think you have a few things backwards there. Hail doesn't form low down, it forms high up in the higher parts of cumulonimus clouds, where a frozen particle becomes bigger as supercooled water freezes on it, producing layers of rime, like an onion. The stronger the updrafts the longer this growing hailstone remains jolted around, until eventually gravity wins out.

Snow usually turns to rain lower down, not the other way around. If you have rain from a warm layer falling through a narrow sub-zero layer at the surface then it will freeze on contact, which is called freezing rain, and is probably the most dangerous situation.

Hail V Snow

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