Where snow falls.

[dan]

I've been wondering, why can't it snow in Hamilton? I mean it has snowed in Christchurch (which is at sea level) with temps as high as 5 degrees. And yet there have been plenty of occasions here in Hamilton where it has been -3 degrees or so, raining, and yet nothing even close to snow. I imagine Hamilton would be slightly higher altitude than Christchurch. So does it have something to do with thickness levels? Something to do with being further South?
Any kind of light shed on this question would be great.

[Tornado Tim]

It apparently snowed in Hamilton around the 1950's, wonder if it will happen again.
From my knowledge the clouds need to be well below freezing for snow to form and then drop.
The reason i think why us Hamiltonians dont get snow is because the temps of clouds is too warm and quite possibly we are not high enough so any cloud that might have the formation of snow will fall as snow then melt to rain before it hits the ground.

[tich]

It's not just because of Hamilton's latitude that it almost never gets snow - it's also sheltered from the snow bearing very cold southerlies by the central high country and mountains.
I've read that it snowed in rural areas not far from Hamilton in 1980, and I personally remember a very cold day at the end of May 1989, when it wasn't far from snowing in the city, an Mt Pirongia had a good coating.

[tgsnoopy]

I can think of occasions in the last few years when it's snowed on Pirongia. It has sufficient altitude to receive it, but Hamilton City is a different story, next to no altitude.

I'd love to experience a freak system that dumped snow on Hamilton.

[NZstorm]

Most of the precip in Hamilton actually starts out as a snow flake.

I suspect snow is remotely possible in Hamilton, maybe a warm advective set up one day! Those cold showery SW'ers get a bit nippy too. I have seen wet snow falling in Taumarunui. (170M)

[Storm Struck]

I dont think its possible to get snow falling to sea level in christchurch with temperatures of 5C, its always got to be in that temperate bracket of -1C - 2C.
Inland areas are a different story though.

[Richard]

That's true Jason,its got to be 2C and under before it can snow,even inland.The reason snow falls to sea level in CHCH and to north along the Pegasus Bay coast is that during periods of cold southerly outbreaks the wind direction tends to come more from the SW.Example of this,in Rangiora a southerly wind is a very rare event,in fact i dont ever remember one in the 30 years i lived there.Because this SW wind has come from a slightly higher elevation,it doesn't have time to warm enough,hence snow on the beaches which in its self appears to becoming more common over the last 10 years or so.

[Michael]

I say Hamilton(and Auckland) would get snow in a situation of a low centre moving north from the south where west winds turn S with a warm or occluded front passing north over the above mentioned areas and the cold wind trapped in a local circulation would bring it about though it probably would last long because the wind would change again either SE or SW quickly and it would stop.

[mikestormchaser]

Hmm i cant really see it snowing anytime soon regardless up that way, sorry but you guys are rather warm up that way..

[TonyT]

That's true Jason,its got to be 2C and under before it can snow,even inland.The reason snow falls to sea level in CHCH and to north along the Pegasus Bay coast is that during periods of cold southerly outbreaks the wind direction tends to come more from the SW.Example of this,in Rangiora a southerly wind is a very rare event,in fact i dont ever remember one in the 30 years i lived there.Because this SW wind has come from a slightly higher elevation,it doesn't have time to warm enough,hence snow on the beaches which in its self appears to becoming more common over the last 10 years or so.

Um, no.

I cant vouch for the accuracy of your wind direction recall, but if southerly winds are rare in Rangiora then thats most probably due to orographic flow around Banks Peninsula. The same reason southeast winds are very rare in Christchurch city. You certainly dont need to go too far north and northeast of Rangiora to get plenty of southerly (and here in Amberley a fair number of southeasterly) winds, which are more likely to put snow down to sea level than the southwest winds are.

i think Tich is right - its the orographic sheltering of Hamilton from the coldest winds which is probably the biggest reason why it misses out.

[dan]

Thanks for the reply's guys. Yes i can see it now, the grand southerly has all the moisture and cold sucked out of it by the central high country before it gets to Hamilton. A few years ago I saw snow just out of Cambridge and in Tokoroa, that was something.

[Richard]

That's true Jason,its got to be 2C and under before it can snow,even inland.The reason snow falls to sea level in CHCH and to north along the Pegasus Bay coast is that during periods of cold southerly outbreaks the wind direction tends to come more from the SW.Example of this,in Rangiora a southerly wind is a very rare event,in fact i dont ever remember one in the 30 years i lived there.Because this SW wind has come from a slightly higher elevation,it doesn't have time to warm enough,hence snow on the beaches which in its self appears to becoming more common over the last 10 years or so.

Um, no.

I cant vouch for the accuracy of your wind direction recall, but if southerly winds are rare in Rangiora then thats most probably due to orographic flow around Banks Peninsula. The same reason southeast winds are very rare in Christchurch city. You certainly dont need to go too far north and northeast of Rangiora to get plenty of southerly (and here in Amberley a fair number of southeasterly) winds, which are more likely to put snow down to sea level than the southwest winds are.

Yes i agree with you that orographic air flow around Banks Peninsula would have some influence ,but i believe the mountain ranges running from Mt Oxford through to Mt Gray is the main contributor in causing such a deviation in wind direction,Rangiora is just too far away from Banks Peninsula to have much of an influence.
A southwest air stream during winter tends to bring precipitation whether or not in snow form to mainly coastal areas,summer SW precip inland.Polar southerly air streams will bring lower snow levels than a SE air stream,simple fact. SE air streams do tend to bring heavy snowfalls though,because they tend to carry more moisture but only above 100m minimum,all the times i've seen snow falls on the beaches of Pegasus Bay there has always being a SW blowing,even 7 kms south of Amberley.

[spwill]

I dont think its possible to get snow falling to sea level in christchurch with temperatures of 5C, its always got to be in that temperate bracket of -1C - 2C.
Inland areas are a different story though.

Dewpoint temperatures are generally lower inland , snow flakes survive much better in temps above 0C in dryer air.