London: 7 degrees and light snow!?

compsys

Is it really possible? Yahoo! current weather conditions are usually spot on.

http://weather.yahoo.com/england/greater-london/london-44418/?unit=c

thetonynator

I dont think snow is possible above 4 degrees, but i could be wrong . .

smodgley

thetonynator wrote: »

I dont think snow is possible above 4 degrees, but i could be wrong . .

http://www.sciencebits.com/SnowAboveFreezing

BEASTERLY

thetonynator wrote: »

I dont think snow is possible above 4 degrees, but i could be wrong . .

It is but only in coleraine.

fizzycyst

the link has humidity at 93% so not a chance

BEASTERLY

Yea the more humid it is to closer the dewpoints will be to the actual temperatures, if humidty is low dew points cam remain blow zero if temps are relatively high, allowing snow to be possible. But if DP's go above 0 well then snow is practically impossible.

I wonder what the max temp is where you can have dew points below 0, i presume this would be most easily achieved ironically in a desert where the humidity is close to 0%

EDIT:i came up with a good idea for making our snow less marginal. Here it is, in marginal snow events if we all go down to the plant hire store and rent a dehumidifier and turn them all on out in our back garden we might be able to 'dry' out the air and lower the Dewpoints!:D:D Whose with me?

thetonynator

BEASTERLY wrote: »

Yea the more humid it is to closer the dewpoints will be to the actual temperatures, if humidty is low dew points cam remain blow zero if temps are relatively high, allowing snow to be possible. But if DP's go above 0 well then snow is practically impossible.

I wonder what the max temp is where you can have dew points below 0, i presume this would be most easily achieved ironically in a desert where the humidity is close to 0%

I think i saw dubai at 30 degrees with a negative DP over the summer, but it could have been a mistake.

M.T. Cranium

I recorded snow once at 42 deg F, when I was a teenaged weather observer. If the weather system is not a very powerful one, I think you can get snow reaching the ground instead of melting, due to a lack of mixing above the surface. I don't recall much about the weather system but from the looks of the map for the date it was just a weak frontal wave in a zonal flow. If snow were to continue falling at those temperatures for more than a few minutes, it would either change to rain or cool the surface layers to something more hospitable for snow to continue.

I do remember being surprised to see snow when it felt mild and was reading above 40 degrees (this was back in the days before Canada switched to the metric system).

We have melting snow here today with a temperature of about 3 C.

BEASTERLY

thetonynator wrote: »

I think i saw dubai at 30 degrees with a negative DP over the summer, but it could have been a mistake.

But i suppose the snow flake has to be created in temps under 0c in 30 degrees that means it would have to fall from 15000ft.

Plus in humidity that low there would be no precip and even if there was the evaporation resulting from the low humidity means the flake wouldn't last a 100m fall.

thetonynator

BEASTERLY wrote: »

But i suppose the snow flake has to be created in temps under 0c in 30 degrees that means it would have to fall from 15000ft.

Plus in humidity that low there would be no precip and even if there was the evaporation resulting from the low humidity means the flake wouldn't last a 100m fall.

That probably explains why the UAE isnt famous for its July blizzards . .:P

fizzycyst

since humidity is at 100% when dew point=temperature, then I think at 10C if you had 0% humidity that is the top temp you get snow
theoretically I mean!

BEASTERLY

thetonynator wrote: »

That probably explains why the UAE isnt famous for its July blizzards . .:P

LOL:D

jimmy.d

thetonynator wrote: »

I think i saw dubai at 30 degrees with a negative DP over the summer, but it could have been a mistake.

well austrailia had 11" of snow in the middle of summer on 22 of dec

BEASTERLY

jimmy.d wrote: »

well austrailia had 11" of snow in the middle of summer on 22 of dec

At what altitude?

jimmy.d

BEASTERLY wrote: »

At what altitude?

i dont no there was a link to it on here about a week ago

fizzycyst

what part of Austrailia? what temperature?

BEASTERLY

jimmy.d wrote: »

i dont no there was a link to it on here about a week ago

Ah I remember it now, i might be wrong but i think there is ski resorts in the South-East of the country, it could have been up there(down there)

Supercell

The atmosphere though is full of layers. Just because the dp on the ground appears marginal it may not be so higher up.
I am sure there are exterme events where there is a thin lower warm airmass overlaid with a thick cold one and snow can punch though even at surprisingly higher ground temperatures. I'm guess this happens in large continental areas in late spring where there is powerful sun able to heat lower air levels with big cold air masses splashing over occasionally. Just speculating.

thetonynator

jimmy.d wrote: »

well austrailia had 11" of snow in the middle of summer on 22 of dec

It was mainly high altitude ski resorts, which are more likely to have snow that dubai is out in the desert.

although they have an indoor ski resort in dubai with snow machine . . .a giant freezer basically that costs an absolute fortune to run.

BEASTERLY

thetonynator wrote: »

It was mainly high altitude ski resorts, which are more likely to have snow that dubai is out in the desert.

although they have an indoor ski resort in dubai with snow machine . . .a giant freezer basically that costs an absolute fortune to run.

You cant put a price on snow tho:)

jimmy.d

BEASTERLY wrote: »

You cant put a price on snow tho:)

here ya gohttp://www.telegraph.co.uk/news/worldnews/australiaandthepacific/australia/8213932/Wintry-weather-brings-snow-to-Australia-in-midsummer.html

Pangea

I had snow falling at 5.6c today , see the current conditions thread.