Ice question

[Welsh wheels]

Am I right in thinking that ice can't form unless the temperature is below freezing? Or is it more complicated than that?

 

[T.M.H.N.E.T]

Depends on salting too, saline solutions freeze at lower temps

 

[freiston]

A quick google suggests that water can freeze even where the "dry bulb" temperature is above 0° C - as long as the "wet bulb" temperature is below 0° C.

 

[PK99]

the water that is freezing must be at/below 0C.

but ground frost can form when measured air temp 6ft above ground is above zero.

and black ice can form when ambient temps are above zero. I was caught out once in a very cold spell. while in b&q , temp rose and there was a brief rain shower. road surface was below zero and sheet black ice formed on un gritted side roads, as i found out when I pirouetted on turning into a side road.

 

[Slick]

Most modern cars will now give a frost warning at 3C.

 

[Drago]

Indeed. At 3°C you risk finding ice in little microclimates, usually dips or shaded areas.

 

[Pale Rider]

Whether there's black ice for cycling is hard to judge.

Earlier this year after some nasty frosts we had a few days - and nights - of three or four degrees, but the black ice was still there.

Seems to me once formed, ice on the ground takes a surprisingly long time to thaw.

 

[jefmcg]

As a general rule in life, everything is more complicated than that, where that is what you learned in school.

The met office is showing this warning map for now,

And for tomorrow ...

The southerly ice warning is from 4-11am tomorrow, and the Scottish is from now until midday.

 

[jefmcg]

[QUOTE 5073882, member: 9609"]I understand what Yellow Snow is but what is "Amber Snow" ? is it a dietary thing ?[/QUOTE]
Answer in the spirit of the question: dehydration

Actual answer from met office:

 

[raleighnut]

The met office is showing this warning map for now,

View attachment 386720

And for tomorrow ...

View attachment 386721

The southerly ice warning is from 4-11am tomorrow, and the Scottish is from now until midday.

View: https://youtu.be/TLIppgE45wM

 

[Illaveago]

On some TV documentaries they have shown that pure water can remain a liquid way, way below zero whilst in a container, but once you tap it will freeze solid instantly.

 

[jefmcg]

On some TV documentaries they have shown that pure water can remain a liquid way, way below zero whilst in a container, but once you tap it will freeze solid instantly.

This was the subject of a podcast I listened to on Friday. It's impurities that starts the crystals forming.

View: https://www.youtube.com/watch?v=U8HmyLwcYnw


(there's a good reason they use a horse, if you listen to the beginning of the podcast)

 

[jefmcg]

In the same way that the particles from burning coal and wood, caused smogs.

And (listen to the podcast) bacteria cause and travels by snow. Scientists believe there is a bacterium at the centre of every snowflake!

You can easily do something like the above ice experiment with superheated water. Just microwave a cup of water for a couple of minutes - until it's super hot and then some. It usually won't boil. Take it out and standing well clear, drop a teabag or instant coffee in it. If you have done it right, the water will start boiling in the cup, and bubble out. Burns and steam burns are a real risk, so proceed with caution.

 

[Racing roadkill]

I don’t trust the Met office as far as I can throw them. However, on the premise that even a stopped Clock is right twice a day, I’d hazard a guess that the next couple of days, may be ‘sub optimal’ riding conditions. Ice doesn’t form on roads that are treated in such a way as to modify any water to depress its freezing point, but if it’s very cold ( less than -5 degrees Celsius) I’d er on the side of caution, and not use a bike ( Trike and quad would still be fair game), and use another form of transport.

 

[Tim Hall]

In the same way that the particles from burning coal and wood, caused smogs.

Con trails from aircraft too, according to my physics teacher way back when. Of course we all know it's a whole lot more sinister than that.