minus temp no frost

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flounder

minus temp no frost

Post by flounder » Thu Feb 02, 2012 11:52 pm

Some one please explain this phenomena to me. Temps got down to -2.4c ish but no frost on windscreen or grass as I usually see.
I know it must be to do with relative humidity and stuff, but would like a concise and lucid explanation
ta

billdango

Re: minus temp no frost

Post by billdango » Thu Feb 02, 2012 11:59 pm

flounder wrote:Some one please explain this phenomena to me. Temps got down to -2.4c ish but no frost on windscreen or grass as I usually see.
I know it must be to do with relative humidity and stuff, but would like a concise and lucid explanation
ta
It was the same here in Southampton last night?

_3c and not a hint of frost.

I think the humidity was rather low so that was the reason.

rgds Billdango

GoggleboxUK

Re: minus temp no frost

Post by GoggleboxUK » Fri Feb 03, 2012 12:07 am

If the temp doesn't get as low as the dewpoint you won't get frost because no moisture is formed on surfaces to freeze and turn all sparkly white.

It can be minus 6 but if the dewpoint is -8 then the air is dry and cold rather than wet and cold.

Don't make the mistake of thinking ground frost is frozen surface water, it isn't. It's the dew formed by the condensation process that occurs when the air temperature and the land surface temperature are at odds and condensation occurs then freezes.

I learned that off Stephen the other day so just passing it on. Blame the teacher if I've got it wrong :lol:

flounder

Re: minus temp no frost

Post by flounder » Fri Feb 03, 2012 12:11 am

Right thanks guys, they were the answers I expected. Just wanted clarification icon_thumright

Conifers
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Re: minus temp no frost

Post by Conifers » Fri Feb 03, 2012 12:16 am

Was the soil hard and puddles frozen?

GREVILLE

Re: minus temp no frost

Post by GREVILLE » Fri Feb 03, 2012 12:17 am

Low humidity, low frost. My humidity levels were down to 34% today. Driving home at 11pm tonight no frost to be seen anywhere. My weather station told me -3c and 67% humidity. It's always higher at night but that level is still too low for frost on vehicles. You might see a little on the grass as, holding moisture, it will be more humid at ground level.

flounder

Re: minus temp no frost

Post by flounder » Fri Feb 03, 2012 12:18 am

Conifers wrote:Was the soil hard and puddles frozen?
yes and no because there weren't any puddles

Mr List

Re: minus temp no frost

Post by Mr List » Fri Feb 03, 2012 7:50 am

does the lack of frost make any difference to plant damage at any given temperature
ie
-6 with frost is worse than -6 without (or visa versa)

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The Codfather
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Re: minus temp no frost

Post by The Codfather » Fri Feb 03, 2012 8:04 am

Mr List wrote:does the lack of frost make any difference to plant damage at any given temperature
ie
-6 with frost is worse than -6 without (or visa versa)
I have have had - 6 with frost last night ! :(
AKA - Martin

Wish list - Big Palms or Dicksonia antarctica's but open to anything really.....Cash Waiting !

kata

Re: minus temp no frost

Post by kata » Fri Feb 03, 2012 8:13 am

Wrap up Coddy............ :lol: :lol:

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Dave Brown
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Re: minus temp no frost

Post by Dave Brown » Fri Feb 03, 2012 8:24 am

We get these cold dry NE winds here periodically every late winter and spring. The main problem apart from wind chill factor is the low humidity, which then desicates the ground and plants. I'll be out there dousing the Dicksonia antarctica down as soon as this freeze is over..... provided I'm not under 6 feet of snow that is :lol:
Best regards
Dave
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Roll on summer.....
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Exotic Life

Re: minus temp no frost

Post by Exotic Life » Fri Feb 03, 2012 10:25 am

No very humid here as well with the lowest point yesterday with just below 30%. It's swinging between the 30-40% since the cold started. Lows between the -5/-10 and windchills till -20C. Now I do know again why I hate winter...

But at least no frozen car windows as well. :)

cordyman

Re: minus temp no frost

Post by cordyman » Sat Feb 04, 2012 2:21 pm

Mr List wrote:does the lack of frost make any difference to plant damage at any given temperature
ie
-6 with frost is worse than -6 without (or visa versa)
i'd like to know this too!


I had over -4*c last night and ground didnt have a trace of frost, but car did have a little frost on the windscreen, but side windows were all clear.

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