0705

Overnight min +0.0 Current temperature +0.3 deg C.
Just too much wind overnight (1-3 knots) for lower temperatures.
Probably -2 or -3 deg C in the well known frosty spots in the South Hams or in
the Teign Valley.
Lovely sunrise again over Lyme Bay, though a tad more murky than yesterday.

Will.
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Overnight min +0.0 Current temperature +0.3 deg C.
Just too much wind overnight (1-3 knots) for lower temperatures.
Probably -2 or -3 deg C in the well known frosty spots in the South Hams or in
the Teign Valley.

Will,

It went down to -0.9C in the Otter Valley last night though for most of
the night the temperature fluctuated between 1 & 3C as there was a
slight breeze about, this breeze finally gave up during the latter half
of the night allowing the temperature to fall below freezing.
________________
Nick G
Otter Valley, Devon
83 amsl

Will Hand wrote:
0705

Overnight min +0.0 Current temperature +0.3 deg C.

Er, forgive me for the intrusion, but the last time I did this sort of
thing 0.0 C was a frost. Water freezes at zero (given the right
conditions).

If 0.0 is not now recognised as a frost, then I demand that 20 years of
Open Road verification figures be re-assessed in the forecasters favour.

On 2 Nov 2006 02:21:03 -0800, wrote in
roups.com

Will Hand wrote:
0705

Overnight min +0.0 Current temperature +0.3 deg C.

Er, forgive me for the intrusion, but the last time I did this sort of
thing 0.0 C was a frost. Water freezes at zero (given the right
conditions).

If 0.0 is not now recognised as a frost, then I demand that 20 years of
Open Road verification figures be re-assessed in the forecasters favour.

As far as I'm aware a temp of 0.0C has *never* been recognised as a frost.

--
Mike Tullett - Coleraine 55.13°N 6.69°W posted 02/11/2006 12:30:33 GMT

On Thu, 2 Nov 2006 12:30:33 +0000, Mike Tullett wrote in


If 0.0 is not now recognised as a frost, then I demand that 20 years of
Open Road verification figures be re-assessed in the forecasters favour.

As far as I'm aware a temp of 0.0C has *never* been recognised as a frost.

p.s. water has to go below zero, sometimes by a long way, for ice to form.

--
Mike Tullett - Coleraine 55.13°N 6.69°W posted 02/11/2006 12:31:43 GMT

Er, forgive me for the intrusion, but the last time I did this sort of
thing 0.0 C was a frost. Water freezes at zero (given the right
conditions).

Hmmmm, not quite. To calibrate a thermometer to 0C you immerse it in
water, of which it has formed from melted ice (which must still be
present in reasonable enough quantity to ensure a uniform temperature
throughout the water).

Therefore, it could be said that 0C is the point that ice turns to
water and -0.1C is the point at which water turns to ice.

So to be a true air frost the temperature must be at -0.1C or lower.
_________________
Nick G
Otter Valley, Devon
83 m amsl

Felly sgrifennodd Nick G :
Hmmmm, not quite. To calibrate a thermometer to 0C you immerse it in
water, of which it has formed from melted ice (which must still be
present in reasonable enough quantity to ensure a uniform temperature
throughout the water).

Therefore, it could be said that 0C is the point that ice turns to
water

I'm following you so far...

and -0.1C is the point at which water turns to ice.

So to be a true air frost the temperature must be at -0.1C or lower.

But now I've lost you. What happens at -0.001 for example?

As far as I'm concerned, if my thermometer has a resolution of 0.1C (and
assuming it's accurate), a temperature of 0.0C may or may not be a
frost, depending on which side of 0.0C it is (e.g. is it +0.045C or
-0.045C). I don't really care that much. Quibbling over it is pointless.

Adrian
--
Adrian Shaw ais@
Adran Cyfrifiadureg, Prifysgol Cymru, aber.
Aberystwyth, Ceredigion, Cymru ac.
http://users.aber.ac.uk/ais/weather/ uk

But now I've lost you. What happens at -0.001 for example?

As far as I'm concerned, if my thermometer has a resolution of 0.1C (and
assuming it's accurate), a temperature of 0.0C may or may not be a
frost, depending on which side of 0.0C it is (e.g. is it +0.045C or
-0.045C). I don't really care that much. Quibbling over it is pointless.

You are right, but the measurement of atmospheric temperature is
usually taken to a resolution 0.1C, therefore a standard has to be used
and -0.1C or below is the point at which it is a frost and not 0.0C.

If you want to take it all to its logical conclusion then 'Quibbling
over' the measurement of temperature/time/mass/distance/velocity is
meaningless because at what point is it exactly, say 10:00am, therefore
you could hypothesise that 10:00 am doesn't actually exist as it is
either 'to' or 'past' 10:00am and there is no point in time when it is
actually 10:00am. It's an infinity thing.
___________________
Nick G
Otter Valley, Devon
83 m amsl

Mike Tullett wrote:
On Thu, 2 Nov 2006 12:30:33 +0000, Mike Tullett wrote in


If 0.0 is not now recognised as a frost, then I demand that 20 years of
Open Road verification figures be re-assessed in the forecasters favour.

As far as I'm aware a temp of 0.0C has *never* been recognised as a frost.


Perhaps you would care to convey this information to the authorities
that grit your roads.

On 2 Nov 2006 06:21:26 -0800, wrote in
ups.com

As far as I'm aware a temp of 0.0C has *never* been recognised as a frost.

Perhaps you would care to convey this information to the authorities
that grit your roads.

0C is the melting point of ice, not the freezing point of water. Thus for
water to freeze it must be colder than the melting point of ice i.e. below
0C.

Quote "When the temperature as measured in this way falls below 0.0 deg C,
then an AIR FROST is recorded" from Martin Rowleys FAQ site:

http://homepage.ntlworld.com/booty.w...Q/2A.htm#2A.14

--
Mike Tullett - Coleraine 55.13°N 6.69°W posted 02/11/2006 14:46:38 GMT