Apolgies from a newbie if this turns out to be an old chestnut.
I have noticed this before in general - but in particular up here
(N.Yorks) in the last few days.I imagine there is a scientific name
for the phenomenon - which I hope someone will tell me.But more
generally I am hoping that someone will explain how/why it happens.
Layman's observations as follows.When I get up and take dogs out just
before dawn (c 7am now) I notice just traces of frost but nothing much
An hour later after it is light- I notice the frost is much more
intense - white over - and ice on the roads.
I would be most grateful for an explanation of why this happens and
what it is called.Many thanks.

Hawkeye

"Hawkeye23" wrote in message
...
Apolgies from a newbie if this turns out to be an old chestnut.
I have noticed this before in general - but in particular up here
(N.Yorks) in the last few days.I imagine there is a scientific name
for the phenomenon - which I hope someone will tell me.But more
generally I am hoping that someone will explain how/why it happens.
Layman's observations as follows.When I get up and take dogs out just
before dawn (c 7am now) I notice just traces of frost but nothing much
An hour later after it is light- I notice the frost is much more
intense - white over - and ice on the roads.
I would be most grateful for an explanation of why this happens and
what it is called.Many thanks.

Hawkeye
-------------------
Welcome! Someone did explain it on here once but I can't remember the
answer. I would guess that if the temperature is dropping at a certain rate
and the temperature is near zero there is a lag before the sun has any
strength, especially at this time of year, and it continues to fall for a
while.
Dave

On Nov 29, 10:00*pm, "Dave Cornwell"
wrote:
"Hawkeye23" wrote in message


just before dawn I notice just traces of frost but nothing much
An hour later after it is light- I notice the frost is much more
intense - white over - and ice on the roads.
I would be most grateful for an explanation of why this happens and
what it is called.

. I would guess that if the temperature is dropping at a certain rate
and the temperature is near zero there is a lag before the sun has any
strength, especially at this time of year, and it continues to fall for a
while.

You mean it is a miracle that these thing endeavour to occur on time
no matter how early it gets early?

It isn't that -for sunlight would have degree of hesitancy, day to
day. And it would be so unlikely to occur as sequentially as described
as to be impossible.

2 in 365 is rather a remote chance but every day there is this
phenomenon it occurs just after dawn?

It has to practical and logical as well as obeying the physics of the
school syllabus.

On Sat, 29 Nov 2008 17:27:05 -0800 (PST), Weatherlawyer
wrote:

On Nov 29, 10:00*pm, "Dave Cornwell"
wrote:
"Hawkeye23" wrote in message


just before dawn I notice just traces of frost but nothing much
An hour later after it is light- I notice the frost is much more
intense - white over - and ice on the roads.
I would be most grateful for an explanation of why this happens and
what it is called.

. I would guess that if the temperature is dropping at a certain rate
and the temperature is near zero there is a lag before the sun has any
strength, especially at this time of year, and it continues to fall for a
while.

You mean it is a miracle that these thing endeavour to occur on time
no matter how early it gets early?

It isn't that -for sunlight would have degree of hesitancy, day to
day. And it would be so unlikely to occur as sequentially as described
as to be impossible.

2 in 365 is rather a remote chance but every day there is this
phenomenon it occurs just after dawn?

It has to practical and logical as well as obeying the physics of the
school syllabus.
Ya Wot

jeff

On 29 Nov, 18:59, Hawkeye23 wrote:
Apolgies from a newbie if this turns out to be an old chestnut.
I have noticed this before in general - but in particular up here
(N.Yorks) in the last few days.I imagine there is a scientific name
for the phenomenon - which I hope someone will tell me.But more
generally I am hoping that someone will explain how/why it happens.
Layman's observations as follows.When I get up and take dogs out just
before dawn (c 7am now) I notice just traces of frost but nothing much
An hour later after it is light- I notice the frost is much more
intense - white over - and ice on the roads.
I would be most grateful for an explanation of why this happens and
what it is called.Many thanks.

Dear Mr Hawkeye,

Further to Dave Cornwell's explanation, there is the added input of
the westerly katabatic flow in this part of NE England.
You do not say where you are situated but if you are in hill country
and above the valley floor you could be experiencing mixing of warmer
upper air.
During clear, calm periods, the cold downflow from the Pennine slopes
begins around sunset and stops around sunrise. Our lowest temperatures
are often during the calm periods at these two times. The rest of the
night is often quite breezy, mixing the warmer air aloft.
A good example was last night here in Copley. The Lead Mill area in
the valley was not disturbed by the mixing and fell to -7.0C while the
upper village had two minima times with -2.1C just after sunset and
-2.7C after sunrise. The wind fell calm again at 10Z with a consequent
drop from -0.5C to -2.0C in full sun.

Hope that helps.

Ken