I was at work across the valley and noted minimum overnight was -5.6C
as against the one here ( -5.1C) and also noted Hugh at Evershot got
down to -7.4 ( I think).
However, I looked at a graph of the outside temperature and noted that
down here it is truly plunging ( max 0.7C) since 1500hrs compared
with yesterday- so am wondering if tonight will be colder still.
And the house has warmed up to 16C so it is actually reasonably cosy.
In my bedroom (3rd storey) it is 11C

R

On Tue, 06 Jan 2009 19:07:53 +0000, Robin Nicholson
wrote:

However, I looked at a graph of the outside temperature and noted that
down here it is truly plunging ( max 0.7C) since 1500hrs compared
with yesterday- so am wondering if tonight will be colder still.

Down to -5.7C at 2029 but without any apparent cloud cover has shot
'up' to -5.3 in 30 minutes - which is odd


R

"Robin Nicholson" wrote in
message ...
On Tue, 06 Jan 2009 19:07:53 +0000, Robin Nicholson
wrote:

However, I looked at a graph of the outside temperature and noted that
down here it is truly plunging ( max 0.7C) since 1500hrs compared
with yesterday- so am wondering if tonight will be colder still.

Down to -5.7C at 2029 but without any apparent cloud cover has shot
'up' to -5.3 in 30 minutes - which is odd

A slight (almost imperceptible?) increase in windspeed I would
imagine may be all that's required to stir up the coolest air near
the ground with slightly 'warmer' air aloft.
--
Col

Bolton, Lancashire
160m asl

"Col" wrote in message
...

"Robin Nicholson" wrote in
message ...
On Tue, 06 Jan 2009 19:07:53 +0000, Robin Nicholson
wrote:

However, I looked at a graph of the outside temperature and noted that
down here it is truly plunging ( max 0.7C) since 1500hrs compared
with yesterday- so am wondering if tonight will be colder still.

Down to -5.7C at 2029 but without any apparent cloud cover has shot
'up' to -5.3 in 30 minutes - which is odd

A slight (almost imperceptible?) increase in windspeed I would
imagine may be all that's required to stir up the coolest air near
the ground with slightly 'warmer' air aloft.
--
Col

Bolton, Lancashire
160m asl

A shift in wind direction (even without a change in the speed) will also
do the job, depending on the types of surface over which the wind
travels before reaching the Stevenson screen.

During my very long stint at Middle Wallop, I noticed that after dark
on 'good' radiation nights (like tonight), any backing of the light wind
through 315 degrees (NW) would send the temperature down by 2
whole degrees celsius in a matter of minutes as the drift, previously
off an area of concrete, changed to wafting over a large expanse of
colder grass. Most of that 2 degree drop would recover if the wind
veered again but as the night wore on, the effect tended to lessen a
little.

I must be a slow learner because it took me a good few years of
night shifts before I cottoned on to this subtle local effect.

Presumably, this phenomenon is still happening there.

Nigel

On Tue, 6 Jan 2009 21:09:45 -0000, "Col"
wrote:


A slight (almost imperceptible?) increase in windspeed I would
imagine may be all that's required to stir up the coolest air near
the ground with slightly 'warmer' air aloft.

Useful! After that rise it has descended lower and now reads -6.9C

I checked back a few days using the graphs and noted that on the three
recent cold nights it also wobbled around a bit and was never a
straight line. In fact,it is showing another slight increase as I
write. The anenometer has shown just a tad of movement, not that I
have been out watching mind you.

R