On Thursday, 5 February 2015 14:23:29 UTC, wrote:
"Alan [Guildford]" wrote in message
...
On Thursday, 5 February 2015 13:23:20 UTC,
wrote:
"Alan [Guildford]" wrote in message
...
On Thursday, 5 February 2015 12:35:48 UTC,
wrote:
Having had a week of not so bitter weather with temps around 5C I was
expecting it to be colder today. So why, with 850 hPa indicating -8C
here, sub 528 dam, is it 6C and raining in the showers?

Dave, S.Essex

That is certainly possible with a dry adiabatic lapse rate and/or
instability at the surface.

Except it is not. The Ekofisk sounding in the North Sea is DALR up to 900
hPa only. The wet-bulb freezing level is at 300 metres asl, meaning snow
down to 100 metres asl unless heavy. The surface temperature over the sea
at
Ekofisk was around 5C.


So assuming the 850mb level is approx 1500 metres asl with a temperature
of -8C, and the surface temperature is say +5C thus giving a difference of
13C, and a lapse rate of approx 0.85C / 100metres.

This is somewhere between the dry and saturated lapse rates so I was
guessing with the dew point being around 0C [according to the GFS] that
at least some of the lapse rate would be at the dry end of the scale?


Which is what I said, DALR up to 900 hPa level.

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

Sorry I think I misunderstood the "Except it is not" in the original reply.

Cheers

Alan