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

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.

wrote in message
...
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?


Long fetch off a super warm North Sea below 850 hPa melting the snowflakes
aloft. Sadly for you SE folk the days of sig. snow at low level are getting
rarer, unless the North Sea cools down more again in winters, it will remain
thus. At altitude, in places like Luton, snow will continue to occur
regularly but it will not be bitter. You are quickly becoming like the south
coast whereby the only time you will get sig. snow is if the 1000-500 hPa
thickness falls below 516 DAM, or you get a more continental air fetch or a
"special" synoptic setup like a slow moving front with a fetch off colder
land. Snow lovers need to gain latitude or altitude, preferably both.

Sorry :-(

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

"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.

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

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.

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

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?

"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)
---------------------------------------------

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

In message , Eskimo Will
writes

wrote in message
...
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?


Long fetch off a super warm North Sea below 850 hPa melting the
snowflakes aloft. Sadly for you SE folk the days of sig. snow at low
level are getting rarer, unless the North Sea cools down more again in
winters, it will remain thus. At altitude, in places like Luton, snow
will continue to occur regularly but it will not be bitter. You are
quickly becoming like the south coast whereby the only time you will
get sig. snow is if the 1000-500 hPa thickness falls below 516 DAM, or
you get a more continental air fetch or a "special" synoptic setup like
a slow moving front with a fetch off colder land. Snow lovers need to
gain latitude or altitude, preferably both.

Though with an easterly the sea track will be very short, so we should
still get snow in those situations. However they've been very rare in
recent years.

Interestingly, we now seem to get more snow in Surrey than they do in
Essex, which never used to be the case. Presumably that's because the
sir that has been warmed close to the surface by crossing the North Sea
has had nore chance to cool down again.

Of course in prolonged cold spells, the North Sea will become colder and
SE England will get more snow, as illustrated in 2009-10 and December
2010. So I'm not that pessimistic.
--
I'm not paid to implement the recognition of irony.
(Taken, with the author's permission, from a LiveJournal post)

On Thursday, 5 February 2015 13:13:18 UTC, wrote:
wrote in message
...
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?


Long fetch off a super warm North Sea below 850 hPa melting the snowflakes
aloft. Sadly for you SE folk the days of sig. snow at low level are getting
rarer, unless the North Sea cools down more again in winters, it will remain
thus. At altitude, in places like Luton, snow will continue to occur
regularly but it will not be bitter. You are quickly becoming like the south
coast whereby the only time you will get sig. snow is if the 1000-500 hPa
thickness falls below 516 DAM, or you get a more continental air fetch or a
"special" synoptic setup like a slow moving front with a fetch off colder
land. Snow lovers need to gain latitude or altitude, preferably both.

Sorry :-(

Will
--
Any idea on frequency, Will? I think December 2010 was considered a once in 100 year event, whereas perhaps in the 1960s, it could be considered a once in 15 year event.

Have you seen the snowfall in Villablino, Spain. Well over a metre. The location is at over 1,000m

https://twitter.com/JaimeDobleVFM/st...299072/photo/1

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In message ,
Scott W writes
On Thursday, 5 February 2015 13:13:18 UTC, wrote:
wrote in message
...
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?


Long fetch off a super warm North Sea below 850 hPa melting the snowflakes
aloft. Sadly for you SE folk the days of sig. snow at low level are getting
rarer, unless the North Sea cools down more again in winters, it will remain
thus. At altitude, in places like Luton, snow will continue to occur
regularly but it will not be bitter. You are quickly becoming like the south
coast whereby the only time you will get sig. snow is if the 1000-500 hPa
thickness falls below 516 DAM, or you get a more continental air fetch or a
"special" synoptic setup like a slow moving front with a fetch off colder
land. Snow lovers need to gain latitude or altitude, preferably both.

Any idea on frequency, Will? I think December 2010 was considered a
once in 100 year event, whereas perhaps in the 1960s, it could be
considered a once in 15 year event.

I'm not Will, but since it was the coldest December since 1890 it could
hardly have been a once in 15 year event at any time during the 20th
century. Otherwise months that cold would have been more frequent. There
have only been eight sub-zero Decembers in the 350-odd years of the CET:
1676, 1788, 1796, 1874, 1878, 1890, 2010. So sub-zero Decembers might
have been a once in 15 year event in the late 1800s. Even before that,
though, there were a couple of very long gaps without any.


Have you seen the snowfall in Villablino, Spain. Well over a metre. The
location is at over 1,000m

https://twitter.com/JaimeDobleVFM/st...299072/photo/1


Impressive. There was a brief item on the BBC 1pm news about the snow in
northern Spain, but the footage they showed was of snow not nearly as
deep as that.

It looks as though Greece could have some exceptionally cold weather
next week.
--
I'm not paid to implement the recognition of irony.
(Taken, with the author's permission, from a LiveJournal post)