Checking out the 12z runs:

http://www.wzkarten.de/pics/Rtavn1923.png

kicks off the cold big time.

I have the daily weather charts for the 62/63 Winter and a ridge from
Spain joined forces with a Scandinavian high, a front became retrograde
over the North Sea and the rest as they say is history!

Hmm ;-))
--
James Brown

In article ,
James Brown writes:
Checking out the 12z runs:

http://www.wzkarten.de/pics/Rtavn1923.png

kicks off the cold big time.

I have the daily weather charts for the 62/63 Winter and a ridge from
Spain joined forces with a Scandinavian high, a front became retrograde
over the North Sea and the rest as they say is history!

Hmm ;-))

The GFS Ensemble 850mb temps for London are now looking decidedly
chilly:

http://91.121.93.17/pics/MT8_London_ens.png
--
John Hall "[It was] so steep that at intervals the street broke into steps,
like a person breaking into giggles or hiccups, and then resumed
its sober climb, until it had another fit of steps."
Ursula K Le Guin "The Beginning Place"

In article ,
John Hall writes:
In article ,
James Brown writes:
Checking out the 12z runs:

http://www.wzkarten.de/pics/Rtavn1923.png

kicks off the cold big time.

I have the daily weather charts for the 62/63 Winter and a ridge from
Spain joined forces with a Scandinavian high, a front became retrograde
over the North Sea and the rest as they say is history!

Hmm ;-))

The GFS Ensemble 850mb temps for London are now looking decidedly
chilly:

http://91.121.93.17/pics/MT8_London_ens.png


The 12:00 ECMWF run is now out. The operational run wants to direct the
coldest air from NE to SW just to the east and south of us, but as
that's at days 9 and 10 it might easily change.
--
John Hall "[It was] so steep that at intervals the street broke into steps,
like a person breaking into giggles or hiccups, and then resumed
its sober climb, until it had another fit of steps."
Ursula K Le Guin "The Beginning Place"

On 2009-12-07, John Hall wrote:


The 12:00 ECMWF run is now out. The operational run wants to direct the
coldest air from NE to SW just to the east and south of us, but as
that's at days 9 and 10 it might easily change.


How does 850mb temp correspond with surface temp at this time of year?
is -5 @ 850mb 0C at the surface?
--
comp.john

"comp.john" wrote in message
...

How does 850mb temp correspond with surface temp at this time of year?
is -5 @ 850mb 0C at the surface?
--
comp.john

It's not really the best guide for surface temperatures as the boundary
layer conditions at this time of year can heavily modify a direct adiabatic
translation. However, to give you some idea, when 850mb temperatures were
around -4 around a week ago daytime surface temperatures were in the +4 to
+6 ballpark.

Jon.

On 7 Dec, 19:35, "comp.john" wrote:
On 2009-12-07, John Hall wrote:



The 12:00 ECMWF run is now out. The operational run wants to direct the
coldest air from NE to SW just to the east and south of us, but as
that's at days 9 and 10 it might easily change.

How does 850mb temp correspond with surface temp at this time of year?
is -5 @ 850mb 0C at the surface?
--
comp.john

One of the experts on here will probably give you a much better
answers, but assuming no temperature inversion, typically -5 @ 850mb
would equate to about +4 degrees at sea level, for air which has come
of the ocean. If the air comes direct from the continent then things
are more complex, there’s likely to be an inversion this time of year,
but if the air is bone dry, in theory it could be as high as +10C, but
highly unlikey.

"Alan" wrote in message
...
On 7 Dec, 19:35, "comp.john" wrote:
On 2009-12-07, John Hall wrote:



The 12:00 ECMWF run is now out. The operational run wants to direct the
coldest air from NE to SW just to the east and south of us, but as
that's at days 9 and 10 it might easily change.

How does 850mb temp correspond with surface temp at this time of year?
is -5 @ 850mb 0C at the surface?
--
comp.john

One of the experts on here will probably give you a much better
answers, but assuming no temperature inversion, typically -5 @ 850mb
would equate to about +4 degrees at sea level, for air which has come
of the ocean. If the air comes direct from the continent then things
are more complex, there’s likely to be an inversion this time of year,
but if the air is bone dry, in theory it could be as high as +10C, but
highly unlikey.
============

-5C is normally cold enough for rain to turn to snow at sea level and for
definite snow above 200 metres.
-7C is cold enough for snow at all levels. But as Jon and John have said it
is a lot more complex than that really as it depends on the actual
temperature structure below that level.

Will
--

On 2009-12-07, Will Hand wrote:

-5C is normally cold enough for rain to turn to snow at sea level and for
definite snow above 200 metres.
-7C is cold enough for snow at all levels. But as Jon and John have said it
is a lot more complex than that really as it depends on the actual
temperature structure below that level.

Thanks everyone for clarifying.
--
comp.john

On 2009-12-07, John Hall wrote:

The GFS Ensemble 850mb temps for London are now looking decidedly
chilly:

http://91.121.93.17/pics/MT8_London_ens.png

What do the coloured P numbers mean down the left side of the chart?
--
comp.john

"comp.john" wrote in message
...
On 2009-12-07, John Hall wrote:

The GFS Ensemble 850mb temps for London are now looking decidedly
chilly:

http://91.121.93.17/pics/MT8_London_ens.png

What do the coloured P numbers mean down the left side of the chart?
--
comp.john


.... tags identifying the individual perturbation outcome depicted on
the composite plume. P=0 is the first perturbation, P=1 is the second
and so on. The colours match the individual (thin) lines on the chart.
Useful if you're trying to identify clustering of the members of the
plume-set.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023