It appears that there is a classic negative AO and NAO just now.

Polar vortex about to weaken?

Can't say, but it is whetting the appetite of the coldies.

Try this link

http://www.markvoganweather.com/2017...-ahead-for-uk/

Len

On 27/11/2017 21:36, Len Wood wrote:
It appears that there is a classic negative AO and NAO just now.

Polar vortex about to weaken?

Can't say, but it is whetting the appetite of the coldies.

Try this link

http://www.markvoganweather.com/2017...-ahead-for-uk/

Len


Its always sensible to treat any meteorology over Greenland as a
singularity (only 1 met station at high elevation surrounded by ice) as
the seas around Greenland show nothing majorly unusual, I'll treat that
with a dollop of brine.

On 28/11/2017 09:27, N_Cook wrote:
On 27/11/2017 21:36, Len Wood wrote:
It appears that there is a classic negative AO and NAO just now.

Polar vortex about to weaken?

Can't say, but it is whetting the appetite of the coldies.

Try this link

http://www.markvoganweather.com/2017...-ahead-for-uk/


Len


Its always sensible to treat any meteorology over Greenland as a
singularity (only 1 met station at high elevation surrounded by ice) as
the seas around Greenland show nothing majorly unusual, I'll treat that
with a dollop of brine.

Or put it another way, how many people would be living in Scotland if
this weather station
http://cairngormweather.eps.hw.ac.uk/current.htm
was fully representative of the whole of Scotland , except for those
people living right on the coast

On Tuesday, November 28, 2017 at 4:01:53 PM UTC, N_Cook wrote:
On 28/11/2017 09:27, N_Cook wrote:
On 27/11/2017 21:36, Len Wood wrote:
It appears that there is a classic negative AO and NAO just now.

Polar vortex about to weaken?

Can't say, but it is whetting the appetite of the coldies.

Try this link

http://www.markvoganweather.com/2017...-ahead-for-uk/


Len


Its always sensible to treat any meteorology over Greenland as a
singularity (only 1 met station at high elevation surrounded by ice) as
the seas around Greenland show nothing majorly unusual, I'll treat that
with a dollop of brine.

Or put it another way, how many people would be living in Scotland if
this weather station
http://cairngormweather.eps.hw.ac.uk/current.htm
was fully representative of the whole of Scotland , except for those
people living right on the coast

I don't believe the graphics are relying on one surface station.
We are talking about a warm air mass arriving over Greenland due the arrangement of circumpolar waves.
Have you looked at the link?
Do you understand how a jet stream chart is constructed?

Len

Yes, there's no question of Greenland warming with geopotential heights rising strongly again, as they will again over Alaska after current temporary relaxation that is allowing unseasonal warming over much of North America into then first week of December.

A strong wave 3 pattern looks like developing with durable blocking especially over Alaska and Greenland and it ought to be more or less locked in place for at least a couple of weeks and potentially right through December. The upshot is troughing / cold towards Europe and across eastern North America held in place for much of the month.

I would say that the stratospheric polar vortex is being displaced (towards Eurasia) rather than weakened particularly yet, though.

Stephen.

"Len Wood" wrote in message
...
It appears that there is a classic negative AO and NAO just now.

Polar vortex about to weaken?

Can't say, but it is whetting the appetite of the coldies.

Try this link

http://www.markvoganweather.com/2017...-ahead-for-uk/

Len

The surface temperature (screen) over the Greenland ice cap is dominated by
radiation. Provided the sky is clear, it is able to fall to very low values.
If cloud (or humid air) comes over, the outgoing LW radiation will be cut
and the surface temperature will rise, the same effect observable with grass
min over snow (or, to a lesse extent, grass) in the UK. Thus the subject
headline is, while factually accurate, rather misleading. There was
undoubtably warm air advection occurring over Greenland between the 24th and
28th, and using the soundings from the Geosummit station (04417), the
thickness in the layer 700 (near the surface) and 500 hpa rose from 2357 gpm
to 2526 gpm, and converting this to the mean temperature in that layer, the
mean temperature rose from -34.0 to -16.8C, an increase of 17C. The main
reason for the 40C rise was the arrival of the moist/cloudy air associated
with this warm advection.

--
Bernard Burton

Satellite images and weather data for Wokingham at:
www.woksat.info/wwp.html



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