:-)
http://acdb-ext.gsfc.nasa.gov/Data_s...2012_merra.pdf

Mean zonal wind has decreased markedly at 60N.

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

"Eskimo Will" wrote in message
...
:-)
http://acdb-ext.gsfc.nasa.gov/Data_s...2012_merra.pdf

Mean zonal wind has decreased markedly at 60N.

Merry Christmas everyone :-)

Will,
Your link shows the zonal wind. The stratwarm is shown he
http://acdb-ext.gsfc.nasa.gov/Data_s...2012_merra.pdf

But if it is going to bring us cold weather surely the stratwarm has to
happen at the right longitude. What is the longitude for the stratwarms that
have brought us cold? How can we tell where this stratwarm is happening?

Cheers, Alastair.

In article ,
Eskimo Will writes:
:-)
http://acdb-ext.gsfc.nasa.gov/Data_s...tdata/annual/m
erra/u60n_150_2012_merra.pdf

Mean zonal wind has decreased markedly at 60N.

I take it that the mauvish line is the one that is relevant? That does
seem to have taken a very marked dip in recent days.
--
John Hall

"Whenever people agree with me I always feel I must be wrong."
Oscar Wilde

On Wed, 26 Dec 2012 10:39:35 -0000, "Alastair McDonald"
wrote:
But if it is going to bring us cold weather surely the stratwarm
has to
happen at the right longitude.

It's a bit more complex than that. A disruption to the zonal flow
anywhere in our hemisphere will have a downstream effect right round
the globe - dependent on the strength and the orientation of the
disruption. I doubt there is a 'right' longitude.

--
Freddie
Bayston Hill
Shropshire
102m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/#!/BaystonHillWx*for hourly reports*

"Freddie" wrote in message
.net...
On Wed, 26 Dec 2012 10:39:35 -0000, "Alastair McDonald"
wrote:
But if it is going to bring us cold weather surely the stratwarm
has to
happen at the right longitude.

It's a bit more complex than that. A disruption to the zonal flow anywhere
in our hemisphere will have a downstream effect right round the globe -
dependent on the strength and the orientation of the disruption. I doubt
there is a 'right' longitude.

Yes, but the net the zonal flow must always be zero otherwise all the air
would gather at one longitude. So what happens is that the flow is a closed
loop, but becomes more wavy as the stratwarm forms. To a first
approximation, we will get cold weather if a wave/loop comes south over us,
so the stratwarm has to form at 180 degrees west to produce the warm
northern loop. In fact for us to get snow we need the southern loop of polar
air to form over Russia and expand westward. I don't think a stratwarm
centred on Moscow would bring us snow.

Cheers, Alastair.

On Wednesday, December 26, 2012 10:39:35 AM UTC, Alastair wrote:
"Eskimo Will" wrote in message

...

:-)

http://acdb-ext.gsfc.nasa.gov/Data_s...2012_merra.pdf



Mean zonal wind has decreased markedly at 60N.



Merry Christmas everyone :-)



Will,

Your link shows the zonal wind. The stratwarm is shown he

http://acdb-ext.gsfc.nasa.gov/Data_s...2012_merra.pdf



But if it is going to bring us cold weather surely the stratwarm has to

happen at the right longitude. What is the longitude for the stratwarms that

have brought us cold? How can we tell where this stratwarm is happening?



Cheers, Alastair.

It's really not difficult to do the research guys. The last minor SSW event (around 13th Dec) produced precisely *no* discernible effect on the UK weather.........not quite what some on here predicted. A minor event is currently happening. They quite often do during the boreal winter. The forecast is for the zonal wind at 10hpa to *increase* and certainly not to decrease, or to reverse. Thus the chances of this event affecting the surface would be extremely remote. The Meto 6+ day forecast implies they think exactly the same as I do.

http://wekuw.met.fu-berlin.de/~Aktue...w/wdiag/ts.php

You can see the reversal caused by the SSW of mid-dec can easily be seen in the 10hpa winds.

It's not hard to do the research on thisand learn. We've had people inferring that every SSW at all magnitudes will affect the UK weather in some way. That's plain daft. There is no research that says that* and it's just the butterfly's wings and the Atlantic hurricane stuff yet again. Basically, just ignore them. They know not what they say. *))

*All I say is show us the research that shows that they do. It's not much to ask.

On Wed, 26 Dec 2012 12:22:18 -0000, "Alastair McDonald"
wrote:
Yes, but the net the zonal flow must always be zero otherwise all
the air
would gather at one longitude.
That's not strictly true, as you are not taking into account vertical
motion.

I don't think a stratwarm
centred on Moscow would bring us snow.
In my earlier reply, I was actually going to add that there are
probably _bad_ places for it to occur - but when I wrote the sentence
it looked a bit patronising, so I deleted it. I agree with what you
are saying up to a point, but as I said before I think you are over
simplifying the dynamics.

--
Freddie
Bayston Hill
Shropshire
102m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/#!/BaystonHillWx*for hourly reports*

"Freddie" wrote in message
.net...
On Wed, 26 Dec 2012 12:22:18 -0000, "Alastair McDonald"
wrote:
Yes, but the net the zonal flow must always be zero otherwise all
the air
would gather at one longitude.
That's not strictly true, as you are not taking into account vertical
motion.

I don't think a stratwarm centred on Moscow would bring us snow.
In my earlier reply, I was actually going to add that there are probably
_bad_ places for it to occur - but when I wrote the sentence it looked a
bit patronising, so I deleted it. I agree with what you are saying up to
a point, but as I said before I think you are over simplifying the
dynamics.

Yes, I can find it difficult to express an honest opinion without sounding
abrasive. For instance, isn't it Will who is being simplistic expecting that
every stratwarm will lead to a cold UK? But perhaps he is just being
optimistic :-)

My ideas are simple because I am trying to understand the underlying
mechanism. If stratwarms are the missing piece of the jigsaw, then it
may be possible to construct a simple model of polar winters. I think
that within fifty years we will be able to predict the
movements of the polar vortex and the polar night jet stream, if they still
exist then. (With no polar ice we may have a permanent stratwarm, and no
polar vortex.)

As I see it the stratwarm does not replace the polar vortex, just push it
off the pole. Am I correct? So it depends in which direction that nudge
is - into the eastern or western hemispheres.

I also see the polar night jet determining the polar front. When a stratwarm
occurs the length of the polar night jet increases but its average latitude
remains the same. If a large oscilation brings the polar front south over
the UK then we get cold weather. But the oscilations in the polar night jet
possibly depend on topography and atmospheric tides. So I agree that I did
oversimplify the dynamics but I do believe that they can be determined.

Cheers, Alastair.

"Alastair McDonald" wrote in message
...

"Freddie" wrote in message
.net...
On Wed, 26 Dec 2012 12:22:18 -0000, "Alastair McDonald"
wrote:
Yes, but the net the zonal flow must always be zero otherwise all
the air
would gather at one longitude.
That's not strictly true, as you are not taking into account vertical
motion.

I don't think a stratwarm centred on Moscow would bring us snow.
In my earlier reply, I was actually going to add that there are probably
_bad_ places for it to occur - but when I wrote the sentence it looked a
bit patronising, so I deleted it. I agree with what you are saying up to
a point, but as I said before I think you are over simplifying the
dynamics.

Yes, I can find it difficult to express an honest opinion without sounding
abrasive. For instance, isn't it Will who is being simplistic expecting
that
every stratwarm will lead to a cold UK? But perhaps he is just being
optimistic :-)


I have never said that every stratwarm leads to a cold UK. What I do say is
that it increases the chances.
My reasoning is simple. A stratwarm will decrease the zonal wind above the
jet (like the present one which is very dramatic at 60N now
http://acdb-ext.gsfc.nasa.gov/Data_s...2012_merra.pdf )
..
This decrease or even reversal will extract energy from the jet due to
increased turbulence and thus increase the potential for blocking. Blocking
increases the chances of winter cold in the UK. There is also a feedback as
stratwarms are usually initiated due to breaking Rossby waves at the
tropopause. This present one certainly was as the warming is still not
evident at 10hPa but is now very suignificant at 150 hPa.

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

At 60-90 deg N the forecast reversal of mean zonal wind is clear in ECMWF's 10-day (at days 9 and 10):

http://wekuw.met.fu-berlin.de/~Aktue...&var=u&lng=eng

This is always worth a look as well. I'll get interested when the EPV points polewards:

http://wekuw.met.fu-berlin.de/~Aktue...w/wdiag/ts.php

Stephen.