How common is this?
http://www.metoffice.gov.uk/weather/..._pressure.html
23 November 2011. The High over Greenland.

In article
,
Weatherlawyer writes:
How common is this?
http://www.metoffice.gov.uk/weather/..._pressure.html
23 November 2011. The High over Greenland.

I had a look, but it's now the chart for the 24th. The "high" is still
there, but is now shown as 998mb. I think it's a case of a computer
algorithm getting over-enthusiastic, and labelling a very minor and
local peak as a "high". The main high pressure centre is well to the
west, as shown by the isobars. There's at least one other such
pseudo-high shown on the map, over Germany, and a pseudo-low just to the
west of Greenland.
--
John Hall
"The power of accurate observation is commonly called cynicism
by those who have not got it."
George Bernard Shaw

On Nov 24, 10:30*am, John Hall wrote:
In article
,

*Weatherlawyer writes:
How common is this?
http://www.metoffice.gov.uk/weather/..._pressure.html
23 November 2011. The High over Greenland.

I had a look, but it's now the chart for the 24th. The "high" is still
there, but is now shown as 998mb. I think it's a case of a computer
algorithm getting over-enthusiastic, and labelling a very minor and
local peak as a "high". The main high pressure centre is well to the
west, as shown by the isobars. There's at least one other such
pseudo-high shown on the map, over Germany, and a pseudo-low just to the
west of Greenland.

The median point is the 1016 mb line though much less that 8 either
side of it counts as col or misty stuff going nowhere.

Do you mean those 1025 thingies east of the 1043?

The Lows in the Arctic/North Atlantic are residual from the
earthquakes and Kenneth that spawned or/and increased during this
spell.
They should have congealed by now according the the T+12 and are
heading this way.

Which means another series of quakes starting up somewhere west of
Iceland and heading down to Indonesia via Japan.

The spell ends tomorrow (the lunar perigee was yesterday, I am still
pondering what happened with that.)

Take a look at Bernard Burton's site for the ASSX charts, don't be
misled by Google searching for brothels for you there though.

Perhaps he aught to change the title of that link. OTOH he will get
more hits with a sexy title.

I've posted some of the stuff I found, you know where -seek and ye
shall find.

Highs and lows are only defined relative to surrounding pressure and
are a human construct. There are no absolutes. The notation in this
instance merely marks the point of highest pressure in that locale.
Plus, yes, enthusiastic labelling.

Stephen.

On Nov 24, 1:04*pm, Stephen Davenport wrote:
Highs and lows are only defined relative to surrounding pressure and
are a human construct. There are no absolutes. The notation in this
instance merely marks the point of highest pressure in that locale.
Plus, yes, enthusiastic labelling.

Or maybe they were looking ahead?

A new spell starts tomorrow but look at T+24 anyway.

06:11 means fog with no Greenland High, not sure about the European
one though. The charts does not give the impression its constructors
were certain of themselves. And I've been waiting for a largish shoe
to drop.

Can't think why though. Just a gut feeling.

Ah, there we go, news just in:
6.2 2011/11/24 10:25:35 41.877 142.710 42.3 HOKKAIDO, JAPAN
REGION

Hmmm...

Maybe it has to go down before it turns up?

On Nov 24, 1:04*pm, Stephen Davenport wrote:
Highs and lows are only defined relative to surrounding pressure and
are a human construct. There are no absolutes. The notation in this
instance merely marks the point of highest pressure in that locale.
Plus, yes, enthusiastic labelling.

Stephen.

I would guess though that (at least in the N Hemisphere winter) that
lower central pressure "highs" are more likely further north over
Greenland/Iceland/Norway given the low mean surface pressure in this
region? ( e.g. http://badc.nerc.ac.uk/data/ecmwf-era/pics/mslp.gif )

Richard

On Nov 24, 1:53*pm, Richard Dixon wrote:
On Nov 24, 1:04*pm, Stephen Davenport wrote:

Highs and lows are only defined relative to surrounding pressure and
are a human construct. There are no absolutes. The notation in this
instance merely marks the point of highest pressure in that locale.
Plus, yes, enthusiastic labelling.

Stephen.

I would guess though that (at least in the N Hemisphere winter) that
lower central pressure "highs" are more likely further north over
Greenland/Iceland/Norway given the low mean surface pressure in this
region? ( e.g.http://badc.nerc.ac.uk/data/ecmwf-era/pics/mslp.gif)

Richard

The High is not real anyway because MSL pressures over
the Greenland icecap are meaningless. The place only has "mean sea
level" at the edges and the interior is far too high for any
extrapolation to sea level to be useful. It's probably best to regard
Greenland as a discontinuity in the MSL pattern and to regard the
isobars as formalities which do not necessarily bear any relation to
the circulation at the land surface. The same is true of Antarctica,
even more so because of the greater extent and altitude of the
continent.

Tudor Hughes, Warlingham, Surrey.

Tudor Hughes wrote:
On Nov 24, 1:53 pm, Richard Dixon wrote:
On Nov 24, 1:04 pm, Stephen Davenport wrote:

Highs and lows are only defined relative to surrounding pressure and
are a human construct. There are no absolutes. The notation in this
instance merely marks the point of highest pressure in that locale.
Plus, yes, enthusiastic labelling.

Stephen.

I would guess though that (at least in the N Hemisphere winter) that
lower central pressure "highs" are more likely further north over
Greenland/Iceland/Norway given the low mean surface pressure in this
region? ( e.g.http://badc.nerc.ac.uk/data/ecmwf-era/pics/mslp.gif)

Richard

The High is not real anyway because MSL pressures over
the Greenland icecap are meaningless. The place only has "mean sea
level" at the edges and the interior is far too high for any
extrapolation to sea level to be useful. It's probably best to regard
Greenland as a discontinuity in the MSL pattern and to regard the
isobars as formalities which do not necessarily bear any relation to
the circulation at the land surface. The same is true of Antarctica,
even more so because of the greater extent and altitude of the
continent.

Are isobars over other extensive highland areas such as the
Tibetan plateau regarded in the same fashion?
--
Col

Bolton, Lancashire
160m asl

"Col" wrote in message
...
Tudor Hughes wrote:
On Nov 24, 1:53 pm, Richard Dixon wrote:
On Nov 24, 1:04 pm, Stephen Davenport wrote:

The High is not real anyway because MSL pressures over
the Greenland icecap are meaningless. The place only has "mean sea
level" at the edges and the interior is far too high for any
extrapolation to sea level to be useful. It's probably best to regard
Greenland as a discontinuity in the MSL pattern and to regard the
isobars as formalities which do not necessarily bear any relation to
the circulation at the land surface. The same is true of Antarctica,
even more so because of the greater extent and altitude of the
continent.

Are isobars over other extensive highland areas such as the
Tibetan plateau regarded in the same fashion?
--
Col

Bolton, Lancashire
160m asl
Yes - a bit like thickness charts. There's so much interpolation down to
sea level that they are pretty much worthless.

--
Freddie
Bayston Hill
Shropshire
102m AMSL
http://www.hosiene.co.uk/weather/cumulus/

On Nov 24, 7:02*pm, "Col" wrote:
Tudor Hughes wrote:
On Nov 24, 1:53 pm, Richard Dixon wrote:
On Nov 24, 1:04 pm, Stephen Davenport wrote:

Highs and lows are only defined relative to surrounding pressure and
are a human construct. There are no absolutes. The notation in this
instance merely marks the point of highest pressure in that locale.
Plus, yes, enthusiastic labelling.

Stephen.

I would guess though that (at least in the N Hemisphere winter) that
lower central pressure "highs" are more likely further north over
Greenland/Iceland/Norway given the low mean surface pressure in this
region? ( e.g.http://badc.nerc.ac.uk/data/ecmwf-era/pics/mslp.gif)

Richard

* * * * * * * The High is not real anyway because MSL pressures over
the Greenland icecap are meaningless. *The place only has "mean sea
level" at the edges and the interior is far too high for any
extrapolation to sea level to be useful. *It's probably best to regard
Greenland as a discontinuity in the MSL pattern and to regard the
isobars as formalities which do not necessarily bear any relation to
the circulation at the land surface. *The same is true of Antarctica,
even more so because of the greater extent and altitude of the
continent.

Are isobars over other extensive highland areas such as the
Tibetan plateau regarded in the same fashion?
--
Col

Bolton, Lancashire
160m asl- Hide quoted text -

- Show quoted text -

In South Africa, AFAIK, the standard method is to use the 850 mb
height (in effect the pressure at about 5000 ft) as the surface
isobars. This wouldn't work for Cape Town or Durban, for example and
the MSL isobars are then used, there being a discontinuity on the
charts. This is not as bad as it might seem since the drop from the
tableland to sea level is fairly abrupt.
As Freddie mentions, all this has an effect on 1000-500 thickness
values and an interesting example is seen in comparing Ojmjakon with
Jakutsk in winter. Both are extremely cold (-45 and -50 routinely)
and lie under spectacular inversions of 20 deg and more. Since
Ojmjakon is so much higher than Jakutsk (740 m vs 100 m) the surface
temperature at Ojmjakon is much lower than that in the free air at the
same height over Jakutsk and this low figure is extrapolated to sea
level thus in effect creating a virtual inversion 700 m deep and at
-50°C. There is simply no way of getting a meaningful 1000-500 mb
thickness from Ojmjakon under these conditions. The high altitude of
the surface simply pushes the whole inversion upwards. In summer
(briefly) the opposite applies, Ojmjakon being a high-level heat
source like the Tibetan plateau and many other areas.

Tudor Hughes, Warlingham, Surrey.