Will Hand wrote:
snip-lots
I said in another thread that I thought that the 564 DAM line was
just a bit further north than it should be. snip
but the persistent closeness of that warm and moist 564 DAM air
is bothering me

"Keith(Southend)" wrote ...


Admittedly, I can't say where the 564 DAM line normally is this time
of year, but looking at the charts I don't see it being particularly
far north.
http://www.wzkarten.de/pics/brack0a.gif
http://www.wzkarten.de/pics/brack1a.gif
http://www.wzkarten.de/pics/brack3.gif
and in the middle of the Atlantic it seem quite far south. Certainly
it's close to us on the near Continent, but am I missing something
here?

.... I've posted the mean 500-1000 hPa thickness (ex. NOAA/ESRL) he-

http://freespace.virgin.net/martin.r...HK_JULmean.gif

I've also looked at the last 8 days of analysis using the wetter3.de
archive. You can see from the mean chart for July that there is a
thermal trough with an axis roughly along 20degW at latitude ~
40/45degN, which I assume is the area that we are talking about?

For the last 8 days, the mean value of thickness at a point 41N, 20W
(where the mean for 1968-1996 is given as 564 dam), was 565dam: +1dam
over the long-term mean. This doesn't seem to me to show anything
excessively warm. Of the last 8 days, 5 had 00Z values at or below
564dam, with a temporary peak (passing wave) of 573 dam.

I also looked at a couple of other warm Julys (warm in BI that is:
July 1995 is one example), and the mean 564 dam contour was
comfortably further north than this mean - typically lying from Nova
Scotia to Greater Paris, with a dip in the 15-25degW area. Given that
these are *mean* values, the day-to-day position must have been even
further north than that for extended periods.

I can't see from any data that I have available that there is anything
particularly unusual about the latitudinal position of the 564dam
contour.

Martin.


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

Alastair wrote:

Graham,

What you are saying makes more sense to me. The cold pool of surface
water in the North Atlantic seems to be flowing out from Baffin Bay.
My idea is that it is melting Arctic sea ice and/or melting ice bergs
from a fast retreating Greenland ice sheet. Melting ice would explain
why the cold water remains on the surface rather than sinking. It is
fresh water and so does not the higher density of saline sea water.
OTOH why don't we see it coming down from the east of Greenland.

I don't think it has had anything to do with melting ice. I don't altogether
trust the anomalies I'm using but it seems to have mostly developed in situ.
In any case, a large part of the cold anomaly would appear to be over, and
even to the south of the NAD. I suspect a cold Canadian winter/spring is a
more likely candidate with colder than normal winds from that region cooling
the surface waters.

I had a similar disagreement nearly forty years ago when a record number of
icebergs were sighted over the Grand Banks in the spring and summer. The
melting of these was widely announced by other Met Office experts as being
responsible for a huge mid-Atlantic cold pool and hence the UK's cold
summer. This theory was widely published in the media. I had many doubts
about this theory and, first of all, calculated how much cooling the melting
of all the ice-bergs would have caused, making as many allowances as
possible to get the largest figure I could. The result was that the cooling
could have been no more than a tenth of what was observed, even assuming all
the ice had melted and that there had been no turbulent mixing to disperse
the melt-water. What also should have scuppered their theory, if they'd
taken the time to look at the data, was that the bulk of the cold pool was
formed before any melting occurred. Like most urban myths, their explanation
persisted.



I suspect that the features we see in Western Europe at present and
blame on global warming are caused by the melting Arctic sea ice. When
that is completely melted, there will be a new regime much like that
dreamed of by Will.

Again, I'm not too sure what's the result of melting ice and/or GW. The
problem I see is that most of the extra melting occurs within the Arctic and
the melt-water mostly stays there during the summer and I doubt that it adds
anything to cooling the Atlantic. The only thing I am sure of is that Winter
northerlies are much less cold than they used to be because of the small
area of ice off E Greenland in winter.

The other thing I'm pretty sure of is that we'll soon see another record low
amount of ice in the Arctic, probably by 2011. I also think that that will
be followed by another massive drop in ice-cover by 2015, quite probably
with open water from the Russian coastline to the North Pole.

--
Graham P Davis, Bracknell, Berks., UK. E-mail: newsman not newsboy
"I wear the cheese. It does not wear me."

Graham wrote:


Looks like the only thing that can save our sorry bunch!!

Hard to believe the Aussies have lost 5 or 6 world class players and
yet they can still outclass England in their own back yard.
Hope we don't lose 5-0 that would be a grim Summer!
Let's hope we get some heavy showers in Cardifff soon as the sorry bunch
who call themselves the England cricket team are struggling on a flat
pitch at 55 for 4

252-9 at close of play. Anderson and Monty not out 21 and 7. Phew!

--
Graham P Davis, Bracknell, Berks., UK. E-mail: newsman not newsboy
"I wear the cheese. It does not wear me."

On Jul 12, 5:47*pm, Graham P Davis wrote:
Graham wrote:

Looks like the only thing that can save our sorry bunch!!

Hard to believe the Aussies have lost 5 or 6 world class players and
yet they can still outclass England in their own back yard.
Hope we don't lose 5-0 that would be a grim Summer!
Let's hope we get some heavy showers in Cardifff soon as the sorry bunch
who call themselves the England cricket team are struggling on a flat
pitch at 55 for 4

252-9 at close of play. Anderson and Monty not out 21 and 7. Phew!

--
Graham P Davis, Bracknell, Berks., UK. *E-mail: newsman not newsboy
"I wear the cheese. It does not wear me."

Well done Monty! Straight out of Kipling "Bumpy pitch and the last man
in."

Cheers, Alastair.

"Martin Rowley" wrote in message
...
Will Hand wrote:
snip-lots
I said in another thread that I thought that the 564 DAM line was just
a bit further north than it should be. snip
but the persistent closeness of that warm and moist 564 DAM air is
bothering me

"Keith(Southend)" wrote ...


Admittedly, I can't say where the 564 DAM line normally is this time of
year, but looking at the charts I don't see it being particularly far
north.
http://www.wzkarten.de/pics/brack0a.gif
http://www.wzkarten.de/pics/brack1a.gif
http://www.wzkarten.de/pics/brack3.gif
and in the middle of the Atlantic it seem quite far south. Certainly it's
close to us on the near Continent, but am I missing something here?

... I've posted the mean 500-1000 hPa thickness (ex. NOAA/ESRL) he-

http://freespace.virgin.net/martin.r...HK_JULmean.gif

I've also looked at the last 8 days of analysis using the wetter3.de
archive. You can see from the mean chart for July that there is a thermal
trough with an axis roughly along 20degW at latitude ~ 40/45degN, which I
assume is the area that we are talking about?

For the last 8 days, the mean value of thickness at a point 41N, 20W
(where the mean for 1968-1996 is given as 564 dam), was 565dam: +1dam over
the long-term mean. This doesn't seem to me to show anything excessively
warm. Of the last 8 days, 5 had 00Z values at or below 564dam, with a
temporary peak (passing wave) of 573 dam.

I also looked at a couple of other warm Julys (warm in BI that is: July
1995 is one example), and the mean 564 dam contour was comfortably further
north than this mean - typically lying from Nova Scotia to Greater Paris,
with a dip in the 15-25degW area. Given that these are *mean* values, the
day-to-day position must have been even further north than that for
extended periods.

I can't see from any data that I have available that there is anything
particularly unusual about the latitudinal position of the 564dam contour.

Martin.


Thanks ever so much for that Martin. It is sort of re-assuring I guess,
although 1 DAM over the long term mean may not sound a lot it takes on a
significance if we are looking for signs of warming. Take your point about
1995 et al though. I suppose if we see the mean over southern England
creeping up then that would be more definite evidence as historical mean
thickness values over the ocean will be calculated on limited sonde data
with satellite retrievals in their infancy and subject to large errors due
cloud contamination etc.

Will
--

On Sat, 11 Jul 2009 at 21:44:45, Graham wrote
in uk.sci.weather :

The important thing is that it should rain at Cardiff for most of
tomorrow.

Looks like the only thing that can save our sorry bunch!!

Hard to believe the Aussies have lost 5 or 6 world class players and
yet they can still outclass England in their own back yard.
Hope we don't lose 5-0 that would be a grim Summer!

Well, at least we can't quite do *that*, now...
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

On Sun, 12 Jul 2009 at 08:35:11, Alastair
wrote in uk.sci.weather :

In case there is anyone else, like me

And me...

, who does not understand the
significance of the 564 DAM, I found the following on the Met Office
web site:

Thickness lines
Pressure decreases with altitude, and thickness measures the
difference in height between two standard pressure levels in the
atmosphere. It is proportional to the mean temperature of this layer
of air, so is a useful way of describing the temperature of an
airmass.

Weather charts commonly show contour lines of 1,000-500 hPa thickness,
which represent the depth (in decametres, where 1 dam = 10 m) of the
layer between the 1,000 hPa and 500 hPa pressure levels. Cold, polar
air has low thickness, and values of 528 dam or less frequently bring
snow to the UK. Conversely, warm, tropical air has high thickness, and
values in excess of 564 dam across the UK often indicate a heatwave.
http://www.metoffice.gov.uk/weather/uk/guide/key.html

Thanks, that was very useful.

What happens when 1,000 hPa (or lower) is the sea-level pressure,
though?
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

On Sun, 12 Jul 2009 at 18:47:43, Graham P Davis
wrote in uk.sci.weather :

Graham wrote:


Looks like the only thing that can save our sorry bunch!!

Hard to believe the Aussies have lost 5 or 6 world class players and
yet they can still outclass England in their own back yard.
Hope we don't lose 5-0 that would be a grim Summer!
Let's hope we get some heavy showers in Cardifff soon as the sorry bunch
who call themselves the England cricket team are struggling on a flat
pitch at 55 for 4

252-9 at close of play. Anderson and Monty not out 21 and 7. Phew!

Perhaps they should promote Anderson to opener - after all, he never
gets out for a duck...
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

On Sun, 12 Jul 2009 at 11:55:23, Alastair
wrote in uk.sci.weather :

On Jul 12, 5:47*pm, Graham P Davis wrote:
Graham wrote:

Looks like the only thing that can save our sorry bunch!!

Hard to believe the Aussies have lost 5 or 6 world class players and
yet they can still outclass England in their own back yard.
Hope we don't lose 5-0 that would be a grim Summer!
Let's hope we get some heavy showers in Cardifff soon as the sorry bunch
who call themselves the England cricket team are struggling on a flat
pitch at 55 for 4

252-9 at close of play. Anderson and Monty not out 21 and 7. Phew!

--
Graham P Davis, Bracknell, Berks., UK. *E-mail: newsman not newsboy
"I wear the cheese. It does not wear me."

Well done Monty! Straight out of Kipling "Bumpy pitch and the last man
in."

I was thinking that, myself!
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)