Have a look at
http://www.climate-uk.com/temp.htm
There is a marked periodicity in the top (10-day mean)
chart, especially in the westerly index. In previous years
periodicities have come and gone pretty quickly, and I can't
remember seeing one quite as marked as this. It's not a
statistical artifact ... it's easy to remember the westerly
spells in early Jan, early Feb, mid-Mar, early to mid
April, and late May, and also the blocked spells
between.

Philip Eden

"Philip Eden" philipATweatherHYPHENukDOTcom wrote in message



http://www.climate-uk.com/temp.htm

There is a marked periodicity in the top (10-day mean) chart, especially
in the westerly index. In previous years periodicities have come and gone
pretty quickly, and I can't remember seeing one quite as marked as this.

It's not a statistical artifact ... it's easy to remember the westerly
spells in early Jan, early Feb, mid-Mar, early to mid April and late May,
and also the blocked spells between.


I'm sure that I would find this interesting if I could only follow it.

Where do you get your backgrounds from?


--
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"Philip Eden" philipATweatherHYPHENukDOTcom wrote in message
...
Have a look at
http://www.climate-uk.com/temp.htm
There is a marked periodicity in the top (10-day mean)
chart, especially in the westerly index. In previous years
periodicities have come and gone pretty quickly, and I can't
remember seeing one quite as marked as this. It's not a
statistical artifact ... it's easy to remember the westerly
spells in early Jan, early Feb, mid-Mar, early to mid
April, and late May, and also the blocked spells
between.

Philip Eden

A 30-35 day oscillation has been reported in the literature in association
with N Atlantic sector blocking and retrogression of the jet,this may be a
harmonic of a 70 day signal.
Causes may be an internal oscillation involving barotropic interaction with
topography,probably unlikely in the Atlantic,or interaction of synoptic
transients with the mean flow.I'll find some references if you're
interested,

--
regards,
David

add '17' to Waghorne to reply

"Waghorn" wrote in message


A 30-35 day oscillation has been reported in the literature in association
with N Atlantic sector blocking and retrogression of the jet,this may be a
harmonic of a 70 day signal.

There is an history of inexplicable cycles in weatherlore too. It is
difficult to relate it to anything as regular as these things though.

This sort of thing. Somewhat unscientifically set out, as a mere
collection belying a total lack of research:

In Janiveer if the sun appear, March and April pay full dear.

January warm, the Lord have mercy!

[Because a premature growth of vegetation is liable to suffer severe
damage from spring frosts -Editor]

(I had thought the editor's comments unlikely. I'd thought it more
likely to be a reference to the prevalence of T.B. and influenza.)

While frost might damage the cross fertilisation process of some fruit
trees it isn’t likely to do worse to any vegetation. I remember once a
hard frost took all the leaves off the conker trees where I used to
live. They soon grew back.)

A summerish January; a winterish spring.

If January calends be summery gay, it will be wintry weather until the
calends of May.

(Well that one was true enough.)

A January spring is worth nothing –Scotland.

A warm January, a cold May.

Not really illuminating but totally inexplicable (if true.)



--
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"Waghorn" wrote in message
news:d8cv29
A 30-35 day oscillation has been reported in the literature in
association with N Atlantic sector blocking and retrogression of the
jet,this may be a harmonic of a 70 day signal.
Causes may be an internal oscillation involving barotropic interaction
with topography,probably unlikely in the Atlantic,

.... the short-range (synoptic / day-to-day scale) effect of the
Greenland land/ice mass on N. Atlantic disturbances is accepted (i.e.
the Kap Farvel / Cape Farewell distortion), and I believe that in recent
years, the whole subject of the interaction with the Northern
Hemispheric broadscale flow has been investigated and found to be a
fertile subject. Your mention of topography had 'little bells' ringing
at the back of my mind of a study that was published several years ago
that directly linked the presence of Greenland with distortions in the
long-wave pattern, but after a search, I can't come up with that
particular entry. However, I did come up with :-

http://folk.uio.no/jegill/papers/pet...004_tellus.pdf

"Numerical simulations of Greenland's impact on the Northern Hemisphere
winter circulation" from which the following is extracted (from the
Conclusion):-
quote The present study shows that Greenland has a significant impact
on the general circulation of the Northern Hemispheric extratropics, at
both lower and mid-tropospheric levels. Due to the presence of
Greenland, the storm tracks are shifted southward over the North
Atlantic and thus the mountain contributes to less precipitation at the
western coast of Norway and over the North Atlantic. Greenland has a
damming effect on the air mass on its west side, which is cooled down by
radiative heat loss during the polar winter, leading to less
geopotential thickness in the area and thus less 500-hPa geopotential
height than in the simulation without Greenland. The cold air also
causes increased baroclinicity over North America leading to an increase
in cyclone activity. On the east side of Greenland, the mountain causes
higher sea level pressure which is associated with increased
geopotential height at the 500-hPa level. The study demonstrates that
Greenland’s impact on the general circulation is fundamentally different
from the impact of the Rocky Mountains and the Tibetan Plateau. Unlike
the case of the classic Rossby wave where westerlies impinge on a major
mountain range and a trough is created downstream of the mountain,
Greenland’s impact seems mainly to be a perturbation of the flow on the
upstream side of the mountain generated by damming of cold low-level air
masses. /quote

If I understand aright, then we are not looking at the classic
'Rossby-wave' type of distortion of the pattern, but an indirect control
on same due to changes in the temperature regimes either side of
Greenland.

Whilst searching, I also came upon a few links relating climatological
regime changes over Greenland (from Ice core evidence) and the Asian
monsoon - this implies quite complex and fundamental teleconnections
north-to-south as well as west-to-east: who'd be a climate scientist!



Martin.

Most of the weather lore was based around the people at the time liking
things to follow in 'proper' order, hence a warm January was deemed as
foreboding and not how 'it should be' and therefore something sinister was
at work, which usually meant that a cold spring would follow as a form of
recompense for the disorder.

This goes against findings by Lamb who found that in around 70% of the
instances, a warm winter is followed by a warm spring and so on until the
cycle gets 'broken'.
________________________
Nick G
Exe Valley, Devon
50 m amsl

"Michael Mcneil" wrote in message
news:dc545d140c4aaae1feddb6b12a0b994e.45219@mygate .mailgate.org...
"Waghorn" wrote in message


A 30-35 day oscillation has been reported in the literature in
association
with N Atlantic sector blocking and retrogression of the jet,this may be
a
harmonic of a 70 day signal.

There is an history of inexplicable cycles in weatherlore too. It is
difficult to relate it to anything as regular as these things though.

This sort of thing. Somewhat unscientifically set out, as a mere
collection belying a total lack of research:

In Janiveer if the sun appear, March and April pay full dear.

January warm, the Lord have mercy!

[Because a premature growth of vegetation is liable to suffer severe
damage from spring frosts -Editor]

(I had thought the editor's comments unlikely. I'd thought it more
likely to be a reference to the prevalence of T.B. and influenza.)

While frost might damage the cross fertilisation process of some fruit
trees it isn't likely to do worse to any vegetation. I remember once a
hard frost took all the leaves off the conker trees where I used to
live. They soon grew back.)

A summerish January; a winterish spring.

If January calends be summery gay, it will be wintry weather until the
calends of May.

(Well that one was true enough.)

A January spring is worth nothing -Scotland.

A warm January, a cold May.

Not really illuminating but totally inexplicable (if true.)



--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

"Martin Rowley" "Waghorn" A 30-35 day oscillation has been reported in
the literature in
association with N Atlantic sector blocking and retrogression of the
jet,this may be a harmonic of a 70 day signal.
Causes may be an internal oscillation involving barotropic interaction
with topography,probably unlikely in the Atlantic,

................................. Your mention of topography had 'little
bells' ringing at the back of my mind of a study that was published
several years ago that directly linked the presence of Greenland with
distortions in the long-wave pattern, but after a search, I can't come up
with that particular entry.
.................................................. ............................................
Whilst searching, I also came upon a few links relating climatological
regime changes over Greenland (from Ice core evidence) and the Asian
monsoon - this implies quite complex and fundamental teleconnections
north-to-south as well as west-to-east: who'd be a climate scientist!



Martin.
Yes,I was precising old notes,but at the time I thought-'Wot about
Greenland?'.
I will look up the original reference and post further if it's illuminating.
There is a note about a possible relation to the Madden Julien Oscillation
as well,

--
regards,
David

add '17' to Waghorne to reply

"Waghorn" I will look up the original reference and post further if it's
illuminating.
There is a note about a possible relation to the Madden Julien Oscillation
as well,

The reference is-
Plaut&Vautard,Spells of Low Frequency Oscillations and Weather Regimes in
the Northern Hemisphere,J Atmospheric Sciences,V53,no2,1994,p210-
(not available online unless you purchase from the AMS website)
They use Singular Spectrum Analysis of 700Hpa GPH fields .Can't comment on
the technique ,.but the paper seems well regarded and cited.
Apparently interaction with topography may play a role but is not a
sufficient explanation,synoptic eddy forcing is the major player.Particular
phasing of the 30-35 day oscillation is found to precede major
European-Atlantic blocking,as occurs in the striking pattern pointed out by
Philip.This has interesting results for predictability of such blocks.
Whether extratropical oscillations precede or lag tropical oscillations was
questioned in the nineties.I believe the view now is that at least some
precede-the mechanism is the movement of PV anomalies with the Rossby waves
equatorward triggering tropical convection.There are of course feedbacks,and
tropical heating anomalies are known to effect the downstream long wave
pattern.
Anyway,as you point out ,there are a multitude of weak teleconnection
patterns,

--
regards,
David

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