This is probably a stupid question but I am having trouble getting my head
round what happens when two big HP's link. For example the MO chart for
Sunday has the large HP west of Ireland and the displaced Siberian High
nearly linking. Both have similar central pressures. Both obviously have a
clockwise flow, sort of going in opposite directions not far from the
merging area. If they did link where would the centre of the new HP be and
why? Meteorologists amongst you probably think this is obvious but I am
interested as there has been conjecture that this might happen and would be
wintry.

Dave. 6.6C, wet and thoroughly horrible, especially after yesterday's great
winter day.

Dave.
Its Len from sunny Basildon, my view is that it would be like two soap
bubbles colliding, each would maintain its own central pressure until an
outer air circulation occured and then the centres would combine and
equalise.
I am sure that I am over simplifying the scenario, but as you say, at the
point of contact there would be an opposing flow. I feel the combining would
be a lot more likely if both areas of high pressure were very flabby with
little if any oppositional flow at that point.

Best regards. Len.


"Dave.C" wrote in message
. ..
This is probably a stupid question but I am having trouble getting my head
round what happens when two big HP's link. For example the MO chart for
Sunday has the large HP west of Ireland and the displaced Siberian High
nearly linking. Both have similar central pressures. Both obviously have a
clockwise flow, sort of going in opposite directions not far from the
merging area. If they did link where would the centre of the new HP be and
why? Meteorologists amongst you probably think this is obvious but I am
interested as there has been conjecture that this might happen and would
be
wintry.

Dave. 6.6C, wet and thoroughly horrible, especially after yesterday's
great
winter day.

Hi Len - didn't realise you were GKN now. Yes, sort of what I thought but
hopefully more answers later.

Sunny Basidon - we wish!

Dave

Yes Dave. I work in Laindon on Southfields and it ain't been very sunny
lately.
"Dave.C" wrote in message
...

Hi Len - didn't realise you were GKN now. Yes, sort of what I thought but
hopefully more answers later.

Sunny Basidon - we wish!

Dave

I'll look out for you then as that's where I walk my dog!
Perhaps my question is not that simple as there have been few answers.
Dave
"GKN" wrote in message
news
Yes Dave. I work in Laindon on Southfields and it ain't been very sunny
lately.
"Dave.C" wrote in message
...

Hi Len - didn't realise you were GKN now. Yes, sort of what I thought
but
hopefully more answers later.

Sunny Basidon - we wish!

Dave

"Dave.C" wrote in message
. ..
This is probably a stupid question but I am having trouble getting my
head
round what happens when two big HP's link. For example the MO chart
for
Sunday has the large HP west of Ireland and the displaced Siberian
High
nearly linking. Both have similar central pressures. Both obviously
have a
clockwise flow, sort of going in opposite directions not far from the
merging area. If they did link where would the centre of the new HP be
and
why? Meteorologists amongst you probably think this is obvious but I
am
interested as there has been conjecture that this might happen and
would be
wintry.

Not sure if I have interpreted your question correctly (which is always
a bad start!) but I think you are expecting these two features somehow
to 'fuse' together - much as two blobs of ink on a bit of paper might
amalgamate if brought together, with a single 'blob' resulting?

We are talking here about two different 'animals' in the meteorological
world, even if the pattern on the surface chart (and therein lies a clue
to the difference) appear the same.

In days gone by, we used to talk much more about 'warm' and 'cold' highs
in strict terms defining the *vertical* distribution of temperature, not
what sort of weather they brought. Bernard Burton discussed this
recently in an answer in the thread entitled "Warm High/Cold High", and
that is worth looking at.

The (warm) high pressure west of Ireland is coupled to the broadscale
circulation, with a strong 'dome' of high contours aloft (where the
cold/dense air is that produces the surface high), and until the
long-wave pattern changes, or is eroded (coupled to changes over North
America and the North Pacific), it isn't going to go very far or change
too markedly in intensity. Latest model output certainly keep it there
or thereabouts until well into February, though there are signs of
retrogression (retreat backwards) at later time-steps.

The high pressure over northern Russia is a more complex affair -
primarily a cold High (central values around 1056mbar/ surface
temperatures -30degC or below), though there is weak ridging aloft as
well - so this is a bit of a hybrid. It will need a major change in the
surface temperature regime / dispersal of snow cover etc., for it to be
thrust aside/weaken - in the sort term, it might do the opposite: see
next paragraph.

In between these two, we have a whole mess of fronts, troughs etc.
(bringing snow to the Med/N Africa), and 'linking' between the two will
depend upon how these behave. Behind cold air intrusions (on the
northerly), pressure will rise, and it will also rise if new snow is
dumped on the existing cover, which then favours extended radiation to
space, further anchoring and allowing extension of the Russian high.
This is the time of year to watch for this, but it needs the Atlantic/NW
European pattern to *remain* meridional (i.e. more north-south movement
than west to east); if a strongly zonal pattern were to be
re-established (as we had earlier in the winter), then maritime/milder
air would drive across the North European/Scandinavia region into
Russia, allowing the aforementioned erosion of the 'cold' high.

The two highs won't 'mix' in the sense that it might be thought - the
pattern could just remain 'as is' for some weeks, though in practice I
think there will be some movement; where the surface outflow from the
highs conflict, then you will find surface fronts (albeit probably of
limited vertical extent and not always shown on classic analysis
charts) - ex Polar Continental (Pc) air-mass from the Russian high and
variants on Polar Maritime/Arctic Maritime (Pm/Am) from the Atlantic
high - or if the latter sinks south, a highly modified Tropical Maritime
(Tm) perhaps.

Isn't meteorology wonderful ;-)

HTH

Martin.

--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

Thank you for taking the time for such a comprehensive answer Martin and
answering the question I was trying to ask! I can more or less understand it
and I think it will help several other people grasp a wider synoptic view of
the current situation. I didn't expect them to merge simply but wasn't
really sure what would happen when people talk about the two HP's "linking".

Dave

"Dave.C" wrote in message
k...
snipbut wasn't
really sure what would happen when people talk about the two HP's
"linking".


.... what I should have said (but it was already an overlong post), was
that two *similar* high cells could indeed appear to link up - this
often can be seen over the Atlantic for example when the forcing is
(initially) weak and a couple of discrete warm high cells are replaced
by a single slightly stronger cell as the upper air drives subsidence
over a wider area and the surface high intensifies - often though even
here you can find that one of the cells is the dominant one.

It is tempting to regard surface pressure features as 'ring-fenced'
because they are defined by isobaric patterns; it is more useful to try
and picture any atmospheric phenomenon as multi-dimensional; advances in
forecasting didn't really come about until a good grasp of upper air
structure was gained by the early balloon flights latter 19th/very early
20th century.

One of the best displays of model output BTW that allows you to display
surface and upper-air features in a strip side-by-side is at:-

http://www2.wetter3.de/

where you can select the run you require then display 3 'strips' of
various fields together.

Martin.