Can anyone tell me why the UK weather has been set in an anticyclonic
pattern, virtually non-stop, since the beginning of 2003?

And Can anyone say when things are going to change?

The resulting fine sunshine and dry weather (but not the heat) has
been good for going out and sense of well-being. However, I am
concerned that there could be drought problems, come 2004, if this
anticyclonic weather pattern persists through the autumn and winter.

In SE England, 70% of the water supply comes from groundwater in
aquifers. Regular, moderate rainfall over the autumn and winter is
vital to recharge these. From the Environment Agency's water resources
summary for August, I see that soil moisture deficits are in excess of
100 mm over much of England; and the flow rates of some rivers, in
England and Wales, is less than half the average for August.

Can anyone tell me why the UK weather has been set in an anticyclonic
pattern, virtually non-stop, since the beginning of 2003?

Having replied to your first respondant, I ought to reply to your question!
Airflow does sometimes get into a long term rut, and there is an element of it
just balancing out the cyclonic period 2000 to 2002 (I agree with you that this
is not a reason for complacency). However, this summer was not especially
anticyclonic - though the last few weeks obviously have been. After a long dry
spell, the dryness of the ground forces a positive feedback on the climate
system, discouraging rain, amplifying the original 'dry' signal. This is
probably how the dry spell seems to gain momentum. I'll leave it to others to
suggest when it will change, though I see from the radar it already has done
further north today!

Julian Mayes, West Molesey, Surrey.

"JJCMayes1" wrote in message
...
Can anyone tell me why the UK weather has been set in an anticyclonic
pattern, virtually non-stop, since the beginning of 2003?

Having replied to your first respondant, I ought to reply to your question!
Airflow does sometimes get into a long term rut, and there is an element of it
just balancing out the cyclonic period 2000 to 2002 (I agree with you that
this
is not a reason for complacency). However, this summer was not especially
anticyclonic - though the last few weeks obviously have been. After a long dry
spell, the dryness of the ground forces a positive feedback on the climate
system, discouraging rain, amplifying the original 'dry' signal. This is
probably how the dry spell seems to gain momentum. I'll leave it to others to
suggest when it will change, though I see from the radar it already has done
further north today!

But presumably the SST's are well above average for the time of year
due to the warm summer, won't this encourage deeper depressions
this autumn and lead to wetter conditions?

Not that there has been much sign of *that* happening yet........

Col
--
Bolton, Lancashire.
160m asl.
http://www.reddwarfer.btinternet.co.uk

But presumably the SST's are well above average for the time of year
due to the warm summer, won't this encourage deeper depressions
this autumn and lead to wetter conditions?

Col,

quite possibly, though the upper trough / ridge patterns will determine where
the depressions actually go (e.g. autumn 1976 switched to a southerly track to
counter the dry summer - it was already very wet by this date in 1976). The
other factor favouring in a similar vein is that high SSTs may boost shower
intensity (i.e. more unstable polar maritime airstreams) and possibly frontal
pptn. too - with the return of moist westerlies at some time this autumn,
Bolton should eventually be in the firing line!

yours,

Julian Mayes, West Molesey.

"Joan Lee" wrote in message
Can anyone tell me why the UK weather has been set in an anticyclonic
pattern, virtually non-stop, since the beginning of 2003?

Joan,

I'd love to know the same answer, surely with *all* the scientific
background and knowledge in the NG there must be someone who has had
pointers over the past 12 months which have been unusual?

C'mon Will.... dazzle us :-)

A

"Col" wrote in message
...

"JJCMayes1" wrote in message
...
Can anyone tell me why the UK weather has been set in an anticyclonic
pattern, virtually non-stop, since the beginning of 2003?

Having replied to your first respondant, I ought to reply to your
question!
Airflow does sometimes get into a long term rut, and there is an element
of it
just balancing out the cyclonic period 2000 to 2002 (I agree with you
that
this
is not a reason for complacency). However, this summer was not
especially
anticyclonic - though the last few weeks obviously have been. After a
long dry
spell, the dryness of the ground forces a positive feedback on the
climate
system, discouraging rain, amplifying the original 'dry' signal. This is
probably how the dry spell seems to gain momentum. I'll leave it to
others to
suggest when it will change, though I see from the radar it already has
done
further north today!

But presumably the SST's are well above average for the time of year
due to the warm summer, won't this encourage deeper depressions
this autumn and lead to wetter conditions?

Long hot summers are just as often followed by long warm autumns as they
are by wet ones. 1921, 1947, 1959 and 1990 are probably the best
examples. As Julian says, it depends on the favoured autumnal depression
track, which in turn depends on the positioning of the jet-stream.

And I can also confirm Julian's point about 2003 not being all /that/
anticyclonic. Here are the differences from normal of monthly sea-level
pressure for London and Stornoway in mbar:

London Stornoway
January +0.5 +2.0
February +3.5 +0.5
March +6.5 +4.5
April +2.0 +2.0
May +1.0 -4.5
June -2.0 -4.5
July -3.0 -4.0
August +2.0 +4.5
Septempber so far
+5.0 +6.0

It has, though, been remarkably dry since early January in many
eastern districts. Shoeburyness in Essex has had only 244mm since
1 Jan -- a shortfall of about 35%. The deficit has been as great
in eastern Scotland as it has been in southeast England.

Philip Eden