2006-7- part 3: The four-day winter - Feb 8-11!
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What is happening to our winters??
I'm old enough to remember cold snowy ones - I was born
just before the 1962-63 winter - although obviously I
don't remember that - and enjoyed weeks of freezing
temperatures and snow in the winters of (in particular)
the late 70s and mid 80s. Such conditions were
"normal" enough that being sent home from
school was a rarity - although I do recall one occasion
when school didn't open because the snowdrifts were
preventing the doors being opened! Nowadays, if I want to
see snowdrifts like that it's necessary to get up into
the mountains, it seems. And in addition, 2cm of snowfall
brings everything grinding to a halt!
The last few winters have seen typically brief cold snaps
with mild conditions dominating the rest of the time and
2006-7 has (so far) been no different. The synoptic
pattern has remained mobile and zonal with the UK
receiving air from well out to the SW most of the time.
This is the main factor - climate change simply meaning
that the temperatures have been a little higher than they
would otherwise be. The synoptic pattern is what is
crucial to giving the UK cold snowy conditions, as indeed
it managed to on Feb 8-11.
Late January saw high pressure established over the UK
and temperatures slowly fell due to overnight radiative
cooling in the rather stagnant airmass. Then, in the
first week of February, a ridge of high pressure over
Greenland intensified: with low pressure over Scandanavia
a cold northerly engulfed the UK bringing both daytime
and nightime temperatures further down. However, by
February 6th, the Greenland ridge had diminished somewhat
allowing a developing Atlantic low to start heading for
us. By the 8th, low pressure was centered just SW of
Ireland, whilst the remnants of the cold air sat over the
Such a set-up is known as a "battleground", the
battle being between the resident cold air and the milder
moisture-laden Atlantic air trying to get in. Where these
meet, snow is commonly the result, and potentially an
awful lot of it!
The snow arrived in Machynlleth in the morning of
Thursday February 8th. It fell steadily all day,
sometimes light, sometimes heavy, so that even at
valley level around 10cm accumulated. This is the
view from Penyrallt on that afternoon.
Thursday's snow was well-forecast but in terms of
normally being able to predict the weather 24
hours in advance with some accuracy, Friday's
took everyone by surprise from professional
meteorologists to amateurs like me. Complex
developments in the Biscay area led to another
series of fronts pushing up early on Friday
morning so that new severe weather warnings were
out by the morning and once again the snow fell
all day, replacing the partially thawed fall of
the previous day.
I betted myself that no such thaw had occurred in
the hills, though, and on Saturday 10th three of
us set off up the Dylife mountain road, for a
The road was fine at 300m ASL...
...but around the 400m contour we found where the
snowplough had given up! The cars belonged to
sledgers in a nearby field. Having no sledge
ourselves, or indeed the huskies to pull one
along, we set off on foot....
...which proved exceedingly hard-going. The road,
sunken between higher banks, was badly
drifted-up, depths varying from ankle to
thigh-depth. To make matters more complicated,
advection-fog was forming at the snow-air
interface due to the milder sou'westerly now
blowing - its moisture was condensing at surface
where the snowfields were cooling it, just as
sea-fogs form in early summer when hot humid air
is advected over a cooler sea. The end result was
that the fog was thickest at this level, to the
extent that it was impossible to tell where the
snow was deepening or shallowing, making for very
tough uphill progress! Here, we abandoned our
In a rare slight clearance I managed to catch one
drift in more detail....
...before we ploughed our way back down and set
off back to the valley. This was taken on the way
back, looking up into the foggy snowfields.
Sunday saw overnight heavy rain clearing to a
beautiful day, so alone this time I decided to
give the pass another go. A substantial thaw was
now underway and the road was passable to 4x4s
with decent ground-clearance....
Inland, the scene was very wintry. Central and
Southern Wales bore the brunt of this event...
Some major drifts over a metre in depth still
remained, pock-marked where they had been melted
from the surface downwards and with the sound of
meltwater gurgling beneath them...
This one must have been huge originally! Now just
1.5m in depth.
I liked this pattern of furrows made into the
remaining drifts on a nearby hillside, presumably
by heavy rainfall running-off.
So that, then, appears to have been that for
winter 2006-2007. Disappointing for cold
weather-fans, but when the snows did come,
everyone made the most of them! I'm sure we'll
see cold winters again, but for now my
firewood-stash seems to grow year-on-year to an
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