.....as in this pic with a well-defined snowline
on the flanks of Moel Fadian, as seen from the
Machynlleth-Llanidloes mountain road. A virtual
whiteout exists above - that is: when fresh snow
covers the ground, the cloudbase is low and it is
snowing heavily. Under such circumstances, the
ground can seem to merge imperceptibly with the
air, creating highly dangerous conditions for
mountain walkers trying to navigate their way off
the hill...
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...and in this one, taken on the same day -
January 14th. The sleety snow is badly obscuring
the view now and can be seen falling in the
foreground. If the air close to the ground is not
cold enough, falling snowflakes will begin to
melt as they near ground level, and the result is
of course sleet - horrible wet globby stuff that
always seems to find its way down your collar
before it has completely melted! But onto
something more significant:
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The cold snap at the end of January 2004 gave way
to very mild (even warm) south-southwesterly
winds with a long, long "fetch" down
into tropical areas (see sketch above). Laden
with moisture, they set in at the beginning of
February and lasted for several days. Low after
low formed in this airstream and ran into the UK
from the SW. In these conditions rain tends to
fall on western hills with dryer areas to the
east ("rain-shadows").
Gales or local storm-force winds were one feature
of this setup but the rain was the main one. It
began raining on Saturday February 1 and didn't
really stop until late in the night of Wednesday
February 4th, by which time Capel Curig in
Snowdonia had recorded over ONE FOOT of rainfall!
261mm of this were recorded on the 3rd and 4th!!
The following images track the worst 48 hours
from 8pm on the 2nd to 8pm on the 4th, during
which heavy rain fell almost relentlessly:
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After a night
of steady rain, Tuesday morning showed no letup,
as in this pic taken in lashing, pelting rain
from squelchy fields on Wylfa, looking NE towards
Machynlleth with the Dyfi already well out across
the fields...
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By the afternoon, with the rains continuing, the
water was getting deeper...
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...and
it was no surprise to see 5-6 inches of water on
the A487 out to Dyfi Bridge - still passable with
care but with high tide due at 8pm the situation
would now deteriorate as the incoming tide in the
estuary only 10km downstream would start to pond
the floodwaters....
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By the
following morning (Wednesday 4th) despite a brief
pause in the rain overnight, deep water filled
the valley from side to side - and down it came
again! It was a case of go out, take pix, come
home & dry out the camera (and find dry
clothes!).
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At the
Railway Bridge in Machynlleth there is a bit of a
dip in the road that has caught a lot of people
out over the years. Just passable at high tide on
Wednesday morning in transit-type vans and bigger
vehicles, but rising again...
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By Wednesday afternoon after several more hours
of downpour the water simply ran off the
hillsides and across the fields wherever it
could. This is Machynlleth golf-course...
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...and this
is the "brook" that passes under the
Newtown road at Abergwyddel. All heading for one
place only - the main Dyfi valley....
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By 4pm on
Wednesday following the A487 out to Dyfi Bridge
was no longer an option. The water in the centre
of the road is over a foot deep with a powerful
standing wave on top of that caused by the force
of the water pouring through the steel railings
on the R. The LHS of the road is raised as there
is a separate cycle-track along there.
This isn't the river itself. That is another 500m
away - the houses in the background are by the
bridge!
It's not the depth of the water that is the main
issue but the strength of the current. A year or
so back a cyclist attempted, in similar
conditions, to wade this section before the steel
railings were put in. He was swept into an old
fence and his life was only saved by a major
human effort...
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24 hours later at the same spot...
The rain stopped on Wednesday night, thankfully.
The floods dropped back over the next day
(although the railway bridge was still impassable
to cars), revealing damage to the tarmac
road-surface and lots of debris caught up in
fences and hedges... |
....and in other areas signs of landslipping.
This is in the valley of the Afon Wen near
Dolgellau, where an old landslip had reactivated
bringing further trees and debris down into the
river.
261mm of rain in 48 hours only 40 miles to the N
of here; near-record warm temperatures (records
were indeed broken in some areas that week) -
that's what can happen when the air comes up from
the tropics in wintertime.
It is perhaps fortunate that such prolonged
severe rain events are comparatively unusual in
the UK! A flood like this maybe happens one
winter in three although less powerful ones are
witnessed most winters. |
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