Pont-Faen
Flash Flood, 5th September 2008 discussion
There
was a flash flooding event around the Battle Hill area of
Powys (SO 0133).
This is
a sparsely populated area however dozens of homes were flooded
by runoff flowing down the hills through properties (not on
a flood plain). 4" of rain was reported in around an
hour between 1:30 - 2:30pm.
Several
foot bridges have been destroyed, with an old road bridge
at pont-faen being seriously damaged.
Please
see this
thread for further information
Today's
analysis by Retron - Friday
17th October
2008
Here
is a summary of the NWP output for noon (GMT) on Tuesday.
Issued 0501z, 17th October 2008
Analysis
and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
Westerlies cover the UK, with a weak ridge atop the British
Isles. WSW'lies affect the UK tomorrow as a weak trough moves
eastwards, followed by SSW'lies on Sunday. Monday sees strong
southerlies, with a trough to the west.
T+120
synopsis
http://85.214.49.20/pics/Rtavn12014.png
/ http://85.214.49.20/pics/Rtavn1201.png
http://85.214.49.20/pics/Rukm1201.gif
http://85.214.49.20/pics/Recm1201.gif
/ http://www.meteociel.fr/modeles/nogapse_cartes.php
The jetstream chart shows a trough over the UK, with a broad
westerly flow over the Atlantic. At the 500hPa level there's
also a trough, with WNW'lies aloft. MetO shows an upper trough
too, while ECM has an upper trough slightly further west.
GEM also has an upper trough to the immediate west of the
UK.
At the surface, GFS brings WSW'lies, with a ridge to the SW.
MetO shows a weak ridge with NW'lies for England and Wales
and westerlies elswhere, while ECM has a trough over eastern
England with WNW'lies elsewhere. Much the same is true with
GEM, which has stronger westerlies for all.
Evolution
to T+168
Day 6 with ECM shows SW'lies for all with a trough over Northern
Ireland and western Scotland. On day 7 strong to gale force
SW'lies cover the UK, with a shallow low over the Western
Isles.
On day 6 with GFS a trough lies to the west, with strong to
gale force southerlies as a result. The trough moves eastwards
on day 7, heralding lighter (but much coler) WSW'lies and
SW'lies.
Looking
further afield
On day 8 with ECM a deep low lies to the north, leading to
strong to gale force SW'lies. A ridge covers the North Sea
on day 9, with a mixture of southerlies and SSE'lies across
the UK. Southerlies persist on day 10 as a low deepens near
Iceland.
GFS brings low pressure over the North Sea on day 8, with
NW'lies for all. Day 9 sees a ridge over England and Wales,
with SSW'lies elsewhere. On day 10 there are further SSW'lies.
Ensemble
analysis (http://91.121.94.83/modeles/gens/graphe_ens3.php?x=306&ext=1&y=141&run=18&ville=Londres)
The ensembles continue to show a zonal "sine wave"
pattern.
In summary...
Low pressure will be close to the UK during the middle of
next week, with strong winds and rain likely across the UK.
The exact timing is hard to pin down, however, as the models
differ greatly regarding cyclogenesis and track of the lows.
