Indeed thanks. And as I get up too late it's always interesting to
compare you report with the later model runs to see how things have
evolved. I wouldn't even want to imagine how many 1000s of man hours
you have put into these reports!
Thanks again.
Alan
On Dec 10, 5:06*am, "Darren Prescott" wrote:
?Today marks the 9th anniversary of these model discussions - they started
as a look at the chance of a snowy Christmas back in 2001. The first post
can be seen on Google hehttp://groups.google.com/group/uk.sc...read/thread/61...
Thank you to all readers over the years!
Here is a summary of the NWP output for noon on Tuesday.
Issued 0501, 10th December 2010
The models are split today. GFS keeps things much as it has for days, with a
strong NW'ly flow over the UK during the latter half of the week and an
increasing risk of snow both from showers over exposed coastal areas and
from troughs moving south. ECM offers an alternate solution, with the
original blocking high moving west and a new high setting up in the vicinity
of Scandinavia, with cold easterlies setting in (and an increasing risk of
snow in the east). Either way will bring cold weather for the UK, but the
areas affected by snow would be different in each case. At the moment the
GFS scenario has the most support model-wise but it wouldn't be out of the
question that ECM ends up being correct.
Analysis and evolution to T+120 via GFS
Westerlies cover the UK, with high pressure to the south and southwest of
the UK. Tomorrow the high rotates, bringing light winds to Wales, Northern
Ireland and SW England. Elsewhere winds are WNW'lies, followed by NNW'lies
for most on Sunday as the high declines to the NW. The high builds again on
Monday, moving to cover Scotland. Northern Ireland lies under SE'lies as a
result, with NE'lies elsewhere.
T+120 synopsishttp://www.wetterzentrale.de/wz/pics/Rtavn12014.pnghttp://www.wetterzentrale.de/wz/pics/Rtavn1201.pnghttp://www.wetterzentrale.de/wz/pics/Rukm1201.gifhttp://www.wetterzentrale.de/wz/pics/Recm1201.gifhttp://www..wetterzentrale.de/wz/pics/Rjma1201.gif
The jetstream chart shows a diffluent block over the Atlantic with the UK on
the warm side of the jet. The jet is exceptionally strong over the Canadian
Arctic and Greenland. At the 500hPa level there's an elongated high
stretching from Greenland SE'wards towards the UK, with a trough over the SE
of the UK. The upper flow is NNE'ly as a result, whereas MetO shows
northerlies aloft with a ridge to the west. ECM shows upper northerlies too,
with an upper ridge west of Ireland. GEM shows an upper trough over the UK,
with cyclonic northerlies aloft. JMA has NW'lies aloft with an upper high to
the NW rather than a simple ridge to the west.
At the surface, GFS brings northerlies with a large high to the WNW.
Southern England lies under NE'lies due to a shallow low over France. MetO
has NNW'lies for all with a high to the west, while ECM has a high over
Ireland and NNW'lies over the UK. GEM brings light winds due to a col, while
JMA has a col over England and Wales and northerlies elsewhere.
Evolution to T+168
ECM shows high pressure over England and Wales on day 6, leading to SW'lies
elsewhere. Day 7 sees southerlies for all as the high moves eastwards.
GFS has NW'lies over the UK on day 6 as pressure remains high to the NW.
There are further NW'lies on day 7.
Looking further afield
On day 8 ECM brings SE'lies as pressure builds strongly over Scandinavia.
The winds become ENE'lies on day 9 as the high continues to build and on day
10 NE'lies and ENE'lies cover the UK as the high builds to over 1055hPa west
of Scandinavia.
Day 8 with GFS brings yet more NW'lies as pressure remains high to the west
and NW. A trough moves southwards on day 9 and on day 10 low pressure lies
to the south, with easterlies and NE'lies over the UK.
Ensemble analysishttp://www.meteociel.com/cartes_obs/gens_display.php?ext=1&x=306&y=14...
The GEFS continues to show a milder weekend followed by prolonged cold.
ECM ensembleshttp://www.meteogroup.co.uk/meteo/eps/ensemble-tt6-london.gif
The ECM ensembles haven't updated since yesterday morning.