Model Output Discussion - 14th - 20th November

[wolvesfan]

Morning all,

Gfs not looking good for us cold lovers this morning,after a brief fly in the ointment next weekend the pattern resets with high pressure centred slightly further SW.end result SW airflow across the uk for the foreseable.

[Costa Del Fal]

The 850's on the 06z operational were a mild outlier for a time later in the run. The mean looks quite firmly in the range of 0 to -5c 850's beyond next weekend. Its likely to change but I think at least a much more seasonal feel to things beginning soon. Beyond next week Max temps look like they will be firmly below 10c and perhaps closer to 5c by day.

Overall, there is potential for short spells of interest and certainly more interesting than the endless southerly's we have experienced this month and last.

[weathe20]

Seems a pattern change is on the way, with the atlantic pushing that Euro high out the way. Temps returning back to average values with the chance of some wintryness over Scottish mountains. That kind of sounds like a normal UK winter to me?? This pattern change may lead to something more interesting for cold lovers down the line, but nothing exciting in terms of any proper cold. This new pattern could well be set for a number of weeks, not good with only 14 weeks of winter left!

[nick sussex]

We would be looking for pressure drops in the med , which would allow the westerly/ northwesterlies too pull in a more northely component . If we don't any real cold is likely to remain north of uk as the high acts as a block ? Incurrsions bounce off the high ?

There are certain essentials that are needed for a more cooler type of zonality and thats the displacement of the high west into the Atlantic and pressure to fall in central Europe.

In terms of a more northerly component you'd generally need the pattern even more amplified, cooler to colder zonality that sticks needs higher pressure near Svalbard to force the jet on a nw/se tilt.

The output today looks very normal standard fare when you have low heights to the north and Euro high to the south, in a nutshell unless that Euro high gets pulled west into the Atlantic then its very difficult to get even PM incursions apart from in the far north and even then the forcing of the PV will eventually tilt the jet unfavourably.

Edited November 20, 2011 by nick sussex

[Richard Fearn]

hi guys back for the winter, by the looks not looking good for some cold weather at the moment, im not really that good reading charts but i know from last year that the 528 dam was a part of our snowy winter, i looked at the chart and seems to make a appearance over the uk at the end of november/ beginning of december would this be a player in bringing us some wintery conditions or any influence in cold weather

[Backtrack]

hi guys back for the winter, by the looks not looking good for some cold weather at the moment, im not really that good reading charts but i know from last year that the 528 dam was a part of our snowy winter, i looked at the chart and seems to make a appearance over the uk at the end of november/ beginning of december would this be a player in bringing us some wintery conditions or any influence in cold weather

Sure it would, but such a shame the models are only showing brief Northerly topplers (24-48 hour shots) or brief incursions from the NW. Basically equating to snow over hills and mountains in the North.

Just keep hoping and our time will come.

Edited November 20, 2011 by Backtrack

[Thundery wintry showers]

In frontal battleground situations between Atlantic air and continental air, snow can fall to low levels in 528 dam air or even higher, but in showery polar/arctic maritime setups, or those easterlies with snow showers generated over the North Sea, 522 dam is often a better benchmark.

Meanwhile, today's models continue to show a shift towards zonality but it's notable that the colder polar maritime type of zonality is mostly locked out on the wrong side of T+168, so for the reliably-foreseeable future, high pressure continuing for two or three days and then a fair amount of tropical maritime south-westerly types, with dull wet weather in the west but some dry sunny interludes in the east and south.

[Richard Fearn]

Sure it would, but such a shame the models are only showing brief Northerly topplers (24-48 hour shots) or brief incursions from the NW. Basically equating to snow over hills and mountains in the North.

Just keep hoping and our time will come.

thanks backtrack will be keeping a eye out for a more sustained 528 dam

[TonyH]

Guide to the week's weather for west Wales and the Midlands for Monday 21st to Sunday 27th November:

Headline: Mostly mild; some rain at times, but not so much for the Midlands again

In spite of some of the sensationalist 'forecasts' in the media this Autumn of impending snow and -20c temperatures, we have enjoyed one of the mildest most benign Autumn's on record (lesson: ignore the newspaper headlines!). The continued Euro blocking means that Warwickshire is still in with a chance for the driest year on record, provided only 2 inches more rain falls during the last 6 weeks of 2011.

Monday may be another foggy start in the Midlands, most of us then in for a cloudy mild day. It stays dry for the Midlands, while a little rain or drizzle breaks out over west Wales, especially later. This is brought by a slow moving trough which during Tuesday gradually edges east while weakening. Rain at times Monday night and early Tuesday for Wales, brightening in the afternoon, while for the Midlands Tuesday is a largely cloudy day with a little rain possible and mild again.

The trough clearance later Tuesday brings a chilly night with frost distinctly possible for many,and below zero for some of us. A ridge of high pressure remains close to the south through Wednesday so a mostly dry day with the best of any sunshine for the Midlands, while west Wales could get a little drizzle by evening from the next Atlantic front. The influence of the high should keep the Midlands dry and bright again on Thursday, and a very mild day up to 14c here. For west Wales a largely cloud day, and with a vigorous Atlantic system edging into Ireland it looks like it will turn wet and windy during Thursday, although the worst perhaps holding off until evening.

This front gets a move on through all parts Friday, and as a result rainfall amounts may disappoint yet again in Warwickshire! Friday then a bright, breezy day with a few showers out west. A cooler day too, temperatures close to the late November average of 9 or 10c.

Next weekend sees the westerly flow continuing so unsettled and windy at times, with further spells of rain, with the heaviest for west Wales. Temperatures average to mild.

For supportive charts:

http://forum.netweather.tv/topic/69041-wales-regional-weather-discussion/page__st__120__gopid__2162076#entry2162076

[Backtrack]

thanks backtrack will be keeping a eye out for a more sustained 528 dam

Most welcome.

As TWS has said above though, in the type of set up we are about to endure if the models turn out correct, a DAM lower than 528 would be more conductive to snow at lower levels.

[Richard Fearn]

In frontal battleground situations between Atlantic air and continental air, snow can fall to low levels in 528 dam air or even higher, but in showery polar/arctic maritime setups, or those easterlies with snow showers generated over the North Sea, 522 dam is often a better benchmark.

Meanwhile, today's models continue to show a shift towards zonality but it's notable that the colder polar maritime type of zonality is mostly locked out on the wrong side of T+168, so for the reliably-foreseeable future, high pressure continuing for two or three days and then a fair amount of tropical maritime south-westerly types, with dull wet weather in the west but some dry sunny interludes in the east and south.

looks like i need to get my head round these charts think ill wait for the 18z and get stuck in

[Frosty.]

Even if the Gfs 06z verified, the uk still has a colder and very unsettled spell to look forward to, ok, no widespread snow or frost but at least a change from the current 15-16c weather which has dominated large chunks of november so far, a cooling trend to average is already in the bag but can we take the next step to a cold snap? the 00z says yes, the 6z says yes for a while and then gives up and the milder air is back in FI but snow will fall on northern hills from midweek onwards and some frost can be expected where skies clear but also some milder, wet and windy spells.

[Summer Sun]

Looking like this week will be another mild at times and dry one for the South East whilst the north west will turn wet and very windy with severe Gales by mid week by Friday the winds will ease and snow should become widespread for the mountains and high ground in Scotland. Frosts should also be widespread for all but the South East for a few nights this week.

The main point for the week is those that need the rain sadly won't see much and a few storms should hit the North west with snow on Friday. This week should have something for all.

Edited November 20, 2011 by Gavin D

[Glacier Point]

Id be surprised if the models start raising heights over finland- thats probably the last place thats going to get any height rises post day7/8, the vortex is getting shuted S.S.E out the pole into Scandi & heights will be sub 500DAM- *IF* the proposed pattern does set up then taking today as day 1 then we are at least 17-21 days away from heights raising in that area-

S

Last 3 GFS runs have started to develop this idea of the longwave trough starting to elongate in our locale and one would assume begin to disrupt just like the ones before, which I think helps to build the ridge over Scandinavia in time. 06Z GFS ensemble mean strengthens the mean height anomaly as the run progresses from t348 through t384. At that range, a strengthening anomaly is noteworthy.

[summer blizzard]

Progress seems definitely to have been made.

GEM, GFS and ECWMF all show a polar maritime shot over the UK by day 6 or 7 (lets hope we do not see the downgrade).

GFS and E3CWMF also show a northerly toppler at day 10.

Ensembles are generally undecided past day 5 but the mean is below average from the 29th.

In summary, snow will be unlikely unless you live above about 500 meters and it looks too windy for frost. That said, the flow looks fairly clean and showery due to the polar element so it will feel and actually be on the chilly side.

[Frosty.]

The main point for the week is those that need the rain sadly won't see much

Indeed, this is very serious, there is a drought in parts of southern and eastern england due to a very warm and mainly dry autumn and they need heavy persistent rain to start filling the reservoirs, the models at least indicate some wet and windy spells to give those areas some much needed water.

[Snowmadsam]

Last 3 GFS runs have started to develop this idea of the longwave trough starting to elongate in our locale and one would assume begin to disrupt just like the ones before, which I think helps to build the ridge over Scandinavia in time. 06Z GFS ensemble mean strengthens the mean height anomaly as the run progresses from t348 through t384. At that range, a strengthening anomaly is noteworthy.

What does this mean? (sorry i'm kinda new to this thing)

[summer blizzard]

What does this mean? (sorry i'm kinda new to this thing)

Basically that in the long term, the Euro High will be back.

[Snowmadsam]

Basically that in the long term, the Euro High will be back.

oh... LOL

[Frosty.]

Basically that in the long term, the Euro High will be back.

The euro high will bring cold and frosty, foggy weather in winter so I hope it does come back!

[rich1]

The euro high will bring cold and frosty, foggy weather in winter so I hope it does come back!

positioned correctly it can, and if somehow we could get the thing to be a bit further north it may turn in to something rather better. But at this time its an estimate, not as I said a fait accompli. The last chart on the GFS showing it is an outlier as well

a cold HP spell around Xmas I would take actually at this point, but my feeling for December echoes with BFTP, I think it will be a bit more variable on the whole. There have been a scatter of scenarios modelled an FI is retreating to an earlier period than in recent weeks, and December is still 10 days away so there is still a lot of time left to run. A december like last year is not likely but that doesnt mean that a sub-average December is by any means impossible still

Edited November 20, 2011 by rich1

[Nick L]

The euro high will bring cold and frosty, foggy weather in winter so I hope it does come back!

Not necessarily, it depends where it's positioned really. If we're on the northern flank of it then surely we'll just end up with more mild muck again?

[shedhead]

About the only thing guaranteed with a Euro High is Kent will see more overnight frosts than Kirkwall, if there are any of course. As others have said, it's all about the positioning, but wherever it sets up the only areas likely to be average or below are central and eastern England - elsewhere above average or even mild is again the most likely outcome.

Edited November 20, 2011 by shedhead

[ribster]

Yesterday ECM was the model of choice for cold, today it's not, GFS visa versa and tomorrow we'll probably switch back around again. Far better to take a broader view of things imo, rather than jumping on the run that best fits your desires and that broader view is cooler, more unsettled but with absolutely no sign whatsoever of either deep or sustained cold - still.

Not sure that we regularly get deep or sustained cold in the uk do we, so wouldn't really expect any models to be showing it? In my lifetime I can count on one hand how many periods of deep and sustained cold we have had, one of those was last year. However, if you're looking at the models more realistically, then frost, fog, some sleet and perhaps some snow for higher ground is on offer.

[shedhead]

I wasn't looking for deep or sustained cold, just the signs of it, as I clearly stated. Moreover I think it's fair to say that at this time last year there were very clear signs of deep and sustained cold and it duely delivered, so yes sometimes the models do show it - or at least it's clear potential. At present there is no sign or no potential whatsoever, unless of course you cherry pick the runs as many do.

Edited November 20, 2011 by shedhead