Model Output Discussion 13/11/13 >

[Summer Sun]

Latest from Gibby

 

All models show a NW flow over the UK backing more towards the West over the next 24 hours as a ridge crosses the UK from the West attached to a High pressure area to the SW. Troughs will be held at bay for a day or so which will mean a lot of dry if rather cloudy and benign weather is likely over the UK until later on Saturday. A front then slides South over the UK bringing occasional rain and will maintain temperatures close to average for that point in time. Over Monday another more active cold front brings a band of rain too but this time becomes followed by very much colder weather with Northerly winds and wintry showers spreading across Britain on Tuesday.

 

GFS then shows cold weather setting in across the UK for a good portion of the rest of the run with a NE feed of raw winds across Southern Britain bringing rain and sleet at times and snow on the highest hills. Further North though the snow level will be lower the weather will generally be drier but no less cold with widespread frosts by night. At the end of the run the weather shown is still cold under a slack flow with Northerly winds and wintry showers near the coasts but a lot of dry, cold and crisp weather inland.

 

UKMO tonight shows a cold NNE flow across the UK with wintry showers almost anywhere but more especially in the East. Frosts at night will become widespread. The NW may see some freezing fog patches later as a ridge moves in and winds fall light here.

 

GEM shows very cold weather developing from the middle of next week with a broad scale Easterly flow dragging cold and grey conditions across the UK with rain and sleet at low levels and snow over quite modest elevations. The most precipitation will be towards the SE with all areas becoming calmer but still cold, frosty and possibly foggy by term.

 

NAVGEM shows complex Low pressure over the UK after the introduction of cold weather by the middle of next week. This then slides to the South with a raw and strong Easterly wind. Rain, sleet or snow will feature heavily over England and Wales with any meaningful snow reserved for the hills of the North. The far North and west could well become dry and cold away from North Sea coasts.

 

ECM shows cold weather arriving from the North early next week with High pressure soon developing to the North and setting up a very cold ENE flow across the UK by the end of the week. With such cold air and relatively low pressure wintry showers will occur quite widely especially near North sea coasts though inland it could be mostly dry. Later in the run Low pressure return North from the South cutting off the cold feed from Southern areas and returning the South of the UK slowly but surely into a very unsettled and slightly on the chilly side period with rain or showers at times and snow on the highest ground and in the North.

 

The GFS Ensembles on the face of it look nothing spectacular for cold lovers given the synoptics shown. However, they are only telling half the story with synoptics to die for from some members of the pack tonight. Nevertheless the definitive is that the weather is going to turn cold with some sleet or snow for some especially with elevation. However, away from elevation widespread snowfall would be unlikely with borderline uppers for much of the time.

 

The Jet Stream shows the flow riding high over the Atlantic before plunging South over the UK early next week. The flow then begins to settle at a latitude South of the UK with a trajectory such that prolonged and cold spell is possible for the UK.

 

In Summary a cold spell is on the way and no doubt some snow will fall in places over next week. The longer term synoptics differ from model to model and there is still some way to go before longevity of such a spell becomes guaranteed. With ones feet firmly on the ground snowmageddon is certainly not an option with cold rain and sleet more likely in the South though with falling snow possible over the higher hills. Further North the chance of settling snow increases with possible disruption at times to high level routes. Looking further out my suggestion of a foggy and frosty spell that I indicated this morning looks a little less likely tonight with perhaps more of a suggestion of the Low pressure to the South edging North again and cutting off the cold feed maybe more likely. However, all this is sheer speculation and I must concede and understand the excitement through what is dream synoptics thrown out by the models at the moment. It is a shame it's just two months too early to give what would be a memorable cold spell should it of evolved as shown then.

 

http://www.norton-radstockweather.co.uk/Model-Analysis(2859336).htm

[essexweather]

12Z ensembles from Euro now up: http://www.essexweather.com/outlook.html

 

Would still urge on the side of caution for those wanting snow South of the Wash... 850s remain marginal, especially along coastal areas.

 

Only 7/50 ECM members have snowfall accumulation for the Home Counties as an example (and that occurs between 00Z and 06Z midweek)

 

Still trending the right way with each run though

Edited November 14, 2013 by essexweather

[Snowmadsam]

Feel free to discuss....negative NAO signalled here

 

[stewfox]

. However, all this is sheer speculation and I must concede and understand the excitement through what is dream synoptics thrown out by the models at the moment. It is a shame it's just two months too early to give what would be a memorable cold spell should it of evolved as shown then.

 

http://www.norton-radstockweather.co.uk/Model-Analysis(2859336).htm

 

Two months ? there was a suggestion the potential could be similar to Nov/Dec 2010. if the models do reload with increasing cold incurrsions surely better to start at the beginning of winter then nearer the end ??

[Gibby]

Two months ? there was a suggestion the potential could be similar to Nov/Dec 2010. if the models do reload with increasing cold incurrsions surely better to start at the beginning of winter then nearer the end ??

Yes but synoptics such as being thrown out at the moment are notoriously rare in the UK and I was just highlighting that they may not be seen in the depth of this Winter. That has no bearing however, on how I feel the Winter as a whole will pan out. The most important word in your post was 'if' and that is a very small word with a very big meaning.

Edited November 14, 2013 by Gibby

[bluearmy]

12z naefs update - yes the 12z has just updated (earlier charts were the 00z).  the weak anomolys in fi firming up to be high to our nw stretching across n america whilst our trough reaches out ne to link up with the siberian vortex.  massive spread across the whole NH does lead to uncertainty but the mean chart at day 10 is quite something for november and that week 2 anomoly developing should mean we see colder uppers feeding down to our east.  massive spread though and noaa cpc are not confident with their output.

[Summer Sun]

Good agreement on the NAO staying negative towards the end of the month tonight

 

[shaky]

12z naefs update - yes the 12z has just updated (earlier charts were the 00z). the weak anomolys in fi firming up to be high to our nw stretching across n america whilst our trough reaches out ne to link up with the siberian vortex. massive spread across the whole NH does lead to uncertainty but the mean chart at day 10 is quite something for november and that week 2 anomoly developing should mean we see colder uppers feeding down to our east. massive spread though and noaa cpc are not confident with their output.

thats a brilliant update bluearmy!!one thing I have noticed is that on each update your giving on the naefs it seems to be that the signal for high pressure to our north or northwest seems to be getting stronger am I right in saying.

[Biggin]

"The flow then begins to settle at a latitude South of the UK with a trajectory such that prolonged and cold spell is possible for the UK." Ta Gibby all I need to know.

[legritter]

Evening all ,what a  good model run and the first one viewed on my new computer wind 8 .cold weather fans must be over the moon,but we must stay in control as  we know it could all be gone in a flash later in the far outlook .but certainly a good start .i would say looking at current charts many with a bit of elevation and luck could do well after late next tuesday .Fax  charts will be our best quide for finer detail as each day will present new features with cold air coming across warm sea s .certainly an unusual set up for now ,may it continue .tonights ECM came as a surprise as i clicked on last  frames first ,old computer in retirement ,take care and lets enjoy that crisp sharp arctic air .

[Met4Cast]

Very slightly more amplified so far on the 18z run, good start

[radiohead]

The colder air arrives in Scotland and NI a little faster on the 18Z GFS.

 

[bluearmy]

thats a brilliant update bluearmy!!one thing I have noticed is that on each update your giving on the naefs it seems to be that the signal for high pressure to our north or northwest seems to be getting stronger am I right in saying.

 

thats a fair assessment out to day 10. thereafter, i wouldnt want to pick a horse other than to say it looks like all options are cold.

[Mair Snaw]

You can almost hear everybody taking in a deep breath as the pub run starts to stagger out.....i really do hope its been at the bar since lunch time....

[Met4Cast]

More WAA into Greenland on this run. The 18z has also developed a shortwave running Southwards, delays the cold air slightly but would increase the chances of back edge snowfall for most of us

 

[SMU]

Were already home & dry on the 18z for phase 1 cold & the secondary ridging.

 

good Stuff. poss lots of snow over the midlands & SW at day 5 on this run - ( tues)S 

[Mucka]

Plenty of snow for Northern/Central England if this were to verify.

 

[I remember Atlantic 252]

Looks like a polar low on Tues 19th, but isn't, still feel any snow for the south would be over 300m

[Cheshire Freeze]

Oh my, come to papa

 

 

[cheese]

Indeed, CC. GFS has been consistent for a few runs now with the idea of a notable snow event for northern England, but now shows snow for Wales, parts of the Midlands and SW England, too.

[damianslaw]

The models are certainly showing unusual synoptics for the time of year - akin in many respects to late November 2010. This is the time of year when weaterlies begin to reach their yearly maxim. However, there are significant changes taking place in the upper northern hemisphere atmosphere - notably strong pressure on the polar vortex helped largely in part by the long presence of the aluetian high - which is causing a split in the vortex and more importantly weakening it considerably allowing mid atlantic heights to ridge up to Greenland and conversely sending the polar front jet on a crash course with southern europe - you can't ask for much better foundations for a solid cold outlook for the UK.

 

Too early to be speculating on where snow will fall and how much, but as others have said, uppers could be very marginal in southern parts, and reliance will be placed on evaporative cooling. The north however, will be under colder uppers, and away from the coast I would imagine snow will settle quite readily.

 

The general theme as I see it is for heights to remain very strong to our NW next week, with a significant trough to our SE linking into scandi.If such a synoptic holds, then ice days are very likely in the north under stagnant cold air.

 

After a very lengthy period of above average temps preety much since late June barring the odd cooler blip notably in mid Sept, we are about to see our first spell of appreciably below average temps for 5 months.

 

It looks like we will see yet another November with notably cold conditions during the latter part, something we have seen occur in 3 of the last 5 Novembers, 2010 most notably so, but 2008 and last year also delivered quite cold weather at times in the latter stages.

[Mair Snaw]

Oh my, come to papa

 

 

IMBY yes please.....that would do for me..really good charts these..just gotta get them closer to t0...

[weatherguy]

Feel like a broken record each undercutting low scenario, but briefly...

 

Cold air with atlantic moisture added is never going to bring record breaking minima, but it does provide ammunition to see snowfall rather than a bitter HP dominated scenario.  Remember: easterly airflow with uppers below 0C is usually good enough for snow, so need to worry about us ending up with cool and damp conditions if that's the case!

 

The ECM does look marginal in this regard but would still be just cold enough in my opinion, perhaps not so for the far south mind, and perhaps not cold enough for snow throughout, but cold enough all the same for most places to see snow at one stage or another.  However, reload inbound after +240

Edited November 14, 2013 by weatherguy

[Frosty.]

<p>Thought I would mention this, I know it's been mentioned already but i'm adding the temperatures...this from the GEFS 12z control run is just mind blowing, it would be hard to top this, sub zero and blizzards..what a start to winter that would be..2010 couldn't even match these charts, they are off the scale..and finally, this from darren bett....great chart to see, finally we have something for coldies to cheer.<img alt="" class="bbc_emoticon" src="http://f1.nwstatic.co.uk/forum//public/style_emoticons/default/drunk.gif" title="" /> <img alt="" class="bbc_emoticon" src="http://f1.nwstatic.co.uk/forum//public/style_emoticons/default/clapping.gif" title="" /></p>

[SMU]

GFS at 156 - with High to the SW of Iceland & a huge - PNA ridge in the SE states-

 

I would hazard a guess the high will flatten into scandi by 180-

 

The 2 highs join at the 200 Mark & set up a retrograde Greenland block for mid 2' hundreds....

 

S