Model Output Discussion 13/11/12 18Z onwards

[fergieweather]

Makes sense, though they seemed more bullish at the start of the month in regards to cold.....I remember the further outlook being more committed in terms of end of month cold and of course their video highlighting this liklihood turned a few heads. This seemed to be based on the EC32 and I'm intrigued to what they have seen to slightly back off the scenario to a point that they appear less confident of potential synoptics than they were 2 weeks ago.

They currently stick with the 30% PROB scenario for colder, dry / blocked into the 15d trend period. That's remained consistent recently. However, they note that it remains a continued theme, so they're in no way disregarding it. Doubt much stock given to GFS way into FI however - they'd be forever chasing their tails if they bothered with that stuff. They stick with ECM output (and MOGREPS of course) as the primary driver for the longer MR in any case above anything churning-out from the American model.

Edited November 16, 2012 by fergieweather

[Liam J]

They currently stick with the 30% PROB scenario for colder, dry / blocked into the 15d trend period. That's remained consistent recently. However, they note that it remains a continued theme, so they're in no way disregarding it. Doubt much stock given to GFS way into FI however - they'd be forever chasing their tails if they bothered with that stuff. They stick with ECM output (and MOGREPS of course) as the primary driver for the longer MR in any case above anything churning-out from the American model.

Thanks Ian, your input into this thread is very much appreciated, certainly something to learn for many people viewing the MOD taking note of your posts, especially regarding the various insights into whats happening down at Exeter.

Edited November 16, 2012 by Liam J

[AWD]

The GFS is a lot more amplified than the ECM at T168;

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=168&code=code&mode=0&mode3h=0&runpara=0&carte=1

http://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=1&map=1&type=0&archive=0

with a much more notably trough over the UK & better ridging than the ECM.

[A Winter's Tale]

Good evening everyone. The theme for tonight is cloudy, murky and damp conditions with showers in north western areas whilst a weather system moving in from the south west later this evening bringing widespread rainfall to the south west Wales and into the north east. This particulary feature should clear into the north sea but the cold front should slowly make it's way further south and east bringing some light rain overnight to Wales and south western and northern parts of England. Ontop that there could be some fog patches in southern parts of England and possibly some drizzle. It should be a cloudy night for England, Wales and eastern Scotland but much of Ireland and Scotland in general should have some clear spells overnight aswell as showers that should begin to turn wintry over the high ground as cold air follows the front. Tonight's minimum values ranging between 4 and 12C. The high pressure over the continent that has influenced the weather this week is being pushed away further east as colder and fresher air moves in thanks to low pressure centred near Iceland.

Saturday morning should start off grey across much of England with some light rain moving south eastwards with the weather fronts whilst in Scotland and Ireland much clearer, fresher and colder weather should follow with showers in western areas and some of the precipitation wintry even to some lower elevations. However the clearer and colder conditions should spread into Wales and northern England during the afternoon - the south east may hang onto the cloud cover and some rain later into the evening - and in north western areas there'll be further showers that will be wintry on the high ground. Maximum temperatures much colder than of late with values typically 5 to 8C but possibly still into double figures in southern areas.

During Saturday night we finally lose the fronts and should be left with a widespread frost and clear skies. There should still be some showers in north western areas and these could be wintry on the high ground but all in all Saturday night is looking fine and crisp in comparison to what we've seen in this typically autumnal week as a brief ridge of high pressure develops over the British Isles - particulary in the south. Overnight lows 0 to 5C.

Sunday should start off crisp and sunny and indeed it is looking like a promising and cold day with showers restricted to very north west of Scotland and these could still be wintry. There should be widespread sunshine under this ridge of high pressure. Maximum temperatures of 4 to 9C.

However, as you can see in the chart above, an area of low pressure is set to move in from the south west and bring wet and windy weather later on Sunday as the wind direction changes to a milder south westerly. Sunday night could see lows of 2 to 8C, but it's looks like there could be a lot of wet weather around - especially in western areas.

Monday could be a mostly cloudy, unsettled and wet day for many areas but Ireland could at least stay drier aswell as some eastern parts of England. A much milder day with the south westerly flow, possible maximum temperatures of 10 to 13C.

There may be less rainfall during Monday night but skies should remain overcast. Drier conditions for the bulk of England and Scotland but southern parts of England, parts of Ireland and the far north of Scotland could be see overnight rainfall. Minimum temperatures of 5 to 11C.

There could be some heavy and persistent rainfall for southern areas on Tuesday and also the possibility of some rain around the Irish Sea. North western areas could stay drier. Another mild day with possible highs of 8 to 13C. Low pressure set to be placed west of the British Isles whilst high pressure remains to the east of Europe.

The milder southerly winds could be pushed further east during Tuesday night and replaced by cooler and fresher winds off the Atlantic. Currently, Scotland is shown to have some heavy overnight rainfall and some fronts could be close to Ireland whilst skies could clear in southern parts of England and Wales. A cooler night with lows of 3 to 9C.

The period of Wednesday to Friday, the anticyclone remains further east of the British Isles whilst low pressure is situated closely to the west. Wind directions could fluctuate as low pressure is shown to move closer to the British Isles later in the week and there could be some temperature variations - on the cool side in northern areas but temperatures possibly into double figures at times in southern areas. With such changeable conditions there could be quite a bit of rainfall to times - possibly some quite active weather later next week. But a lot of the specifics depend on the relation between the anticylone to our east and the low pressure, if the anticyclone moves futher east then this would have a large impact on the distribution of rainfall and temperatures. If low pressure moved over the British Isles then we would lose the southerly flow and conditions would be unsettled and changeable for all areas. At this stage, the theme is for high pressure to the east and low pressure to the west, but the details at this stage will continue to vary and this would have impact on the end result.

In the chart below, the area of high pressure centred in the Atlantic a lower latitude ridges further north as low pressure is shown be located around the British Isles and the anticylone remains futher east.

The high pressure over western parts of Russia is pushed further east during the runs late in the period. Also high pressure shown to be close to or even over the British Isles for a time.

GFS 12Z:

ECM 00Z:

And the final chart of the GFS 12z shows high pressure further west of the British Isles with a northerly air mass over the British Isles. During the past few days, in FI there has been a trend for blocking. This remains a possibility but I'll await many more days of model watching to have a somewhat clearer idea to what sort of trend we have for synoptics in the NH later this month and we all await further developments of factors and variables that influences the weather. This should progress nicely - but slowly - during the many, many days to come.

GFS Ensemble Charts:-

Aberdeenshire T850:

London T850:

Reykjavik, Iceland Air Pressure:

Oslo, Norway Air Pressure:

[Cheshire Freeze]

The GFS is a lot more amplified than the ECM at T168;

http://www.meteociel...npara=0&carte=1

http://www.meteociel...ype=0&archive=0

with a much more notably trough over the UK & better ridging than the ECM.

Yes was just thinking the 168hrs doesn't look so good (if you're after cold). Rather annoyingly there seems to be a trend to disrupt the PV in a way which still manages to leave a segment towards Greenland which delays and blocking in that area! Sod's law I'm afraid.

Edited November 16, 2012 by CreweCold

[bluearmy]

note the 12z ecm brings the shallow depressions from the se seaboard into contact with a cold shortwave spat out by the vortex. the mix of airmasses winds up the depression and will give the jet a kick.

Yes was just thinking the 168hrs doesn't look so good (if you're after cold). Rather annoyingly there seems to be a trend to disrupt the PV in a way which still manages to leave a segment towards Greenland which delays and blocking in that area!

thats nothing new for us cc. we've seen that many times though usually at the back end of winter when we're chasing something cold to make up for whats been before.

[nick sussex]

It looks like its that time of the year when we will once again be discussing shortwaves and trough disruption!

Could be another February 2012 revisited with the ensuing drama as the models disagree where to eject the shortwave.

Overall given where the PV is expected to set up then its really going to have to be an initial east/ne flow, hard to see any northerly appearing unless the pattern retrogresses later.

[Cheshire Freeze]

thats nothing new for us cc. we've seen that many times though usually at the back end of winter when we're chasing something cold to make up for whats been before.

Yes and this is the reason I refuse to be taken in by hype. We tread very fine lines in getting cold to these shores Dec/Jan 2009/10 and Dec 2010 were anomalies in this sense as everything that could go right, did.

[Cheshire Freeze]

This is like pulling hens teeth. ECM 240 is excellent once again...

[AWD]

ECM finishes with a rather intense vortex over Greenland helping create some mega depressions.

http://www.meteociel.fr/modeles/ecmwf.php?ech=240&mode=1&map=1&archive=0

Still chilly over the UK in more benign conditions, just not the elusive cold.

(Beat me to it CC)

Edited November 16, 2012 by AWD

[ChartViewer]

Worst run for retrogression or any hlb for a while.....Pattern is flattened and maybe the Vortex is just too strong for any retrogression to take place.................Im still thinking all models are struggling with patterns around 27th Nov to Dec 1st and subsequently all runs right now are completely different......Suspect T144 UKMO time to get involved....

[Geordiesnow]

Its amazing reading this thread because you would think there is a cold shot could be in the pipeline in the very near future yet the trends are clearly for Atlantic based weather with winds coming from a SW'ly direction with little noticeable blocking on offer, temperatures are showing to be near average with unspectacular upper air temps to what you expect from a SW'ly direction.

Reading this thread these last few days has been repetitive, cold shots/blocking being discussed in FI(past 200 hours) and the reality shows very minimal signs of much blocking showing on the output post FI, infact, I have seen little signs of any cold proper shot even in the FI charts from what I seen. What has been consistent on the outputs however is the split PV over the Arctic thanks to height rises but I don't see any blocking effecting our weather for a good while yet.

Instead of the white stuff on offer, with the exception of the highlands/grampians of Scotland this weekend its going to be a very wet outlook for some parts of the UK it would look like and the potential for some gales for western facing coasts in particular at times so an autumnal outlook for sure. Flooding could very well be a possibility as well

Edited November 16, 2012 by Geordiesnow

[January Snowstorm]

A very tasty Scandy high setting up at 240hrs.

Steve M will be pleased though I have to wonder where does this leave GP's thoughts as he was pretty adament that height rises would be over Greenland / Iceland.

Still ECM screams of potential

[Cheshire Freeze]

ECM finishes with a rather intense vortex over Greenland helping create some mega depressions.

http://www.meteociel...map=1&archive=0

Still chilly over the UK in more benign conditions, just not the elusive cold.

(Beat me to it CC)

The 240 chart is awesome. one or two frames further and that PV would be nigh on non existant. WAA straight into the Arctic and looks like a complete PV split would ensue. Also look how the low is filling around Greenland between 216 and 240. 955mb to ~975mb.

Edited November 16, 2012 by CreweCold

[Methuselah]

I wonder if that bit of vortex over Greenland could become detached...What might that scenario lead to?

[Cheshire Freeze]

Still ECM screams of potential

It does.....some posters over on the other forum talking about the 240 hrs chart being dull, damp and cloudy. That maybe the case initially but sometimes it's better to look holistically rather than just take a chart at face value. I think the natural progression from the ECM 240 hrs chart would be anything but 'dull, damp and cloudy' and more 'cold, crisp and snowy'........that's mere conjecture at this point in time though

Edited November 16, 2012 by CreweCold

[ANYWEATHER]

Plenty of Potential from the ecm @240. East meets West! See where things go from here....

[Gibby]

Good evening. Here is my take on the 12zs tonight from GFS, UKMO and ECM for today Friday November 16th 2012.

All models show a similar pattern through the next 7 days. A complex trough is moving steadily in from the West replacing the dank and gloomy weather currently over the UK. As it goes a spell of rain can be expected for all and it will clear only slowly across England and Wales through tomorrow. Following on behind will be clearer and colder conditions with some wintry showers in NW Britain. A ridge of High pressure is shown to move East over the UK on Sunday with a fine and sunny day following over the UK through the day following a frosty night. On Monday and through the working week next week Low pressure becomes dominant to the NW of the UK with a broad and sometimes strong SW or South flow bringing relatively mild and unsettled conditions with spells of rain and strong winds at times to all.

GFS then shows Low pressure crossing slowly East over the UK at the end of the week and through the weekend with further rain at times in temperatures slowly falling as a more Northerly flow develops in the wake of the filling depressions departure. Through a good portion of FI High pressure becomes dominant elongating itself over the Central slice of the UK with generally dry and innitially quite cold and frosty conditions with some fog too before the infill of cloud rounds the top of the high and descends down over the UK later with a weak cold front sinking South over the UK brings in much colder weather to end the run with a wintry mix of rain, sleet and snow showers in cold Northerly winds.

The GFS Ensembles show a continuing cooling trend with the operational on the warmer side of the pack towards the end of the run with quite a bit of support for colder solutions in the latter end of the run. Rainfall amounts do decrease somewhat as we move through week 2.

The Jet Stream shows signs of sinking slowly South over the coming week to a position just South of the UK by this time next week in response to Low pressure moving over the top of the UK then.

UKMO at 144hrs shows a Low pressure belt stretching from the Norwegian Sea to the Hebrides. A mild and breezy SSW wind blows rain bearing fronts east and North over the UK at times.

ECM is very similar at 144 hours bringing the Low pressure areas across the UK in the following day, weakening in situ over next weekend. So following further outbreaks of rain early in the weekend these will give way to rather overcast, misty and gloomy conditions under slack pressure conditions on Sunday. The end of the run shows a complex and slack pressure gradient continuing over Britain with dull and misty conditions continuing with occasional pockets of rain in temperatures sliding off day by day.

In Summary the output splits itself into two halves tonight. The first week shows a typically mild and unsettled SW flow of winds with rain or showers at times for all. By next weekend things become more complex with a trend for High pressure to try and build over the UK from Scandinavia on ECM's output or rather later from the SW by GFS. Either way on the operationals setup a lot of cloudy and misty weather would develop with temperatures near to or somewhat below normal as a lot of cloud would be trapped over the UK thanks to the decaying Low's. GFS does show some encouraging signs towards cold at the end of their ensembles while the operational shows a wintry end to the run once more.

[chris55]

They currently stick with the 30% PROB scenario for colder, dry / blocked into the 15d trend period. That's remained consistent recently. However, they note that it remains a continued theme, so they're in no way disregarding it. Doubt much stock given to GFS way into FI however - they'd be forever chasing their tails if they bothered with that stuff. They stick with ECM output (and MOGREPS of course) as the primary driver for the longer MR in any case above anything churning-out from the American model.

That just about sums up all MO discussions on the weather forums!!!!! So much information available, probably to much to be honest, but I guess thats where the fun is for us internet model watchers. We can say what we see with no one to judge us, and occasionally we do out do the Met in the longer term.

[Liam J]

One thing I would be concerned about is the Azores high becoming a player which could introduce a long fetch SW'ly flow, GFS & ECM pretty much agree on this around T192. Again another 24hrs on in model watching and any potential hint of a cold spell is still very much locked away at the back of FI land. Much patience needed!

Some very wet & windy weather is still on the cards overnight Sunday into Monday, gusts in excess of 60mph likely through the Irish Sea and affecting N England and S Scotland - potential for some difficult conditions developing in theses areas.

[Snowy Easterlies]

is it me or does the PV seem to get stronger on every new run in FI, blocking still there but will it be strong enough ?

[andymusic]

That just about sums up all MO discussions on the weather forums!!!!! So much information available, probably to much to be honest, but I guess thats where the fun is for us internet model watchers. We can say what we see with no one to judge us, and occasionally we do out do the Met in the longer term.

we are all a bunch of "human computers" anyway churning out our own model runs from the available data - helping everyone to see the coming weather patterns - the more "computers" analyse the data - the more correct answers we eventually get!

[MR EXTREMES]

some intresting charts coming out but once again well into fi i really cant see how anything in fi is going to come into fruitation its almost like saying chelsea will win the champions league again and then half the team being sent of or banned.

possible it could happen but the likely hood it will pan out as the models are suggesting is really clutching at straws.

[SMU]

A very tasty Scandy high setting up at 240hrs.

Steve M will be pleased though I have to wonder where does this leave GP's thoughts as he was pretty adament that height rises would be over Greenland / Iceland.

Still ECM screams of potential

Evening Allthe 2 charts of the Day-http://www.meteociel.fr/modeles/ecmwf/runs/2012111612/ECH1-168.GIF?16-0http://www.meteociel.fr/modeles/ecmwf/runs/2012111612/ECH1-192.GIF?16-0ALSO UKMO ALLIGNED TO ECM at 144 identical-Sorry for people following the GFS- please read my late night post last night ( & JH) its PAP.The GFS cannot resolve undercutting until around 120 ( properly ) - Maybe the odd run here & there-The ECM has been all over this from the start forcign the energy to stall out towards Greenland-Tonights the colder runs are at 168 on UKMO & ECM- watch the day 7 ensembles for ECM.Nowts changed now for 4/5 days- & finally we have consistent traction through the timelines from 216 > 192> 168-144 will be the first chance tomorrow of seeing this TYPE of chart-http://www.meteociel.fr/modeles/ecmwf/runs/2012111612/ECM1-168.GIF?16-0This is the chart you will need to look for.Forget the I'm not happy, in fact I'm quite sad model in THIS TYPE OF SCENARIOAs for HP over greenland- thats at best +2 days after the scandi block through retrogression, so best estimates are still day 13.Summary-Day 8 is the first undercut, 9 & 10 sustains the block with uppers around -2 to -5c underneath-11-13 another retrogression west then possibly towards GH.S

[nick sussex]

I think the best that can be said about tonights output is shows some promise but must try harder!

Putting aside the more interesting later output that leaves us with the limpet trough agreed across all the models within 144hrs.

Then the upstream pattern shows differences between the GFS and ECM, not to flog a dead horse and for fear of sounding like a broken record but the more amplification upstream the better chance of a favourable outcome in terms of colder weather.

We are likely to see an interaction between low pressure heading east out of the USA and low pressure heading se out of Canada, these phase together and its the amplification of this troughing that can help deliver a stronger ridge ahead exerting pressure on the limpet trough to disrupt.

The GFS in the higher resolution has much better amplification of that troughing upstream although it continues its obsession with the limpet troughing for too long, the ECM has a more perilous way forward for cold lovers.

All in all we are reaching the timeframe where the disruption to that troughing will become better modelled, by the end of the weekend we should know whether its another false dawn or a pattern change.