Model Output Discussion 26/10 2012 >

[tinybill]

http://www.meteociel.fr/modeles/gefs_cartes.php?code=16&ech=192&carte=&mode=0

morning all pouring down here in suffolk , looking deep in to fantasy world its looking cold in the second week at the moment

[phil nw.]

The main difference between the gfs and ecm 00z ens mean this morning is how they handle the atlantic ridge towards T+240 hours, the gfs shows a flat ridge which barely has any effect for most areas whereas the ecm builds a stronger looking ridge that seems likely to push into the uk, both models agree on eventually pushing the trough to the northeast allowing arctic air to flood south with showers turning wintry and increasing the frost risk but for the next week, it looks like becoming very unsettled and cyclonic with lots of wet and windy weather seperated by brighter, showery weather and cold enough for snow on northern hills and mountains, temps generally below average but a bit milder in the southeast for a time, colder air arriving towards next weekend into the start of the following week. The gfs ens mean yesterday was much more favoured towards the azores/atlantic high having a major influence in FI, but today it favours a chilly unsettled outlook with winds mainly from north of west.

A good summary Frosty.

Good agreement for a week to 10 days of this unsettled spell over the UK.

With the trough modelled over the Uk for the coming week it means the coldest air from the Arctic is sent to our west into mid-atlantic.We can see what i mean here at T96hrs for example

the higher pressure too far west- ridging towards the Candian maritmes and the troughing setting up over or just to the west of the UK This is sometimes referred to as a west based -NAO.

Although this isn`t the best example, given the weaker heights modelled over the pole going forward, it gives an idea of how easy it is for the UK to miss out on the coldest flow when the pattern doesn`t sit quite right.

Having said all that temperatures for the UK will still be on the cold side of normal though as we will have a lot polar air in this cyclonic setup and with height the rain will likely fall as snow at times in the north.

There is just a hint appearing in the 00z mean ht.anomolies that by day 10 the pattern may start to move east somewhat.

moving the low heights towards Scandinavia which will open the gates to somewhat colder air coming towards the UK.

The 006Z GFS run moving the Azores high across in later frames seems on it`s own when viewed against the 00z outputs but we will know more on this when viewing the 12z`s later.

Edited October 28, 2012 by phil n.warks.

[TonyH]

A look at the week ahead comparing west Wales weather to the Midland's:

http://forum.netweather.tv/blog/309/entry-4494-weather-guide-monday-29th-october-to-sunday-4th-november-comparing-west-wales-with-the-midlands/

[MP-R]

I think there's a lot to be happy about in the models. The first week of November is looking quite similar in a way to the first week of November 2009. That week was particularly unsettled and stormy and featured many days of sunshine and torrential downpours often with hail, thunder and lightning in Bristol. The GFS is certainly looking more promising than this time last year when it was anomously warm.

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2012102812/gfsnh-0-168.png?12

Whilst the UKMO is awsome tonight - if things go towards the GFS these are the heavy snow situations to occur over the North of the UK ( pref at slight elevation)

where the atlantic hits the boundry of the polar front.

definate snow from that-

S

[lorenzo]

UK vanishes on the GEM run.. deepens the low.

[Summer Sun]

I know its FI but widespread snow by mid month

November 2010 repeated?

http://www.jp2webdes...o.uk/ds/gfs.htm

Edited October 28, 2012 by Summer Sun

[Cold Winter]

Unfortunately charts from T384 are completely useless when the position of this week's low pressure changes with every run! Impossible to say how things are going to pan out further down the line at this stage.

At the moment it looks like a wet and windy period for the UK with areas of rain and strong winds passing down from the northwest from late Tuesday onwards. The low pressure hangs around for a long time with further periods of unsettled weather moving across the country before the system eventually clears to the northeast next weekend.

[Liam J]

http://modeles.meteo...nh-0-168.png?12

Whilst the UKMO is awsome tonight - if things go towards the GFS these are the heavy snow situations to occur over the North of the UK ( pref at slight elevation)

where the atlantic hits the boundry of the polar front.

definate snow from that-

S

I know you live for the cold & snowy winter weather, Steve - Looking a bit closer into the chart, I'm sure even you couldn't make it snow from that. Specific details at this range irrelevant though.

[Zakos]

yes, I think the potential is definitely there for a repeat of November 2010.

GFS + ECM both going for a weak polar vortex and northern blocking. The details vary but the big picture remains the same.

jet stream pattern looks startlingly similar to December 2010 on the latest GFS

Take a look at the latest CFS forecast

whereas only a few days ago the CFS forecast this for November

In my opinion, the models have picked up on the potential of a cold and blocked November. You can say its just FI etc... but cast your minds back to last year, there was barely ever any forecast for a cold pattern to emerge, even at 300hrs+ (in Nov/Dec)

I dont remember how well the CFS performed last winter, but November is only a few days away, and for the CFS to suddenly flip from a flat zonal pattern to a cold and blocked pattern is encouraging for me.

I think there is the potential for a cold and potentially snowy weather pattern to emerge come mid November, with the cold predominantly coming from the North-East. Certainly very little sign of a formidable attack from the Atlantic, and also very little sign for the formation of a strong polar vortex.

Edited October 28, 2012 by Zakos

[UV-RAY]

Unfortunately charts from T384 are completely useless when the position of this week's low pressure changes with every run! Impossible to say how things are going to pan out further down the line at this stage.

At the moment it looks like a wet and windy period for the UK with areas of rain and strong winds passing down from the northwest from late Tuesday onwards. The low pressure hangs around for a long time with further periods of unsettled weather moving across the country before the system eventually clears to the northeast next weekend.

But it's a model discussion thread, so open to discussion as this is where trends are spotted.

[AWD]

Two things to note about the GFS Ensembles are;

there are a number of members going for two depressions below 990mb, one on the 1st & again on the 3rd. The one on the 1st is pretty much nailed now, with support from the Operational & Control runs, the one on the 3rd us more scattered, but with a notable amount of members going for a drop in pressure again. The Operational and control as of yet, don't support such a drop as much.

The other thing is that the Operational became a pressure outlier in he beginning of FI, which suggests to me that the HP could stay further west in the Mid Atlantic, therefore possibly bringing colder air further into November. Off course though, at this range it is pure speculation.

http://www.meteociel.fr/cartes_obs/gens_display.php?x=306&y=141&run=12&ville=Londres&runpara=0&type=1&ext=1

The GEM has a very deep depression to the north of the UK next weekend briniging a widespread wet & very windy spell of weather to all.

http://www.meteociel.fr/modeles/geme_cartes.php?&ech=144&mode=0&carte=0

http://www.meteociel.fr/modeles/geme_cartes.php?ech=144&code=0&mode=0&carte=1&archive=0

Some very interesting weather possible in the next week or so. Lots of rain & wind as pressure drops to possibly quite low readings, with convective showers rattling around the country in a cool rPm flow. Very autumnal charts.

[SMU]

I know you live for the cold & snowy winter weather, Steve - Looking a bit closer into the chart, I'm sure even you couldn't make it snow from that. Specific details at this range irrelevant though.

Your dewpoint chart shows Snow over the north- More specific the higher areas of west yourshire etc-

Widespread dewpoints in the south 3-5c however get into that region & they plummet to around 0/1c-

Post up the surface temp for that time now add some elevation........

Edited October 28, 2012 by Steve Murr

[andymusic]

Unfortunately charts from T384 are completely useless when the position of this week's low pressure changes with every run! Impossible to say how things are going to pan out further down the line at this stage.

At the moment it looks like a wet and windy period for the UK with areas of rain and strong winds passing down from the northwest from late Tuesday onwards. The low pressure hangs around for a long time with further periods of unsettled weather moving across the country before the system eventually clears to the northeast next weekend.

Not quite - as we know and because GFS runs as it does - it does have a habit of picking up these "trends" early - and this weekends snow appeared on the GFS model 1st also - generally though, blocking does seem to be a feature across all models at the moment and it won't take much for the cold and snow to attack the UK in the coming weeks!

[A Winter's Tale]

Good evening. Mostly cloudy and damp conditions should continue through the rest of this evening and overnight with the most of the precipitation in southern areas. However through the night the scattered light rainfall should be moving further south and clearer spells will develop over night across Scotland. Minimum temperatures of 4 to 10C. Monday morning should see some pleasant early sunshine across Scotland and northern Ireland - some cloud cover and rainfall however for the outer hebrides and northern isles - cloudier skies across southern Ireland, Wales and England but across western and northern parts there should be a few clear breaks. Some rain still lingering along the coastline of the channel and showers across some inland parts of Wales and central England. Through the afternoon and evening the clear skies should develop across southern Ireland, Wales and more widespread across some northern and central parts of England but still cloudier in the very south, the east coast of England too. Clear skies in southern and central Scotland as cloud cover and rainfall in the north west highlands with some hill snow makes it's way further south. Maximum temperatures of 4 to 12C. Monday night should be mostly dry other than a little precipitation close to the south coast of England and some showers around the seas and coastlines of the north. A mostly cloudy night - particulary in Scotland - but some clear breaks likely in the south. Minimum temperatures of 2 to 9C.

Tuesday should be an overcast day across the British Isles and rainfall in the north west of Scotland. Maximum temperatures of 7 to 11C. That rainfall affecting the north west of Scotland should spread further south during Tuesday night with Ireland, Wales, North west England and much of Scotland having a wet night with some particulary heavy rain in western Scotland. Minimum temperatures of 4 to 9C.

The unsettled theme continues into Wednesday, a mostly cloudy day other than odd sunny break in northern Scotland. Showers and light precipitation swarming the seas around Ireland and Scotland, persistent and heavy rainfall for the regions of the UK and Ireland surrounding the Irish sea and thin band of light rain along southern areas of England. Maximum temperatures of 8 to 12C. Wednesday night isn't much better I'm afraid with persistent, widespread and quite heavy rainfall across much of England but the rainfall in Wales and the south west would probably be lighter - the heaviest of the rain up and down the spine of England. A mostly dry night for Ireland and Scotland with little clear skies but there'll be showers around the coasts. Minimum temperatures of 3 to 11C.

Thursday however at the moment should be an improvement, the band of heavy rainfall should now be out in the north sea, a much drier day for inland parts of England and mostly dry day for Scotland too. An overcast day for southern England and Wales in particular but a few clear breaks could develop across northern areas. Further showers should affect coastal parts of the western Scotland and islands, western areas of Ireland and some rain near the channel coast. Maximum temperatures of 7 to 11C. Skies should be on the cloudy side for most during Thursday night but some clear spells possible in some southern areas. Also some clear breaks possible across norther Scotland but there should be some showers across Scotland but most of the showers should be in the sea out to the west affecting the islands and coastal parts of northern Ireland and showers should be possible across north western parts of England too and the risk of some light rain showers along souther coasts. Quite a cool night too with lows of 2 to 8C.

Certainly an interesting few days of weather, generally unsettled with plenty of showers at times aswell as some heavy persistent rainfall from fronts on some days. Generally cloudy for most with breaks in the cloud cover possible when it's not raining but Monday should be the best bet for sunshine during the next 5 days. Although it's unsettled with restricted sunshine, it's still an interesting period of changeable weather and fairly typical for this time of year. Temperatures on the low side and some cold temperatures on a few nights in places but conditions probably not too favourable for a frost. We know that next week, a depression will set up to the north west of the British Isles and winds could be quite strong at times - particulary Wednesday and possibly some windy conditions on Friday judging by recent charts for that date. So the weather associated with this particular low will be worth following during next week as it's a changeable scenario but at the moment there's plenty of debate on what could happen after the the end of the week in what is currently an interesting outlook that needs following - should make enjoyable model watching in what has been a fascinating autumn and the outlook for this coming week and beyond is looking interesting, changeable and typically autumnal.

[Liam J]

Your dewpoint chart shows Snow over the north- More specific the higher areas of west yourshire etc-

Widespread dewpoints in the south 3-5c however get into that region & they plummet to around 0/1c-

Post up the surface temp for that time now add some elevation........

I'd say cold rain or sleet at best on the very highest ground?

Edited October 28, 2012 by Liam J

[SMU]

• http://www.meteociel.fr/modeles/ecmwf/runs/2012102812/ECH1-96.GIF?28-0
  

Maybe some wintry ness to the showers in the NW- even in NI with -4C air...

Great start to the ECM

S

[January Snowstorm]

I'd say cold rain or sleet at best on the very highest ground?

Would be inclined to agree Liam, cold rain for most I would think.

Potential is there though!

[SMU]

I'd say cold rain or sleet at best on the very highest ground?

]

With Evap cooling pulling the ZDL level down- probably snow line lower than you would think-

Just remember the DP can be + 0C- I saw a few flakes Sat with the + DP +3c.

Anyway its all a bit of obsevational fun- but the threat remains-

120 ECM

http://www.meteociel...H1-120.GIF?28-0

Stormy for the south- COLD in the middle...

Remember the model wont show snow for that gridpoint if the parameters are not good for the location or city its linked to-

higher elevations away from cities will be colder & have a higher chance of snow- on that chart - almost a certainty for places like shap fell, Westmoreland etc to be covered with snow-

S

Edited October 28, 2012 by Steve Murr

[Methuselah]

I'd say cold rain or sleet at best on the very highest ground?

I'd think that it's just about possible, given torrential precipitation and a dead calm??

[SMU]

ECM more orientated to the GFS at 168...

S

[Liam J]

I'd think that it's just about possible, given torrential precipitation and a dead calm??

We could speculate all we liked but at this range and taking those charts at face value then I'd bet heavily against the liklehood of snowfall occurring at all. Anyway - we have a lot of ground to cover in the mean time

[Frosty.]

we have a lot of ground to cover in the mean time

In snow hopefully

The next few days look a little milder than recently with temps close to 11-12c but cooler in the north and not such an unsettled start ro the week, more like scattered showers on mon/tues but from midweek it looks like becoming wet and windy as low pressure winds itself up over the uk, eventually turning cold enough for wintry precipitation in the northwest by friday, a mix of rain, hail, sleet and wet snow as the air becomes more polar more generally by the weekend as the trough pushes further to the east . I think some very wintry charts could evolve through november.

Edited October 28, 2012 by Frosty039

[swfc]

quite a big move from ecm towards gfs this evening?bit suprised how quickly the blocking has diminished!!!!

[Cheshire Freeze]

quite a big move from ecm towards gfs this evening?bit suprised how quickly the blocking has diminished!!!!

Yep, looking at the 240 hr NH chart for the ECM12z, the vortex looks to be tightening- probably in response to the cooling strat. For me, a zonal few weeks is looking the form horse as we progress through November as I intimated in the winter thread last week.