Model Output Discussion 26/10 2012 >

[SMU]

Evening All-

All in all a pretty good ECM12z- After focussing on this cold spell for so long I would like to punt up 2 things to view for the next 10 days-

However before that-

Here was the 228 chart I saved ages ago-

& the best match ( ACTUAL )

A very very good performance from the 12z GFS-

First thing to keep an eye- A zipping shortwave that *COULD* depending on the allignment of the upper low bring some wintry weather across the midlands / high ground as it swings around the trough base-

http://www.meteociel...M1-144.GIF?27-0 note the shortwave swinging from west to east-

We will need colder upper air if we are to see any snow-

& finally the FIRST test of our pattern coming up- a surge in the mean zonal wind will try & dislodge the quasi stationary high in the atlantic-

Theres 2 things to think about with this-

* If as depicted by the GFS the energy gets through the block & the heights fall towards southern greenland then how long do we wait for the next blocking episode-

* ECM has turned up the focus on that period of time tonight as it develops a split over the south west of greenland- I have referred to this area many times so far this autumn & the ECM sees a shortwave pushing up the west @ day 10 teleconnecting to a northerly flow over the UK

OF NOTE IS THE GEM 00z & JMA 12z

http://www.wetterzentrale.de/pics/Rjma1921.gif

Easterly progression of the day 8/9 shortwave = average / cool conditions over the UK

Northerly progression of the day 8/9 shortwave = Cool / Cold conditions with Wintry showers in the North & frost else where-

The 2 solutions see an average or cold start to Nov- no much focus on mild air yet- although there have been some flirtations of the euro pressure belt moving North from its southerly locale- so far they have been few & far between in the runs & no making much progression into reality as the models continue to under estimate the higher than normal polar heights......

S

Edited October 27, 2012 by Steve Murr

[SnowObsessor90]

Edit: Nevermind

Edited October 27, 2012 by Anonymous21

[Chess01]

So how do things look for the middle of november are we keeping the block. Sorry for the lack of knowledge

[SMU]

Middle of November- to far to think about at the moment....

S

[Frosty.]

It might be premature to say this but there is some agreement for another Northerly toppler in about a week's time, the gfs 12z op run gets there a bit quicker than the ecm 12z but then the ecm does get there eventually, it looks a bit more potent on the gfs but again, mainly for the north as it takes a fair while to reach the south and by that time the whole thing is toppling as a ridge pushes into the cold air with a brief frosty spell, then the pattern begins to change with high pressure becoming centred to the southwest of the uk with the weather becoming milder and mostly dry in the south but remaining more unsettled and cooler in the north, the late FI gfs synoptics suggest the jet will be heading much further north with a spell of mildish settled weather for at least the southern half of the uk eventually. In the week ahead it looks like a fairly quiet start but a deepening trough slipping south to the western side of the uk and becoming a very complex feature, briefly milder in southeast britain midweek then a bit colder and with spells of heavy rain and strong cyclonic variable winds alternating with blustery showers and as the trough edges snail like further east, colder air spreads down the western flank of the trough turning the showers more wintry towards the north by next weekend, beyond next weekend the pattern looks as though it could possibly flatten out with more typical autumn fayre compared to our brief flirting with wintry weather.

[legritter]

Plenty of eye catching synoptics tonight on all modells , bearing in mind that in the type of weather currently being forecast for about 120HRS from now many other features will pop up .certainly not boring . with the possibility of some very interesting weather say next weekend . still convinced low pressure will finish up further south and east than currently modelled . this high to the far north very far north could set up shop ,but very big Iffs at the moment .just very quickly todays air mass was a joy to see and i took a look up there instead of sitting on computer , contrails only lasted all of 8 seconds , just about modell related ,upper air charts will tell you why ,change tomorrow ,

[Adam lufc]

Are contrails dictative of upper air. That's interesting???.....

[Frosty.]

Just to add, although the Ecm 12z takes longer to bring in the Northerly, the set up looks more solid with more scope for longevity compared to the gfs 12z n'ly toppler, the only advantage of the gfs arctic blast is it's not so FI, the ecm looks better but at this range is rather less likely but the overall evolution looks realistic if the trough can be shunted further east, not too far though or the pattern will soon flatten out with the azores/atlantic high eventually becoming a major player sadly (from a coldies point of view).

[legritter]

Are contrails dictative of upper air. That's interesting???.....

whilst waiting for GFS to update thought id just answer Adam Iufc,Short lived contrails ,hardly any water vapour available in that given part of the atmosphere ,so ice particles that are formed very quickly return to vapour ,if you type in Contrail science on GOOGLE then follow onto different sites ,so along with modell watching we can all become contrail buffs ,cheers gang ,

[damianslaw]

Its an unsettled outlook for the foreseeable future, with the upper trough once again set to park itself directly over the country meaning slow moving bands of rain especially in western parts with snow on higher ground. Temperatures will stay at or below average for the foreseeable future as well, with most of the country locked in sub 548 dam air, with 528 dam air possibly returning to northern parts later next week bringing increased risk of wintry precipitation to lower levels - all will depend on the position of the trough - if it moves east then another northerly could easily be on the cards next weekend.

The synoptical pattern at present is not the usual west-east atlantic flow, the jet continues to take a more southerly position, a very different set up to this time last year. This year has been punctuated by long spells of very similiar weather with the trough stuck in the same position for exceptionally long periods... often over the country, indeed its been remarkable in how long it has now had a love in with this country - preety much since April with only occasional breaks.. could we be in for a very wet cyclonic cold November with significant snowfall always a major threat as we sit on the polar side of the polar front? Its a long time since we have seen such a November - probably have to go back to 1996. (Nov 2010 was not a cold wet cyclonic month).

[Cloud 10]

The NAEFS remains consistent in moving the main troughing just to our East in the

10 dayish range with corresponding ridging around Southern Greenland.

Also a strong signal for below average temperatures at the same time.

Looking at the model output in general terms for the next couple of weeks,i would say

less cold but more unsettled for week one then turning less unsettled but colder

during week two.

[Neilsouth]

I did ask this before but got ignored or nobody noticed..

Where does the trough usually sit itself in a zonal winter or shall i say typical 90's winter

[SMU]

iceland -

accompanied by higher pressure to the azores

S

[Cloud 10]

I did ask this before but got ignored or nobody noticed..

Where does the trough usually sit itself in a zonal winter or shall i say typical 90's winter

This chart from October 1998 looks fairly zonal with the main trough to our North-West

near Iceland giving a strongly positive NAO.

Compare that with what we have now with the main trough to our East/North East

and high pressure over the Mid-Atlantic and Southern Greenland giving a

negative NAO.

[Neilsouth]

Thankyou

[IDO]

Very disappointing GFS 0z run this morning. A 16 day run of cool, initially wet LP/trough dominated, edging to HP (from T240).

Very wet for some (S & W facing coasts):

http://www.weatherwe...uktotpcp192.gif

The PV is releasing cold but that energy goes to a different axis:

http://cdn.nwstatic....384/npsh500.png

Uppers remain cool, especially T850's throughout the run, but only around 0c, and even to our east they lose the -5's.

The trough that develops in FI in the US, where the action is, disrupts the jet downstream and the Atlantic jet breaks up for the last five days of the run:

http://cdn.nwstatic..../348/hgt300.png

So blocking and little zonality is the order of the day on this OP run, however blocking not favouring our neck of the woods at the moment.

The OP run lies in the cooler options late in FI (ENS mean and control milder):

http://cdn.nwstatic..../t850London.png

However good agreement on the next ten days; cool and wet, snow risk nominal: yuck.

Edited October 28, 2012 by i'm dreaming of...

[Frosty.]

Very disappointing GFS 0z run this morning.

Since everyone has their own preferences, i'm sure plenty of people will find something to like about the 00z op run, but I don't ever put much stock into what an individual op run shows, the ens mean is the best guide. Anyway, cool and unsettled within the reliable although early in the week relatively calmer before low pressure takes full control.

[wolvesfan]

Morning all,

Although the cool pattern hasn't benefitted us too greatly,the overall big picture is full of potential for a cold spell to develop (unlike last autumn).All the telleconnections are favourable and the strats our friend at the moment.the main mods might be showing standard autumn fayre for the uk but looking at the northern hemisphere pattern things wouldn't have to alter much for us to recieve some significant cold.uk met seems to be indicative of this on this mornings run,

[Gibby]

Good morning and welcome to GMT. Here is the morning look at the 00zs from GFS, UKMO amd ECM.

All models are agreed on the evolution pattern through this entire week with only small differences between the synopses between them making little difference to the weather experienced down here on the surface. Today has seen cloud and occasional rain move down from the NW overnight moving over cold air and making for a raw and cloudy day with mostly light rain at times for all. Later in the day a cold front will sink slowly South with a band of more organised rain, behind which skies will clear in the North later tonight. Further South some heavy rain will start the working week off before here too things brighten later with some sunny spells and just scattered showers in the North and West. A patchy frost is likely tomorrow night with Tuesday probably being the best day of the week as something of a ridge passes through the UK with a freshening West or SW breeze picking up later and turning the weather more cloudy and windy in the NW by the end of the day as a deepening Low sinks down close to Northern Scotland. By Wednesday this Low has become very deep and it dominates the UK weather for the rest of the week and weekend as it becomes complex centred near Northern Scotland before moving slowly East and filling at the weekend. The Westerly flow around it will cover all of the UK with troughs embedded bringing spells of rain and strong winds mixed with more broken cloud and showers, when the air is cold enough for rain to fall as snow on Northern hills and mountains.

GFS then moves into the second week with a slow improvement creeping in from the West in the shape of a ridge of high pressure as the Low pressure finally moves away East. It takes until the middle of the week for any noticeable changes at the surface with the early and middle days still cold and showery with further snow on Northern hills in a cold NNW flow. By the end of the week High pressure has moved in from the West but the air will be cold and frost and fog will become a large player in conditions towards the end of the run as the High holds on. A cold SE flow develops at the end of FI in the far SW otherwise cold and foggy seems the most likely weather at the end of the run.

The GFS Ensembles show a rather cold couple of weeks in store as a cold zonal pattern seems likely to dominate. Bouts of precipitation is spread about over the run in all areas. 850's are close to the 0C level when taken as an average which means a couple of degrees below average temperatures can be experienced at the surface and cold enough for some snow at times on Northern elevations abve a couple of thousand feet.

The Jet Stream shows the Northern arm sinking South over the Atlantic and UK to set up residence South of the UK in a week's time.

UKMO for midnight on Saturday shows Low pressure centred to the North of Scotland with a rather cold and showery NW flow over Britain. Some heavy showers would be likely, especially in the North and West with hail and thunder possible, as well as sleet or snow on Northern hills.

ECM shows even deeper Low pressure early next weekend with it only moving very slowly away East with a cold and showery NW or North airflow maintained over the UK in it's wake. The showers would continue to be widespread at times and heavy with sleet or snow over hills in the North.

In Summary once arrived the Low pressure later this week is set to dominate the weather over the British Isles for some considerable time. There is a trend shown between bot GFS and ECM this morning to begin to rise pressure in from the West from about 10 days time although this is tentative an slow and should it evolve a cold and frosty spell looks like it could develop in FI but more support is needed in subsequent runs to take this verification seriously this far out. So in a nutshell all areas can expect a week to 10 days or so of very unsettled and windy weather from midweek with showers or longer spells of rain with sleet and snow at times on Northern high ground as temperatures remain somewhat below the seasonal norm.

[chionomaniac]

The GFS has the following low predicted to head NE as shown -

I am just not convinced by this.....

24 hours on and one can see that this trough is now less inclined to head NE. Now holding its own in a long wave trough. Still some way out though and things can change in either direction, but my initial reason for posting this is that I saw the possibility that this trough could become cut off - and that possiblity has certainly not diminished today.

[Cloud 10]

24 hours on and one can see that this trough is now less inclined to head NE. Now holding its own in a long wave trough. Still some way out though and things can change in either direction, but my initial reason for posting this is that I saw the possibility that this trough could become cut off - and that possiblity has certainly not diminished today.

"strat bluffer" a new user name perhaps.

Fascinating watching how the models are dealing with the low pressure for the end

of the week,with potential for severe gales somewhere.

A few options from the 00z runs.

http://modeles.meteo...gfs-0-120.png?0

http://www.meteociel...1-144.GIF?28-12

http://www.meteociel...20-21.GIF?28-06

http://modeles.meteo...em-0-126.png?00

[Severe Siberian icy blast]

Well I'm very surprised to see how quiet it is in this place after looking at the ECM , it looks very wintery for the time of year with the uk sat in cold uppers (-2,-3's) for the most of the time , but then a northerly block setting up nicely toward the end of the run, it's the best of the lot really this morning which looks full of potential and surprises especially if we get a short wave during night time . Interesting times.

[SMU]

Evening All-

All in all a pretty good ECM12z- After focussing on this cold spell for so long I would like to punt up 2 things to view for the next 10 days-

However before that-

First thing to keep an eye- A zipping shortwave that *COULD* depending on the allignment of the upper low bring some wintry weather across the midlands / high ground as it swings around the trough base-

http://www.meteociel...M1-144.GIF?27-0 note the shortwave swinging from west to east-

We will need colder upper air if we are to see any snow-

& finally the FIRST test of our pattern coming up- a surge in the mean zonal wind will try & dislodge the quasi stationary high in the atlantic-

Theres 2 things to think about with this-

* If as depicted by the GFS the energy gets through the block & the heights fall towards southern greenland then how long do we wait for the next blocking episode-

* ECM has turned up the focus on that period of time tonight as it develops a split over the south west of greenland- I have referred to this area many times so far this autumn & the ECM sees a shortwave pushing up the west @ day 10 teleconnecting to a northerly flow over the UK

OF NOTE IS THE GEM 00z & JMA 12z

http://www.wetterzen...cs/Rjma1921.gif

Easterly progression of the day 8/9 shortwave = average / cool conditions over the UK

Northerly progression of the day 8/9 shortwave = Cool / Cold conditions with Wintry showers in the North & frost else where-

The 2 solutions see an average or cold start to Nov- no much focus on mild air yet- although there have been some flirtations of the euro pressure belt moving North from its southerly locale- so far they have been few & far between in the runs & no making much progression into reality as the models continue to under estimate the higher than normal polar heights......

S

Morning All-

A surprising amount of negativity here this morning- Although against my last run of forecasting im not happy with the GFS & prefer the euros, strange eh!?

The ECM has again caught my eye this morning - both in relashon to the above outputs I commented on last night-

So our old favourite Greenland this morning we see even more of a negative tilted system push up the western side

http://www.meteociel...1-192.GIF?28-12

Now that remains in situ out to 240-

This run will continue with sustained flow from the North & NW post day 10-

Also an unexpected snow event ( localised ) for the Northern part of the UK at 132- you cannot actually see it on the model however as mentioned a shortwave zipper across the UK in sub -3c air will produce snow on the northern flank if the upper trough is alligned correctly-

( maybe someone can punt up the weatherunderground PPN charts for then as I dont know the link)

Finally the UKMO 144 in the mix as well

http://www.meteociel...44-21.GIF?28-06

Again eyes towards western greenland looking at the split system off the western coast-

If you look to western greenland on pretty much any run & any low is splitting its highly likely a westerly flow will not force its way into the UK......

S

Edited October 28, 2012 by Steve Murr

[lorenzo]

UKMO 144 caught my eye this morning, all 3 ( UK/Euro/GFS) handling the orientation of our trough differently.

Potential link up of heights on the UKMO...?

ECM 12z run last night had similar effect from the ridge at later timescale, be interesting to see what it is showing on the 12z run tonight at around 192.

MJO analogs from the Cassou paper indicate that an NAO +ve phase ( almost heretical writing that here but nonetheless on the table) is preceeded by phase 3 and 4 of the MJO. Whilst the pattern seems not strong enough to impact fully in terms of the analogs, cannot be discounted, this is however a route back to blocking with phase 5 of MJO generally featuring a Scandi Block.

Again the dynamical forecasts have great difference, GFS keen on phase 1-2 and moving around in this area whilst the ECM has things heading to phase 4 by 10th November, With a lag of 10-12 days then with this teleconnection alone it would mean +ve NAO waning by the final third of November. That's the read but closer to it's origin the MJO does not deliver a good lead and need to look elsewhere to attempt to map out November.

Edit to add MJO Charts.

Edited October 28, 2012 by lorenzo

[Frosty.]

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.