Model Output Discussion 1st Nov.2013

[Cloud 10]

i guess thats the easy part crewe - then we have to get the cold here !

 

Quite a few examples of that amongst them. 

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-2-1-372.png?12

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-11-1-324.png?12

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-18-1-336.png?12

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-20-1-360.png?12

[Barry12]

ECM looks chilly

 

Edited November 7, 2013 by Barry95

[Polar Maritime]

That last chart is a corker posted by Cloud 10. A full on cross pole Northerly.

[Snowman.]

 

Almost cross polar here.

[Snowmadsam]

ECM is still carrying on its trend to cool down around 15th-17th of the month....

[forecaster]

50% of the members represented by the mid-Atlantic ridge outcome in the GEFS:

 

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cslp&HH=348&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

[Panayiotis]

The 12z GFS ensemble has been the best this autumn for snow chances in my location!

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=202&ext=1&y=139&run=12&runpara=0

 

The ECM, especially the latter half is something quite interesting too! 

Edited November 7, 2013 by Panayiotis

[joggs]

Sorry but what would influence would an -AO have on our winter in the UK ... What is a -AO ?

Its a negative arctic oscilation and generally promotes arctic highs meaning the vortex been weaker/moved about and a better chance of cold flooding to mid lattitudes i think lol.In the last 6 years or so this seems to have become more prevalent and tanked(gone really neg),this coupled with a neg nao(north atlantic oscilation)really increases our chances of cold but not a certainty!.We need alot of things to fall into place for prolonged,severe cold.Hope that helps.More experienced members will explain better lol. Edited November 7, 2013 by joggs

[Tim Bland]

The 12z GFS ensemble has been the best this autumn for snow chances in my location!http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=202&ext=1&y=139&run=12&runpara=0The ECM, especially the latter half is something quite interesting too!

Nice to see the GFS is a mild outlier at the end! Somewhat peeing on Gavin's fireworks

[johnholmes]

some musings from an old met man on the 500mb anomaly charts as they are at the moment and what MIGHT happen?

 

Changes in the 500mb noaa charts - looking 6 nov 13.pdf

 

[joggs]

some musings from an old met man on the 500mb anomaly charts as they are at the moment and what MIGHT happen?Appreciated John,thanks.Changes in the 500mb noaa charts - looking 6 nov 13.pdf

some musings from an old met man on the 500mb anomaly charts as they are at the moment and what MIGHT happen.Changes in the 500mb noaa charts - looking 6 nov 13.pdf

Appreciate it John,thanks.

[bobbydog]

On that basis everything is a realistic possibly as long as there is a chart for it.

 

For example the latest 384hr is just as much a 'realistic possibility', but that is only heading in one direction by T+408hrs!

 

 

As BA has suggested there may well be a route to something colder developing for the last 3rd of Nov, but posting charts at 384hr

or even 240hrs and calling them 'a realistic possibility' is still complete folly imo.  You normally only need to wait 6hrs and the

previously 'interesting' chart become anything but.....and visa versa of course. 

 

i'm fully aware of the implications of "FI", anything at that range is a realistic possibility. there could be 100 realistic possibilities. my point is, they could happen. they are not impossible and bearing in mind, FI is regularly showing a very big aleutian high along with atlantic HP ridging into greenland, it is more of a "realistic possibility" than usual

[Summer Sun]

Latest from Gibby, something for everyone unless it's severe frosts, fog and snow your after.

 

All models show a Westerly flow across the UK with showers in Northern and Western areas with the overhang of cloud related to the front close to the SE moving away soon so that these areas too join in with the showers and clear or sunny intervals tomorrow. It will feel chilly especially over the North and a touch of frost is possible overnight in the East. On Saturday another trough moving East may bring a further spell of showery weather before clearing skies under a ridge gives a cold and possibly frosty night on Saturday night. By Sunday a warm front along with a freshening and mild SW wind takes over with rain spreading NE over all areas later in the day. Through the early days of next week a series of weakening fronts crossing East and SE across Britain brings alternating periods of mild then cooler weather with short periods of rain and strong winds at the transition points. 

 

GFS then maintains this pattern throughout the remainder of the run with temperatures alternating slightly either side of average without ever becoming desperately mild or cold. The heaviest of the rain and the strongest winds will nearly always be over the North while Southern Britain could see some drier and lengthier brighter spells at times. 

 

UKMO tonight closes it's run with Low pressure to the North and High pressure to the South with a strong Westerly flow over Britain, strongest in the North where gale or severe gale force winds are possible. Rain would be sweeping East across the UK through the day. 

 

GEM shows a very windy spell with strong to gale NW winds as Low pressure moves SE over Europe. High pressure to the SW will ensure the driest weather would be found in the South while NE areas in particular would see some showers, wintry over hills for a time before mild and changeable conditions return from off the Atlantic at the end of the run. 

 

NAVGEM shows a chilly spell later next week as Low pressure moves SE over the UK with strong, chilly and showery NW winds giving way to a temporary NE flow over Eastern England. It then looks set to turn drier and fine over the UK but cold with night frosts after the end of the run covering next weekend. 

 

ECM tonight looks much like this morning with fast changing weather patterns in a blustery and sometimes cool Westerly airflow. Some rain at times is expected for all, heaviest in the North in the strongest winds while the South sees lighter rain and longer less windy spells in between. The end of the run shows a chilly and showery NW flow over the UK with wintry showers over the North and East ahead of a ridge of High pressure. 

 

The GFS Ensembles tonight show an up and down pattern in temperature over the two weeks. The general rule of thumb will be for the contrasts to be less felt over the South close to High pressure to the South and SW while the North sees more marked chilly spells at times with strong winds and wintry showers. However, there is nothing alarmist shown in the output tonight with rainfall though frequent and present throughout the run looks likely to be non-disruptive.

 

The Jet Stream shows a strong ridging North over the Eastern Atlantic early next week before it shows signs of collapsing back SE over the UK before reliability falls away in it's output. 

 

In Summary the weather looks like being very changeable over the period with fast changing scenarios between mild and cloudy weather with some rain, especially in the North and West mixed with brighter and drier weather if colder with wintry showers and night time frosts more especially over the North and East. All in all it looks a typical Autumn pattern of weather over the next few weeks with something for everyone unless it's severe frosts, fog and snow your after.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[Polar Maritime]

or live in the South Gav...

[I remember Atlantic 252]

Latest from Gibby, something for everyone unless it's severe frosts, fog and snow your after.

 

 too early for that just yet, i'm not bothered yet

[Mr Frost]

Latest from Gibby, something for everyone unless it's severe frosts, fog and snow your after.

 

Let's keep the severe frosts and snow for Winter - it is only Autumn after all. :-D

December, January and February is when I will be after the above!

Can just imagine you building this Gavin when the first decent snowfall settles...

[gottolovethisweather]

Any chance we could get back to discussing the model output and leave the name calling for the school playgrounds. Even if I had a chuckle at one or two of tonight's posts they don't actually offer much MODEL OUTPUT DISCCUSSION and as I'm here to learn about what weather is on its way for the UK, I'd like to see some new content with plenty of substance.  

 

Thanks muchly.

 

gottolovethisweather

Edited November 7, 2013 by gottolovethisweather

[SnowBallz]

Sorry but what would influence would an -AO have on our winter in the UK ... What is a -AO ?

 

 Hi,

 

The AO (Arctic Oscillation) is one of the indices used to derive a measure of variation from what would be considered normal surface level pressure.  In general, a +ve reading is indicative of low pressure atop the pole, which invariably tightens the PV (Polar Vortex) and makes it less likely for that really cold arctic-sourced air to drop to the lower latitudes; it remains bottled-up in the higher northern regions instead.

 

Conversely, a -ve is indicative of higher pressure around the polar region.  Higher pressure would tend to suggest either a weakened or displaced PV, so less oscillation means that colder arctic air is more able to filter south and into abnormal latitudes.

 

It's one of a number of indices, and it's important to understand that there is no one which - in isolation - foresees cold weather; it's usually a combination, and - even then - a degree of factors all have to become conducive.

 

Hope that helps,

SB

[damianslaw]

Models continue to suggest a trend towards a northerly by the end of next week - still a long way off, but there are strong signals of mid atlantic heights building during next week with the formation of a scandi trough, hence, a northerly of sorts could be on the cards and given how cold it is currently over the north pole it could be a sharp potent affair for the north. GFS latched onto this synoptical evolution yesterday and ECM has followed suit today.  Lets see if they continue to show such a scenario in the coming days.

 

Also for the first time in a long time low pressure has dug into central europe eroding european heights which do look like at long last weakening.

 

I said yesterday the current outlook is very normal for the time of year - all very seasonal, a period definately more renowned for being atlantic dominated than anticyclonic.

 

When I think of November I think of rain, little sunshine, gales, darkness and general drabness sprinkled with the odd crisp bright or foggy spell especially during the first two thirds - a change to something colder often does surface by the 18th-20th though. I enjoyed November 2008 for being very seasonal, with increasingly colder weather towards the end of the month. November 2010 was very much a one off and the likes of Nov 2005 and 1993 and 1985 which all saw notable cold weather in the second half of the month are preety rare as well.

[Summer Sun]

GFS 12z showing more of the UK becoming less cold over the next 8 days Scotland remains the coldest place

 

 

Compared to 00z this morning

 

 

Certainly a less cold run from GFS this evening

Edited November 7, 2013 by Summer Sun

[legritter]

Generally speaking the modells at the moment are pointing to what the uk would expect at this time of year .although signs of high pressure probably becoming more dominant in the far charts at the end of runs .this can be a frustrating hobby ,with ups and downs but sometimes we all get what we crave for .if someone had said to me 30/40 yrs ago about future forums and charts and data looking ahead for 2 /3 weeks or sometimes longer i would have jumped for joy ,but in those days when the holy grail was just around the corner you were even more unaware than today .we have moved on a long way in meteorology and although finer detail is still hard to pin down we would know in plenty of time if a megga freeze was on its way .but its great to discuss our thoughts on a forum ,have a bit of fun now and again ,and all learn from each other .hope this isnt too far off topic ,many years ago i had contacts in Met office ,i would speak to my friend who worked there and on many occasions they would tell me ,high possibly building over scandy or iceland then within 24 hrs or so i would be told its all changed its now the azores high is a coming .so in all reality we have moved on but the time scale as changed ,so i would say you never know what will show up tomorrow its a massive atmosphere up there with so many Unknown possibilitys ,and after spending hours and hours looking at historical charts and data i still firmly believe that deep cold can set up Very quickly given the right atmospheric conditions as happened around 20th january 1947 .so yes its great having all this info PV /stratosphere ,jet stream charts etc etc but we must not lose the fun and the hunt for our desired weather type .

[Cloud 10]

ECM 12z ensemble mean between 168 hrs and 240 hrs shows the polar vortex being squeezed forcing arctic air to lower lattitudes,with troughing into eastern europe,so expect more northerly goodness to start showing up in the model output over the next few days.

 

168hrs..  240hrs..

[Panayiotis]

GFS 12z showing more of the UK becoming less cold over the next 8 days Scotland remains the coldest place

 

 

Compared to 00z this morning

 

 

Certainly a less cold run from GFS this evening

Yes but its after the 15th where the interest and potential is..

[Ali1977]

Different looking GFS tonight in FI, big greenie high coming

Edited November 7, 2013 by Ali1977

[chionomaniac]

The route to cold this November will always be from a northwesterly airflow around the back of an Atlantic ridge and at last this is starting tp possibly show up on the extended anomaly charts.

 

Here is the November expected anomaly composite based on the closest anologue years. 

 

Analog yrs Nov H500.png

 

The GFS 11-16 day anomaly charts are starting to have a similar look about them - so confidence for an Atlantic ridge can grow tentatively for later in the month.

 

12zgfsensCumulative500mbHeightAnomalyNH360.gif

 

THere is a bit of a confusing signal between the MJO and GWO, but the one thing that I can see omnipresent this winter is already showing. That is the strong Pacific ridge.

So, it was mentioned earlier in the month that the best chance of a cold outbreak would this month would be from around the back of an Atlantic High and I still think that this hold true.

 

Presently, the current pattern is dominated by a stonking Pacific Ridge aligned to a developing polar stratospheric vortex. This developing stratospheric vortex is yet to fully control the pattern - when the polar stratosphere is still cooling during the early winter, it is prone to strong tropospheric wave activity, however I think that it is unlikely that we will see the local wave breaking over Greenland that we saw in 2010, this year. I don't think that the Atlantic high will be strong enough this year to break the grip of the developing vortex. But that is not to say that we cannot develop a colder pattern during the second half of November, especially further north.

 

Stepping back and looking further afield we have had the AAM tendency drop and then rebound massively.

 

 

Lowering and negative AAM in the northern latitudes will have the effect of powering the northern ar of the jet stream and increasing the westerly airflow, so ideally we don't want this but want to see any positive AAM deflected poleward. If positive AAM surges around 60ºN then the net effect at this latitude will be an increase of easterly flow. Any easterly flow here will reinforce mid to high latitude blocking - but will the block be in a favourable position to  affect the UK. Well looking at the tendency graph above, currently the positive AAM looks too far south to affect our latitude favourably.

 

However, it is likely that the increase in AAM will nudge the GWO into a more favourable position - as suggested below - into phases 5>6>7.

 

 

Lorenzo, has brilliantly constructed some GWO H5 composite analogues for the phases of the GWO in November. These tend to suggest a reinforcing of the Atlantic block - but will it be far enough north?

 

 

When we look at the ECM and GFS cumulative anomaly charts then this Atlantic block gains credence.

 

 

and further afield

Tentatively, a suggestion here of a west based -ve NAO, 

 

There is very little indication that we will see a major wave breaking event leading to a tropospheric led Greenland block at this point. Back in 2010 when blocking in this area was indicated it was very well supported in the stratospheric models with severe splits in the vortex right up to 30 hPa.  There are no such indications that this is on the cards at this time (but we certainly can't rule it out this early in the season). 

 

Every year in the strat thread we learn a little bit more about the strat/ trop interactions and this year is no different. I have included a section in the first post that particularly covers how the troposphere can 'set up' a change in the stratosphere that then feeds back and reinforces a change in the tropopsheric pattern - perhaps Steve M missed this when commenting on the thread last night. However, and as ever, if the stratosphere cools to well below average by December then the subsequent strong vortex will influence the tropospheric pattern in the following weeks.  Yes, this is simplistic and there may be a chance of blocking before this occurs, but it is disingenious to suggest otherwise when winter is well set. At that point we will need (tropospheric led) strat feedback to break the cycle.

 

But still a little more to keep us interested in the next few weeks regarding cold potential than there has been in autumn so far.