Model Output Discussion October 2012

[OldMetMan]

Having watched the models dither a lot for a few days, I am really quite surprised today to see the GFS keep a reasonable consistency throughout today's runs, and what a weird outlook it portrays - 528dm thickness values across the whole country!?

I think what has been causing the confusion in the last day or two is the handling of Hurricane Raphael as it transitions into a post-tropical low and the models haven't seemed able to determine where it will go. But now I think there are begining to get a better handle on it, leaving us with its remains as a slow-moving LP out in the Atlantic.

Meanwhile, whilst the GFS is currently decisive in pulling in Arctic air in the medium to long-term, the ECM is somewhat similar but keeps LP much farther north, whilst the other models have HP near or to the east of the UK.

It is worth considering what is happening now. The 500mb is taking on a more decidedly blocked look with an upper high to our N, which has been there a few days, gradually retrogressing towards Greenland and is part of an Omega block in configuration:

As the current active LP systems end up merging over the UK, with the associated upper trough disrupting, it seems reasonable to accept that, as the LP over us weakens, it will merge with the Atlantic LP and draw in warm air for a few days. After that, the GFS development is quite plausible - I have seen this type of transition occur in the past - but of course it is still too far away to put too much trust in it. However, in several days time, if this theme persists, then there is a good chance of some unseasonably cold weather. Personally, I think it will, maybe not quite as drastically as the current GFS maintains, but this type of block occurring now would be most interesting, as would its significance towards what type of flow we can expect in the weeks to come, i.e. the tendency for 500mb patterns to recur. I shall have more to say over the next day or two to see if the hemispheric pattern appears to support the GFS outlook

This has been a year of many extremes, with some notable records broken. Maybe we shall see an "earliest snow" record under threat!

[legritter]

a very interesting modell discussion tonight Gang ,The words [ Preview of coming attractions ] comes to mind .IF NORTHERN BLOCKING DOES SET UP , and i am a bit of a cherry picker ,im sure this forum will go into meltdown .but charts tonight in the reliable shows plenty of rain on the way ,strong winds ,hvy showers , and even some warmth eventually in a few places . and the possibility of flooding issues yet again , well we have certainly had our Cake recently and who knows the Icing could be just around the corner . i must admit i did get excited over or just about a week ago when modells first hinted at the possibility of high pressure setting up shop to our north then it seemed to vanish , i must admit i had a sneeky feeling that modells would once again show this ,iv spent hours looking across northern hemisphere and arctic and things are looking good ,some good autumn signs ,it will be interesting watching met office 16/30 day updates ,regards

[Cloud 10]

CPC throwing some weight behind recent GFS output in today's update.

Climate Prediction Center - 6-10 and 8-14 Day Prognostic Discussions

Climate Prediction Center - 8-14 Day 500mb Outlook

[andymusic]

a very interesting modell discussion tonight Gang ,The words [ Preview of coming attractions ] comes to mind .IF NORTHERN BLOCKING DOES SET UP , and i am a bit of a cherry picker ,im sure this forum will go into meltdown .but charts tonight in the reliable shows plenty of rain on the way ,strong winds ,hvy showers , and even some warmth eventually in a few places . and the possibility of flooding issues yet again , well we have certainly had our Cake recently and who knows the Icing could be just around the corner . i must admit i did get excited over or just about a week ago when modells first hinted at the possibility of high pressure setting up shop to our north then it seemed to vanish , i must admit i had a sneeky feeling that modells would once again show this ,iv spent hours looking across northern hemisphere and arctic and things are looking good ,some good autumn signs ,it will be interesting watching met office 16/30 day updates ,regards

what he said!

[Geordiesnow]

Have you viewed the 12z GFS?

Yeah and any cold shot comes at 192 hours, come on Cloud 10, you should know by now from experience of these set ups, they are highly complicated, don't get sucked into the charts.

There does seem to be a trend from the models to drop colder air on the Atlantic side of the Arctic into Scandinavia which has been lacking so far and as I mentioned in previous posts, the Arctic to some extent will have height rises if albeit quite a west based NAO by the looks of things so you certainly can't rule out a cold shot like the GFS 12Z is showing.

All that said, for the foreseeable, the outlook from the weekend onwards is painted as one of getting drier and warmer on a more widespread scale, all the models seem to agree on that. Its just the detail that needs firming up on.

Edited October 16, 2012 by Geordiesnow

[damianslaw]

Models continue to show a southerly flow to end the week, but heights to the SE are shown to be weaker than yesterday and more importantly slightly further north which in turn will mean more of S/SE flow than a direct deeply drawn southerly. GFS continues to quickly build heights over Greenland into next week with low pressure developing over N Scandi - these two forces quickly kill the SE flow and we end up with a very chilly northeasterly/northerly flow with a very strong robust greenland high.

ECM less keen on developing strong heights over Greenland compared to GFS, but it still shows them, however, it wants to bring in a southerly tracking jet with associated low pressure - which would result in rather cold wet weather with snow on higher ground in the north.

The models appear to be reacting to the remains of ex hurricane ... don't know the name, its path will determine how the month end pans out, if it takes a more northerly path i.e. ECM route an unsettled chilly end will occur with low pressure sitting over the country, if it takes a more southerly path and stalls in situ, then GFS scenario would be very plausible - potentially one of the coldest ends to October in a long time..

The charts are certainly offering up very non-late October standard synoptics, we've been here before in late October 2008, 2009 when the atlantic was prevented from its usual west-east path, in 2008 we had the very cold northerly, and 2009 with high pressure to the east. Its far to early to speculate on the winter, but both following winters saw major disruption of the PV much more so in 2009, with a number of wintry episodes from the north and east..

[Cloud 10]

Yeah and any cold shot comes at 192 hours, come on Cloud 10, you should know by now from experience of these set ups, they are highly complicated, don't get sucked into the charts.

There does seem to be a trend from the models to drop colder air on the Atlantic side of the Arctic into Scandinavia which has been lacking so far and as I mentioned in previous posts, the Arctic to some extent will have height rises if albeit quite a west based NAO by the looks of things so you certainly can't rule out a cold shot like the GFS 12Z is showing.

All that said, for the foreseeable, the outlook from the weekend onwards is painted as one of getting drier and warmer on a more widespread scale, all the models seem to agree on that. Its just the detail that needs firming up on.

Not getting "sucked into" the charts,but comparing tonight's cpc 500mb outlook with the

gfs 12z anomaly chart does lend pretty good support for the gfs.

[snowfall09]

Couple of tweets from some 'weather experts'.... il let you judge their credibility

From Joe laminate floori, "Much of Europe to turn cold for November too. N Hemisphere in for a wild winter this year. Global warming will turn to climate change".

From Matt Hugo, "Interesting update from the EUROSIP seasonal model combining the UKMO ECMWF & MeteoFrance which supports a blocked/potentially colder winter"

[SMU]

Evening All-

I can actually tap up post from home now-

I can sort of answer the questions highlighted earlier-

* Why ignore the 06 + 18Z

* When I choose one model over another

* when is the GFS better than the ECM-

Some times I think people why im ignoring runs & when I selecting partlicular runs to go with, when to ignore the ensembles etc-

Well, I place a lot of what ive seen from the models V what actually happened, Within this particular runs have different failings & models do well at some things V the other-

For example what model would I pick tonight- 12 Z GFS hands down- I must be clear- its not always the coldest model, its the model & the run that feels the most seemless in transition & generally feels the best 'authentic' representation of what happens in real life.

Again I give a lot of weighting to what ive seen before-

The ECM comes out top, so from that you can NEVER discard a run, especially the 12z, however even this model has its poor moments ( take today for instance ) on these occasions I will take the ECM at face value but put heavy weighting to the GFS, with sometimes a blend of the 2.

FWIW the ECM is very strong in Easterlies, with the GFS far to progressive, the GFS does well in Northerlies & greeland high scenarios, cross polar flow situations ( like now ) with strong developing aleution Highs there is often massive variability at 168-240 range so you may go 4-6 runs before seeing the right outcome-

I recall this happening last year with the aleution high.

Perhaps we should put my theory to the test JUST based on the feel of the outlook....

Todays date is the 16th-

I project the outlook to look like this for the 25 th - 8 days away which is 192 at 00z tonight -

With one footnote- Because of the variabilty of the models & progression you can get over progressive models so if the same chart is replicated at 180 or 228 thats in the range of acceptance at this far out-

One final note-

when picking up prefect blocking- IE scandi or greenland the ensembles are hopeless- especially with a decent 2 or 4 wave pattern, the GFS ensembles cannot resolve the polar field very well so nearly ALL 4 ensemble suites are useless until day 5/6 approaches- before that expect the op to be outliers against the rest-

Ironically the ECM ensembles seem better at placing polar blocks...

In summary-

I ignore the 06z, but do watch the 18z for the laughter value,

I do discard the 12z ECM against the 12Z GFS *IF* I feel the GFS run is seemless in transition & looks more natural & the rest is gut instinct after the last 8 years of model ups & downs ( 11 years if you include snowatch)

S

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2012101618/gfsnh-0-114.png?18

If your looking for the trigger low its over SE greenland at 114 just developing....

S

[Geordiesnow]

Kinda ironic I was talking about a trend of pressure rising for us and the 18Z shows the UK stuck under the influence of low pressure! :lol: Does seem a little out of place mind in terms of how it develops and other trends but perhaps not as out of place as the ECM 12Z low pressure cell at 120 hours?

In terms of other parts of the run, it seems the PV in the Arctic is having a mind of its own at the moment, seems to be pushing any height rises into Canada even more so you would imagines parts of Canada and the western parts of the US will get yet another cold shot, cold air is more widespread across western parts of Russia and into Scandi than the 12Z so should boost some sort of snow cover around there. Be interesting if the GFS show a projected Northerly for the UK like the last run(and the run before that I believe).

[bluearmy]

just a comment re the gefs steve. they were upgraded in resolution in feb so we havent had a winter season to see if they are better across the polar field as yet.

[Met4Cast]

Why aren't the ensemble members run at the same resolution as the GFS Operational? Surely that'd give more accuracy within the ensembles suite? That is assuming the ensemble members are still run at a lower resolution..

[SMU]

So here is the first run @ 204 for the GFS

Classic omega Block- right up into the pole-

Deep low over scandi, Low to the SW & notice because of the high over canada ( 2 wave) then the low over the US is sandwiched in-

Good start on the forecasting front -

My critique would say its a bit to far south in terms of locale to where I think the high will be & also the 18z will be keen to drop the high away from the pole...

S

Edited October 16, 2012 by Steve Murr

[Met4Cast]

I don't know whats going on here

http://www.wetterzentrale.de/pics/Rtavn2881.png

[Snow and storms]

The forecast is great for mushrooms at the momment, the ground is lovely and soft, get picking before the big easterly comes

[swfc]

The forecast is great for mushrooms at the momment, the ground is lovely and soft, get picking before the big easterly comes

sorry.pity the high does slightly collapse later in the run but overall pretty good and in line with the12z

[SMU]

very good GFS Ensemble mean t 156

http://modeles.meteociel.fr/modeles/gens/run/gensnh-21-1-156.png?18

S

[SMU]

WOW-

PTB 3, 6, 8,9, 17,

http://modeles.meteociel.fr/modeles/gens/run/gensnh-6-1-192.png?18

All monsters

S

[Boro_andy]

Steve,

If your prediction on the previous page comes off, what are we likely to see in the uk?

I see blues so I understand this means it will be cold but specific conditions?

[Met4Cast]

More support from the 18z ensembles this time around

http://www.wetterzentrale.de/pics/MT8_London_ens.png

[summer blizzard]

I have no other word to say than shocking for the model output tonight, two GFS runs in a row suggesting the possibility of wintry showers (probably 100m+) as we enter November.

[chionomaniac]

The ingredients for a possible late month cold spell are certainly there but does the modeling have teleconnective back up?

This morning the GFS programs a deep Scandinavian low at around T + 180 ( just out of reliable) with a pressure rise over Greenland - probably the only way to drag cold air over the whole country at this time of year. This is probably too early in the season to give lowland snow (but we have recent experience of this in October so we can't rule it out).

The -5ºC 850's are even modeled later to reach the south coast:

Looking at the lower stratosphere profile the polar vortex is forecast to be slightly displaced towards the Russian / scandi sector on the ECM - so support here:

The MJO is forecast to be in phase 1 - this supports some form of northern blocking - but not necessarily a large Scandi trough, so we will need to await further modeling here.

The UKMO has a strong Scandi block in place at T+ 144 and I am dubious whether this could get replaced by a strong upper trough in 30 hours.

I will await the ECM with interest.

[lorenzo]

Looks like the ECM means business this morning in respect of that block you mentioned C, quickly flattening things out at days 6/7.

At 144..

UKMO / GFS / ECM

ECM 168 - 192

[Gibby]

Good morning folks. Here's my take on the 00zs for today Wednesday October 17th 2012.

All models show a deep Low pressure becoming slow moving near NW Britain over the next few days. It will fill slowly with the strong winds in the West decreasing over the coming 24 hours. A SW flow blows over most places with a trough close to the SE bringing the risk f rain here tomorrow as a disturbance runs NE along it.Elsewhere sunny intervals and scattered showers look likely in brisk SW winds but mild air will make sunny spells feel very pleasant. As the Low fills up by the weekend a slack flow could allow for mist and fog patches at the weekend which might be reluctant to clear before Low pressure moving up from the South on Sunday sees rain reach the South and march North later in the day.

GFS then takes this Low pressure North over Britain followed by a Southerly flow once more with Low pressure to the East and Low to the West. After rain clears the North Monday a couple of dry days with mild air and a lot of cloud looks likely. Later in the week Low pressure crosses the UK bringing heavy rain before a change to colder and clearer conditions move in through the latter end of the week with the winds turning Northerly and temperatures falling below normal. In FI cold and unsettled weather gives way to dry, frosty and foggy conditions as High pressure moves over the UK for the end of the run.

The GFS Ensembles show that once more the operational was big cold outlier at the end with the more likely outcome being a fall off from the mildness of the coming days to temperatures near to normal with drier weather from High pressure situated in a position that is conducive to less cold conditions than the operational. There is though enormous spread between the members in the final third of the run in locations North and south.

The Jet Stream shows a sharp troughing of the flow close to the UK before in a couple of days time the flow splits with a Northern arm well North of the UK with the Southern arm weakening with time South od the UK. The pattern becomes more diffuse and indeterminate in a week or so.

UKMO for midnight on Tuesday shows High pressure over the Baltic Sea with a mild and light Southerly flow over the UK. Mostly dry weather would likely prevail under a lot of cloud cover and temperatures above normal.

ECM shows a SE flow at the same time point backing towards the East late in the run with mild conditions gradually diluting to rather cooler weather with average temperatures in cloudy and misty conditions. Frost may develop in the North with time and Fog more generally if winds fall light enough and skies clear.

In Summary there is still some mouth watering options for an early blast of winter from the GFS operational. More realistically though the pattern is slowly becoming clearer. It looks like a mild Southerly flow with rather drier conditions will slowly back towards the East as we move through next week slowly lowering temperatures to normal late October values but maintaining quite dry conditions if cloudy and misty for many. Some areas could experience frost and fog by night but widespread problems look unlikely unless skies clear.