Model Output Discussion - Late October Onwards

[johnholmes]

CFS, be it the raw output or the other output showing monthly charts and expected anomalies is very very inconsistent. Having been running the Xmas forecast outlook using it over the past 7-8 weeks, I have yet to find ANY consistency in it whatever for the winter period

That is other than almost every run of the raw CFS, now some 40+ instances tend to show an unsettled winter is the most likely outcome. I don't keep copies from previous autumn outputs but I do not recall it getting anywhere near the correct idea for winter 2011-2011..

[shedhead]

They are in the netweather extra section Shedhead.

Thanks RD - also here for those not signed up to NetEx.... http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/

[damianslaw]

CFS, be it the raw output or the other output showing monthly charts and expected anomalies is very very inconsistent. Having been running the Xmas forecast outlook using it over the past 7-8 weeks, I have yet to find ANY consistency in it whatever for the winter period

That is other than almost every run of the raw CFS, now some 40+ instances tend to show an unsettled winter is the most likely outcome. I don't keep copies from previous autumn outputs but I do not recall it getting anywhere near the correct idea for winter 2011-2011..

Agreed, the CFS outputs yo-yo from week to week with different scenarios - I never bother looking at them.

Back to the models - expect very little change in the overall theme of things in the coming days with a very persistant pattern of high pressure to the east/southeast and lows tracking to the NW of the country thus leaving us in a predominantly SW flow. These set ups can become 'locked in' for lengthy periods, and tend to disrupt in sudden short-term timeframes, often catching the models out, so with this in mind unless there is a clear upstream signal suggesting a pattern change, don't expect the models to differ much in their output in the coming days with only slight variations on the pattern as shown now. I do rate GFS better than ECM in such situations it tends to project developments to our west and northwest much better than ECM. I do feel we will see a gradual erosion of heights to our east/southeast as we move through the first part of November and the trigger for a pattern change will be a deep low pressure system tracking on a more southerly course enabling a cooler northwesterly flow to develop - but it may take until mid November before we see such a change - as I said yesterday the synoptical output is very very normal for the time of year, now is not the time for looking for snow and cold, we are much more likely to see snow and cold in April than we are in late Oct/first half of Nov - the statistics show this. The chance of cold and snow increases markedly only when we reach mid November. In the meantime lets enjoy some traditional autumn weather.

Edited October 25, 2011 by damianslaw

[Radiating Dendrite]

Thanks RD - also here for those not signed up to NetEx.... http://www.cpc.ncep....wwang/cfs_fcst/

Yep.

I was referring to the daily synoptic outlook though (raw data). This is basically the next nine months, with the CFS producing a chart for every day.

Not sure if they can be accessed freely.

[Paul]

It's worth bearing in mind that the CFS raw data is not bias corrected, the correction is added in when the anomaly maps/forecasts are created, so it needs a bit more interpretation if you're wanting to glean anything from the daily maps.

[Rocheydub]

GFS predicting some nasty storms a week from now... Scotland and northern Ireland feeling it the most by the looks of it.

Surprised no one else has commented on this!

[wimblettben]

GFS predicting some nasty storms a week from now... Scotland and northern Ireland feeling it the most by the looks of it.

Surprised no one else has commented on this!

Probably because a lot of people are currently dissapointed at the poor outlook for cold weather.

Even if it did verify it would only be a Scotland and Northern Ireland event as usual.

[Liam J]

GFS predicting some nasty storms a week from now... Scotland and northern Ireland feeling it the most by the looks of it.

Surprised no one else has commented on this!

I am keeping a close eye these developments, things do look like turning very unsettled into next week possibly even stormy. to early to speculate on the detail at this stage. Some nasty weather is just around the corner, I predict a very active period as we enter November with the potential for severe wind events.

I'm being spoiled by some of favourite synoptic charts, far easier and less stressful than trying to hang onto the odd rare cold chart in FI

Edited October 25, 2011 by Liam J

[Stormyking]

Don't see why people would getting disappointed in cold not showing yet, still over a month to go until winter starts, to be honest I haven't seen many people dissapointed as of yet

I like the look of the models to be honest, I love autumnal storms with gales and heavy rain.

I think a little patience will be needed

[Thundery wintry showers]

The main reason why I didn't comment on it is that it's the 'wrong' side of T+168- I think, particularly with high pressure proving stubborn to the east, it may well be toned down somewhat as we get nearer the time. I agree with the references to the frequently one-sided nature of the discussions in here though- for instance today's convective/thunder potential for southern and south-western England has passed by largely unnoticed. Tomorrow looks set to have more widespread shower activity, though perhaps not as intense as some southern parts are having today.

[Rocheydub]

ECM is showing something similar though too. Strong possibility IMO.

[ITSY]

it seems as though in the space of just a few days, FI has gone from being almost exclusively dominated by HP to being dominated by various Atlantic Lows. Just goes to illustrate the point that, in the space of just a few days, anything can happen. Also, severe thunder here in Leeds atm

[kold weather]

I suspect strongly the ECM is going to be closer to the mark, afterlal we all know the GFS has a habit of being too far east and strong with these types of systems. Pattern is condusive for a strong LP in the Atlantic, I just happen to think the GFS in particular is slightly under-estimating the stubborn upper ridge that has held firm recently to our east.

[feb1991blizzard]

This could give a pasting to the higher ground of Northern parts, Unlikely to veryfy as the HP is too squeezed so very little margin for error and will be gone on next run and will be an outlier but all the same its model output and its showing snow so im going to post it.

http://hw.nwstatic.co.uk/gfsimages/gfs.20111025/18/288/h850t850eu.png

[Liam J]

GFS continues to show a very unsettled outlook on the 18z run, remaining fairly mild in the reliable time frame with some deep LP systems crossing the UK bringing strong winds and rainfall to many. It's looks like a cold outlier in FI and out of sync with previous runs and the other models so I wouldn't bother with anything past +192.

[kold weather]

Well an interesting 18z, shows what would happen if the upper high ends up weaker then it has been in recent times. Seems to be suggesting the pattern the ECM had a few days ago but has since moved away from.

240hrs would be a big snow-storm for the higher ground of Scotland though at this time of year low ground probably just on the wrong side of marginal if it came off...which it probably won't!!

[BlueHedgehog074]

Latest GFS does seem to be showing one or two odd Northerly outbreaks out in deep Fantasy Island, but I do feel that they are perhaps being a bit too progressive with trying to eridcate the blocking to the East, and as such, may program the Low-Pressure systems(s) to be further West in its furture runs. Too far West, and we'd probably end up with mild South-Westerly/Southerly winds.

ECMWF keeps the general wind direction throughout its run between the South and West - North-Western areas likely to see the most of the rain/showers, with the pressure Lower in these areas.

Edited October 25, 2011 by Rainbow Snow

[mushymanrob]

these anomoly charts would suggest the current ecm is closer to the mark then the current gfs (as kold weather suggested)http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

[johnholmes]

None of the 3 anomaly charts at 500mb show anything other than a continuation of things as they are. Unsettled with the upper flow mainly from south of west into the UK, so never cold other than in any temporary overnight ridge conditions. Brief swings of the surface flow into north of west MAY just cause some snow to fall on the highest parts of Scotland. Little sign into the first half of November of any major change either. Beyond that? We will have to wait and see how the longer term teleconnections develop to see if there is a signal for change.

[Gibby]

Good morning. Heres my take on the 00zs of GFS, UKMO and ECM.

GFS this morning shows a typical Autumn mix of mild and unsettled weather mixed with colder and brighter spells with sunshine and showers, these showers from the charts that are shown would fall as snow on Northern hills at times. With deep Low pressure close to the UK at times winds would reach gale force at times. It is true though this morning that charts do show quite a lot of cold air around at times bringing snow down to quite low levels in the North at times. In these colder interludes frost could occur at night.

The GFS Ensembles continue to show a fairly normal mix of wind and rain with near to normal uppers for late October and early November. There would be much more rain than of late reaching the SE throughout the run after the weekend. In Aberdeen a cold dip is shown as an outlier for a while but similar cold dips by other members are present so one could say it's not without support.

UKMO today shows the current Low pressure complex and attendant rain giving way from the South by Friday as a ridge develops and hangs on over the weekend for the SE. Further North and West renewed Atlantic Low pressure begins to dominate the weather with rain and wind developing Saturday then extending slowly SE to all areas early next week. temperatures would recover to near normal or above by then.

ECM gradually develops a mobile Westerly pattern with periods of rain and strong winds from a Westerly quarter. Temperatures would stay near to normal for the most part though it could be rather mild in the SE to start and rather cold in the North at times towards the end of the run.

In Summary nothing new to report this morning. Ignoring the detail of any individual run the models continue to show a typical Autumn pattern with showers or longer periods of rain mixed with brief drier and brighter interludes. Little in the way of significant cold weather looks likely while this pattern remains in place though the odd frost at night could occur under any clearer interludes.

Edited October 26, 2011 by Gibby

[Nick F]

Yes, ECM and GFS both agree this morning on the mean trough still to the W and NW by the 8-10day period:

So little hope for anything cold for a while yet, just the usual unsettled mixture as would be expected with cyclonic westerlies or southwesterlies.

The flow looks pretty flat and zonal upstream right back to the north Pacific too, so can't see much of a shift working through to change this pattern for a while.

[johnholmes]

Yes, ECM and GFS both agree this morning on the mean trough still to the W and NW by the 8-10day period:

So little hope for anything cold for a while yet, just the usual unsettled mixture as would be expected with cyclonic southwesterlies.

Yes as much as what one day shows its the consistency or otherwise that can lead to either a fairly reliable expectation or the opposite. In this case, all 3, as I posted above, have been reasonably consistent about the upper air pattern, for most of the past week. Equally they were also consistent in predicting the short colder spell of a few days ago.

[Glacier Point]

Yes Nick, the upstream pattern is being modelled by ECM and GFS ensemble mean as being very flat, the Pacific ridge being more sausage shaped which is preventing the amplification poleward and setting up what could well be a sustained phase of cyclonic activity in the Atlantic.

It's interesting to note that the mean position of the upper trough is exactly where it should be based upon previous years where we had a strong MJO wave passing through phases 8-1-2 in October. This appears to run through into the subsequent December pattern as well, the mean position of the trough only shifting slightly further NW.

[Richie V]

Yes Nick, the upstream pattern is being modelled by ECM and GFS ensemble mean as being very flat, the Pacific ridge being more sausage shaped which is preventing the amplification poleward and setting up what could well be a sustained phase of cyclonic activity in the Atlantic.

It's interesting to note that the mean position of the upper trough is exactly where it should be based upon previous years where we had a strong MJO wave passing through phases 8-1-2 in October. This appears to run through into the subsequent December pattern as well, the mean position of the trough only shifting slightly further NW.

Well I'm ready for a change this winter. Theres been a distinct lack of atlantic activity over the last 3 years. I'm actually quite excited of the prospect of a flat jetstream over the coming 3 - 6 weeks. Enhanced prospects for some quite stormy periods do you think? BRING ON THE SEVERE GALES!

[feb1991blizzard]

528dam 500mb-1000mb as far south as Southern England on latest GFS run.

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=276&mode=3

Edited October 26, 2011 by feb1991blizzard