Model Output Discussion 4th Dec.2013-12z onwards.

[Beaufort12]

Blame the graveyard shift not me. Severe winds for my location Wednesday night if that was to verify

[Frosty.]

The Gfs 00z op run shows a more pronounced cold and unsettled spell during christmas week with rain, sleet and snow across the uk. In the reliable timeframe it's a very disturbed pattern during the next 5-7 days with severe gales and periods of heavy rain interspersed with clearer, colder and showery days with wintry ppn and snow risk, the snow generally further north and higher up but a distinctly wintry feel at times, accentuated by the strength of the winds and very little respite between those stormy atlantic systems..batten down the hatches guys, it's gonna be a bumpy ride.

[Gibby]

Good morning. Here is the latest report on the 12 midnight outputs of GFS, UKMO, GEM, NAVGEM and ECM for today Saturday December 14th 2013.

 

All models show troughs of low pressure crossing East across the UK later today and tonight in a strong SW flow. The rain will be heaviest in the NW and here will be coupled with severe gale force winds for a time. Clearer air behind the fronts will bring a quieter spell overnight before tomorrow sees a re-run of today as another swipe from Atlantic fronts affect all areas in a mild weekend and a stormy one over the NW. Early next week sees somewhat less mild conditions for a ttimes as pressure builds near the South with later Monday and tuesday becoming dry and bright. By Wednesday the next powerful Atlantic storm will of wound itself up to the NW with troughs swinging East with wind and rain for all by the end of the day.

 

GFS then shows a sustained period of Atlantic dominated weather with very deep low pressure to the North pushing active troughs and secondary Lows NE across all areas with spells of rain followed by sunshine and squally showers, wintry at times over the hills in the North. there seems little chance of sustained cold weather with a white Christmas unlikely away from higher Northern elevations. The end of the run leading out of christmas and towards the New Year looks unlikely at this stage to see any major pattern change from the generally wet and windy conditions in SW or west winds though it might turn rather colder from the NW.

 

UKMO shows a blustery west wind behind a cold front next friday with a mix of sunshine and showers, wintry on Northern hills briefly before it looks like milder weather will return over the weekend as a new Atlantic system bears down on the UK from the West.

 

GEM shows a mild and windy spell of weather following a briefly chillier showery period late next week. Winds will be gale force and with fronts straddling the UK there would be rain at times for all, always heaviest across the North with some drier and very mild periods in the SE.

 

NAVGEM also shows a milder period next weekend as the cool and showery weather late next week becomes replaced by gale SW winds and warm frontal activity bringing rain NE across all areas next weekend.

 

ECM maintains very unsettled weather with the potential for a viscious storm system crossing the UK next weekend with storm force winds for a time and heavy rain followed by a mild SW flow with rain at times in the north and West and still windy weather everywhere.

 

The GFS Ensembles show a very unsettled and windy spell over the coming two weeks with a domination of Low pressure over or just to the North of the UK. After a mild start temperatures will moderate to average and perhaps slightly below average later with wintry precipitation developing over the hills at times.

 

The Jet Stream continues to show a sine wave pattern in a very strong flow near the UK for the next week or so. there are still indications this morning that the flow may sink South of the UK in week 2 increasing the risk of colder conditions over the UK later.

 

In Summary there seems little change in the overall windy and changeable theme of the weather over the entire period. the only main difference or trend seems to be that the South could become quite close to high pressure again over Europe for a time later next week decreasing the effects of rain and wind here and making it become quite mild again before it seems that it may well become wet and potentially stormy again over christmas week when Northern high ground could see some snow. Overall though the chances of a white Christmas remain quite slim though with Polar maritime air present close by a few may have a surprise.

[Purga]

Mild, wet & windy for most with some wintryness on northern hills at times maybe sums up the main NWP this morning.

Looking to FI there is a cooling trend

 

Illustrated well by the latter GFS 0z charts

 

At least showing some lower heights getting into mainland Europe - but that's a long way off.

 

ECM at 240hrs hints at high pressure over Europe giving a cool continental drift maybe as per the METO longer ange forecasts

A few crumbs but not much and certainly very zonal in the reliable timeframe

[IDO]

UKMO 12z yesterday has been ditched this morning with the PV at the moment too strong for potential ridging north, though I suspect this is a repeating scenario and may eventually be possible: 

 

Edited December 14, 2013 by i'm dreaming of...

[bluearmy]

UKMO 12z yesterday has been ditched this morning with the PV at the moment too strong for potential ridging north, though I suspect this is a repeating scenario and may eventually be possible: 

 

UN144-21.gif

 

very similar pattern - just adjusted ne somewhat. 

 

plenty of differing options in fi gefs. many split vortices on view. strange considering how strong it looks.  

[shedhead]

Little if anything in the way of change across the overnight model suites, with a very unsettled, locally stormy spell of weather to come. As is always the case in this kind of set up the north and west will bear the brunt of the wind and rain, but given the strength of the Jet timing each individual system will be problematic, as will nailing down the details on track and intensities.  Still a small window of opportunity for something colder and more seasonal on the big day, but up until then it looks set to be on the mild side generally, especially across the south.

[IDO]

The trend in FI is to push the Jet south, not total support with the GEFS but a clear trend, the ens highlight the cooling:

 

 

Looking at the GEFS mean in FI we see a strong MLB over the Pacific/W.Conus:

 

 

Allowing the jet to weaken and maybe allow for something more meridional: 

 

Like last night's 12z, the 0z control hints at the potential for this scenario; cool UK setup:

 

 

The GEFS stamps show no sign of any HLB or the HP to our south re-establishing:

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=384

 

Whilst the very cold uppers are well to our east and west this UK trough is probably our best bet in the medium term for something seasonal.

Edited December 14, 2013 by i'm dreaming of...

[johnholmes]

the anomaly charts have over several days gone to a 4 major trough set up around the northern hemisphere. This often tends to be a fairly long lasting set up, certainly 7-10 days and sometimes a good deal longer. As ba and shed have posted above there is nothing to suggest in the synoptic models any change in the run up to Christmas, unsettled and increasingly so further south seems to be the forecast, with short colder bursts behind each deep low on its western edge before the next system comes in. Just what will change this setup beyond Christmas I am not able to say. This pattern as I've suggested can be quite long lasting, edging east or west a few degrees without any major change. Currently NOAA has shifted the far west ridge (off the west coast of N America) about 5-10 east. Not sure if this is something that will continue. Sometimes one of the secondary lows becomes so deep it actually develops its own major trough which disrupts the previous 4 trough set up, sometimes just as a temporary feature, sometimes it is a major pattern change. No way for me to predict if/how/when this might happen in the current set up.

Edited December 14, 2013 by johnholmes

[Cloud 10]

A very significant LP anomaly (almost off the scale) west/north west of the UK as we head

towards christmas week which will likely create some drama in here,and busy times ahead

for the met office!

 

naefs..  ecm..

 

 

 

My call for christmas is "high pressure will not dominate" 

[winterof79]

The further north the better over the festive period.

At least frost will become a common occurance

http://modeles.meteociel.fr/modeles/gens/runs/2013121400/graphe3_1000_269_49___.gif  Ooop Yorkshire

http://modeles.meteociel.fr/modeles/gens/runs/2013121400/graphe3_1000_311_170___.gif  Further Sarf 

[Summer Sun]

3 nasty looking lows on this mornings ECM after this weekend

 

 

UKMO at t120 doesn't have the low as deep as ECM's 955mb low

 

Edited December 14, 2013 by Summer Sun

[radiohead]

image.jpg

I presume you mean the ECM, and it doesn't look that bad at all on Wednesday??

 

[AWD]

That be on Thursday, way in FI. Edited December 14, 2013 by AWD

[fergieweather]

image.jpg

I presume you mean the ECM, and it doesn't look that bad at all on Wednesday??

UKMO agrees, at least for now. They've modified GM to shift low centre on Weds further NW; MOGREPS isn't keen on anything too developed anyway, hence Exeter currently run with 20-25% chance of something disruptive developing (i.e. re winds).

[radiohead]

That be on Thursday, way in FI.

 

It's 0Z Thursday with the low located north of the posters location, so the strong winds shown by that model would have impacted on Wednesday, and those are very strong winds indeed. Not backed by other models though.

[snowmadchrisuk]

UKMO agrees, at least for now. They've modified GM to shift low centre on Weds further NW; MOGREPS isn't keen on anything too developed anyway, hence Exeter currently run with 20-25% chance of something disruptive developing (i.e. re winds).

Probably safe to say the further North you are the higher the chance of any significant winds . Mind you latest GFS shows it could get rather Windy in our part of the world, Bristol Channel would be a bit choppy .And again with another Low on Saturday , With an angry Atlantic surely one will be a direct hit soon . 

 

 

Edited December 14, 2013 by snowmadchrisuk

[gottolovethisweather]

For folk, wondering about the more immediate timeframe, they need not look any further than the thread below.

 

http://forum.netweather.tv/topic/78733-possible-severe-atlantic-storm-saturday-14th-december-2013-onwards/?p=2861706

 

 

Some fantastic input in there as mentioned   and yes, today's windstorm looks to be the first of many to effect the North and Outer Isles over the coming days.  That's not to say parts further down South aren't vulnerable to some fairly punchy gusts at times too. From a brief glance at the various NWP outputs, the windier spells look likely to be especially Sunday, Wednesday into Thursday and next Friday currently.

Edited December 14, 2013 by gottolovethisweather

[legritter]

Some hints on GFS of possibly a pressure rise on the russian arctic side in the far off outlook .still a very disturbed atlantic dominated flow next week ,and if pressure over eastern europe and further s /east falls more than forecast an even more stormy spell of weather .i think we will have to wait untill this evenings runs or even tomorrows to see if the ECM storm will come off later next week .some possible cold air being brought south around the festive period but at 12 days away who knows ,so a very interesting time a coming and the plot thickens gang .

[snowmadchrisuk]

Some hints on GFS of possibly a pressure rise on the russian arctic side in the far off outlook .still a very disturbed atlantic dominated flow next week ,and if pressure over eastern europe and further s /east falls more than forecast an even more stormy spell of weather .i think we will have to wait untill this evenings runs or even tomorrows to see if the ECM storm will come off later next week .some possible cold air being brought south around the festive period but at 12 days away who knows ,so a very interesting time a coming and the plot thickens gang .

 

Hmmm P/V sliding SE Pressure rising to the North , Best chance of a Scandi High I seen for a while, just maybe we are starting to see the possibility of a pattern change ... Hopeful thinking for now but still nice to see a possible we are starting to see a light at the end of the tunnel, still 11 days till Xmas. 

[fergieweather]

Hmmm P/V sliding SE Pressure rising to the North , Best chance of a Scandi High I seen for a while, just maybe we are starting to see the possibility of a pattern change ... Hopeful thinking for now but still nice to see a possible we are starting to see a light at the end of the tunnel, still 11 days till Xmas.

Latest 10-15d analysis just issued from UKMO prefers "no significant change" of type through that period, albeit with temporary/transient cooler/less mild periods & equally, transient ridging possible to SE. The M-R forecaster tells us "confidence is high in the general synoptic type" and concludes by noting a return to average temperatures may occur by end of period, at least in the N, due to veering of the flow to broad westerly. Edited December 14, 2013 by fergieweather

[Downpour]

UKMO agrees, at least for now. They've modified GM to shift low centre on Weds further NW; MOGREPS isn't keen on anything too developed anyway, hence Exeter currently run with 20-25% chance of something disruptive developing (i.e. re winds).

Good news Ian. Like many I'd rather spend the holidays drinking wine and watching the cricket than fixing my fence again! Edited December 14, 2013 by Downpour

[fergieweather]

Good news Ian. Like many I'd rather spend the holidays drinking wine and watching the cricket than fixing my fence again!

Ah... no, what UKMO mean by no change of synoptic type is that you may well have to tackle fence repair, but hopefully not in 5" of lying snow and sub-zero temperatures!!

[Long haul to mild]

Good news Ian. Like many I'd rather spend the holidays drinking wine and watching the cricket than fixing my fence again!

Yes, really pleased to see the models generally backing away from the dramatic fare served up by last night's GFS. I know everyone has their favourite type of weather but quite why anyone would want to see widespread structural damage, endangerment to life and thousands affected by power cuts just before Xmas is quite beyond me!

[nick sussex]

Interesting to see that the UKMO have high confidence in their outlook going forward. Taken at face value I think that looks okay given the model trends to day ten, after this I think theres more of a question mark.

 

The reason for this IMO is the situation in the eastern Pacific re any ridging there and the effect this might have on the PV.

 

Unusually we find both the GFS 06hrs run and the ECM 00hrs in broad agreement for the NH pattern at day ten:They both agree on that east Pacific ridge extending further towards the Arctic with troughing digging a little further south over the UK.

 

We're still seeing some slowing of the zonal winds in the strat towards the pole, whilst its unlikely we're going to see a sudden explosion of heights there still a chance that this could develop sufficiently to help divert the jet further south.