Model output discussion - 5th December 2016 - Into Winter we go

[knocker]

Before a quick look on where we stand regarding the two lows this weekend just a note of the jet stream as it's touching 180Kts.

This morning sees the first depression between Iceland and Scotland 960mb by 1800z on Friday. The main band of storm force winds will be just north of Scotland but the Hebrides and the far north do not escape altogether with 80Kt gusts briefly impacting there and obviously still very windy with gales and blizzards on the hills/mountains of the far north.

This depression quickly clears and equally quickly the next one rushes in to be 967mb north east of Wick by 12z Sunday. The track of this low would bring some very strong winds to Scotland, particularly the central belt, with gusts of 70kts plus. Needless to say apart from the very strong winds and snow in the vert far north some very wet conditions over the weekend for everyone with the south.south east escaping the worst.

Looking further ahead sees the amplification of the high pressure as has been indicated by the anomalies with the HP ridging to our SE and troughs disrupting out west

Edited December 20, 2016 by knocker

[Ali1977]

Finally after a week of dross the ENS are really starting to look up in FI, Some real good charts among them with plenty showing the Atlantic high ridging north towards Greenland. 

[ArHu3]

big changes for ecmwf  already after only 72h compared with yesterday (the christmas eve and pacific depressions downgraded and moved quite a bit)

Edited December 20, 2016 by ArHu3

[mcweather]

23 minutes ago, Ali1977 said:

Finally after a week of dross the ENS are really starting to look up in FI, Some real good charts among them with plenty showing the Atlantic high ridging north towards Greenland. 

Yes rather like happened at the beginning of Dec after after the meto contingency forecast went for cold and blocked and the longer nwp went for mild now the update has gone for basically mild the longer term gefs at least start to trend chillier and blocked. One should remember that Ian F did state at the start of his posts last night that there was very low confidence in the on going monthly and seasonal outputs so writing off winter on the basis of something even the professionals have little confidence in seems a tad premature to  me.

[Seasonality]

I can understand the positivity. After the 18z I raised an eyebrow but now the 00z has flipped too I'm interested. Amplification is back in the operational. For my holiday period in Warsaw I'm delighted. Look at the snow row, back in action after some utterly miserable output showing almost nothing. Good news too in the ridging, potentially headed in a good direction for the uk and cold uppers back over Warsaw by 192h when previously it was flat as a witch's proverbial. 192h is not reliable of course but not mad FI either.

Edited December 20, 2016 by Seasonality

[Captain Shortwave]

Well a bit of progress from the ECM this morning.

At least the high is getting a bit further north to allow some cooler and drier air push in from the continent.

GFS/GEM for the same time

   

Decent agreement on this with a sharpening Atlantic trough and cold air pushing well south into eastern and south east Europe. So an increasing chance of a settled end to the year after some wind and rain around Christmas with the chance of the high getting far enough north to cut off any mild Atlantic flow. I can also see the high backing west a bit aided by low heights becoming cut of towards the Azores later on.

Edited December 20, 2016 by Captain Shortwave

[Seasonality]

Good news everyone. The ECM has read the script and has also amplified. Again charts from the 192h period I discussed in my previous post. Don't believe anyone who tells you the models don't "flip back to cold."

[Gustywind]

High pressure ridging up towards Scandi at 192h on ECM, colder uppers flooding into Scandi and E Europe.

[Seasonality]

8 minutes ago, Gustywind said:

High pressure ridging up towards Scandi at 192h on ECM, colder uppers flooding into Scandi and E Europe.

Ridging continuing towards Scandi at 216. Cold heading west.

[Captain Shortwave]

Well I would probably take this if it verified.

  

Whilst there are similarities to where we are now and have been for a week or so, the upstream pattern is a lot better and would offer better scope to pull the high northwards enough to possibly allow colder air to filter in from the east. Namely the sharper trough over the United States which allows a ridge to build through Newfoundland and the western Atlantic as opposed to the steamroller we are currently about to see push relentlessly eastwards as we approach Christmas. Still it is a day 10 chart but at least some steps in the right direction, especially that we could push beyond the Euro high scenario and not stall with relentless mild (Dry SE/mixed NW) southwesterlies.

Anyway if there is one point regarding the output this morning and the trends on offer, it would be this. This relentless and endless zonal barrage (which could last until January/February/December 2094 etc etc), will not even last a week. 

Edited December 20, 2016 by Captain Shortwave

[Seasonality]

240 not ideal I admit but loads can change at that range. Definitely better news overall from the midnight runs.

[mb018538]

Well I wasn't expecting a rebuild of high pressure so soon after xmas! Most unexpected! But I'll take it over wind and rain any day!

[knocker]

It continues to be very annoying but I keep getting different outputs from the models that many others seem to be getting. Quite baffling. Anyway

 

Edited December 20, 2016 by knocker

[West is Best]

These two storms are starting to look potentially very serious. I have a feeling the Christmas Day one could be worse because of its evolution and slightly more southerly track plus the 'whip in its tail.' However, both are showing damaging gusts. Not brilliant timing in terms of the festive season

23rd/24th:

Christmas Day:

 

 

Edited December 20, 2016 by West is Best

[IDO]

Pretty poor run by the GEFS this morning. The D16 charts are low key: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=384

Split 60:40 UK HP or zonal. This suggests that the interlude at D8 where the Azores rebuilds over the UK is not looking like any sustained rise; mid-latitude at best. The PV remains mobile so upstream any meridional flow is brief as the PV shifts around.

I think it is hard not to conclude that this late Autumn to early Winter we are in a locked in pattern where there is limited forcing so HLBs are just not happening in the NH. The Azores -v- PV is the UK picture and as the latter grows with time the chances of the Azores pushing further north diminishes. Plenty of cold air to mid latitudes so I am sure we will get a whiff of that now and then, but modified PM air is not everybody's cup of tea. London ens suggest we are going to see anomalous high uppers from Christmas Day, associated with that  euro/uk ridge. Depending on its travel could be some nice weather. 

All the models are in the same ball park re long wave pattern; just a case where the core euro high sits:

D10: 

Christmas Day looks like being very mild for the south, but with a westerly flow so cloudy, though maybe 13c? Cooler as you move NW as a brief cold pool moves in led by the cold front. At the moment the hi-res only go to the start of Christmas Day but as expected the initial front will be rain, Birmingham North:

 

 

Edited December 20, 2016 by IDO

[West is Best]

6 minutes ago, IDO said:

 

Christmas Day looks like being very mild for the south, but with a westerly flow so cloudy, though maybe 13c? Cooler as you move NW as a brief cold pool moves in led by the cold front.

 

 

That's rather an understatement about the cooler pattern, if I may say so. At the moment the -5C 850hPa is shown pushing into southern Britain during the evening. This certainly isn't mild, let alone very mild:

Personally, and with this much  synoptic movement I wouldn't like to forecast timings on that briefer warmer interlude as firmly as you with 5 days to go.

Edited December 20, 2016 by West is Best

[ArHu3]

1 hour ago, Seasonality said:

I can understand the positivity. After the 18z I raised an eyebrow but now the 00z has flipped too I'm interested. Amplification is back in the operational. For my holiday period in Warsaw I'm delighted. Look at the snow row, back in action after some utterly miserable output showing almost nothing. Good news too in the ridging, potentially headed in a good direction for the uk and cold uppers back over Warsaw by 192h when previously it was flat as a witch's proverbial. 192h is not reliable of course but not mad FI either.

I think we need to wait until after Christmas because small changes to the track and intensity of those depressions cause very big changes later on

[Seasonality]

2 minutes ago, ArHu3 said:

I think we need to wait until after Christmas because small changes to the track and intensity of those depressions cause very big changes later on

You're 100% right @ArHu3. Forgive me if I sound excited, my feet are still planted firmly on the ground but I do love it when a favourable change occurs after such dull output. What is promising though is at 192h most of the ensembles show the amplification with a decent number of cold options down the line. So much dependent on the depressions as you say.

[mb018538]

11 minutes ago, West is Best said:

That's rather an understatement about the cooler pattern, if I may say so. At the moment the -5C 850hPa is shown pushing into southern Britain during the evening. This certainly isn't mild, let alone very mild:

Personally, and with this much  synoptic movement I wouldn't like to forecast timings on that briefer warmer interlude as firmly as you with 5 days to go.

Not really? The comment was referring to xmas day itself....which at the moment, is forecast to be 13/14c in the south : http://www.bbc.co.uk/weather/2643743

There may be some cooler air tucking in behind....but that nay well be after the sun had gone down, so won't affect the maxima for the day. Perhaps a cool night and cooler boxing day. Anyway, the average max for London in late December is 7c, and the BBC forecast has every day for the next 10 between 8-14c, so all above average. Hardly cold!

[Nick F]

Sense of déjù vu from EC day 10, with the Euro high extending north, I suppose eventually we'd get a chilly but dry continental flow.

At least the GFS and EC ops both agree on amplification upstream in the day 7-10 period, it's then whether the trough amping out west can stall as a standing wave or continues east that controls the destiny thereafter.

With the strat PV forecast to get as strong as last winter at 10 hPa and a definite strat-trop connection, the outlook painted by the ops in the medium range could be worse, given weak tropical forcing signal from MJO/ENSO and the low AAM. GEFS has over the last few days been hinting at MJO coming out of COD into low amplitude 7/8/1 into early Jan, but EC and other models are yet to pick up on this.

At least the Xmas day storm doesn't look so bad on EC det this morning, Friday night storm looks worse. GFS looking bad for both storms. So still some uncertainty re: track and depth of Xmas day storm, Friday night storm may affect the evolution and intensity of Xmas day storm following hot on its heels.

Edited December 20, 2016 by Nick F

[Seasonality]

Before any usual suspect beats me to it. Here is a 384h mean chart, I mean this proves conclusively we're stuck in zonal until the end of time does it not? Of course not, it isn't much use in the current discussion and I DOn't know of any real use for it but there it is, just in case anyone tries to trot it out in a meaningful manner.

 

[West is Best]

1 minute ago, mb018538 said:

Not really? The comment was referring to xmas day itself....which at the moment, is forecast to be 13/14c in the south : 

The point is that the colder air is pushing south on the day itself.

I'm certainly not able to forecast the timing with 5 days to go but the evening looks far from mild. It's just a little careless to describe the whole day as 'very mild' when there is forecast to be a temperature drop as it progresses. The timing will be interesting. 

Much synoptic movement, with serious storms ahead, mean even greater uncertainty about timings.

[bluearmy]

Surprised to see the surprise at the ECM op today. It ends with the high anomoly a few hundred miles north of where the eps had it yesterday and the pattern virtually bang on. perhaps the amplification on the way to where it ends has cheered some up but that may be a bit overstated and thus the end point a few hundred miles north of the mean from yesterday's 12z. Either way, sceuro ridge, se uk favoured drier than nw uk overall is the eps story for now and generally supported by the GEFS although they are trending the MLB west and seeing a scrussian trough appearing on their 00z run. 

at least the six weeks of zonality some promised may now be less relevant for much of the uk though as we know, that probably doesn't mean wintry conditions. 

[carinthian]

No real change in the forecast chart for the big day from the UKMO. No cruel deep winter charts for most including the Eastern states of the USA , looks like a warm flow on this chart up to the Great Lakes. Hopefull;y not too far beyond the Christmas Period we will see the stubborn high pressure zone relocate to a postion further North or West so we can tap into some real winter charts.  Still early days yet and its just amazing that the promise of full throttle zonal charts just spin the lows north with no real impact against the Euro block for many folk in Euroland and Southern Britain. Just to cheer you all up , Sweden and Norway had some temps around 10c yesterday .

 C

Edited December 20, 2016 by carinthian

[Banbury]

As I pointed out last night but the post got removed , this is ideal, if we cant have snow this is the next best think, it will be chilly , and of course always the chance of relocation

Edited December 20, 2016 by Banbury