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

[Great Plum]

Obligatory daft GFS low in early FI shocker...http://www.wetterzentrale.de/pics/Rtavn2281.png

And then a real monster at the end...http://www.wetterzentrale.de/pics/Rtavn3841.pngHa!

[draztik]

MetO have been suggesting for a few days now that unsettled weather was likely to dominate as we progress through December, and certainly the GFS 12z concurs. Banging the drums in loud voice this afternoon. Rain totals a real concern for Northern areas, esp Scotland.

Edited December 9, 2013 by draztik

[fergieweather]

 

And then a real monster at the end...http://www.wetterzentrale.de/pics/Rtavn3841.pngHa!

... albeit in fairness, both EC and MOGREPS ensembles lately also contain some very deep lows of similar stature, so nothing can be discounted for now.

[Summer Sun]

Some concerning rainfall totals for NW Scotland showing currently

 

Getting on for 125mm by the 17th for some and another 80mm to 100mm from the 18th to 25th

 

[on the coast]

 ... albeit in fairness, both EC and MOGREPS ensembles lately also contain some very deep lows of similar stature, so nothing can be discounted for now.

 

Could be this Christmas may well be remembered for its storms rather than cold. Showing on alot of runs now in FI.

[Summer Sun]

GEM also looking stormy at t240 though its not overly cold

 

 

GFS at t240

 

 

This mornings ECM at t240 also showing some stormy weather

 

 

The Daily Express are already reporting on this saying Britain is on alert for another battering from fierce storms next week It will bring 70mph gales to many areas next week, with 90mph gusts threatening exposed northern regions.

[mountain shadow]

There remains the hope the big storms modelled around Christmas track a little further South and get East of the meridian.

With the cold locked up at the moment this may release some surprise snow for Christmas Day.

[legritter]

I think at this moment in time looking at current charts and data any cold will come from areas of low pressure passing to our north .But at the current range its  going to take a more southerly jet or high pressure over Europe to relax current conditions .Hopefully some of these lows can make it further south and east ,and i would say there is a fair chance of this happening .GFS looking stormy in its later output ,lets hope tonights ECM is a good one ,cheers 

[pip22]

TBH I don't think the next thursday storm if its verifies won't be as bad as last week, but still enough to uproot few trees though. We had 100 mph last time. I could be wrong.

Edited December 9, 2013 by pip22

[Gael_Force]

By the law of averages it was only a matter of time before we saw a throwback to some of those zonal mild spells of past winters. Perhaps recent winters have skewed what its realistic to expect in the UK during winter.

 

I think the best possible out of the current state of the NH pattern re the vortex is that we see a return of the Aleutian ridge and a little more amplification, so some PM air or at very best a northerly toppler.

 

If people are looking for a lengthy cold spell this is going to become very frustrating as its hard to see where a sustained HLB might come from, we're only in early December theres a lot of winter left so I think its going to have to be a patient wait to see what happens later into the season.

 

I'm not really surprised to see this when I'm firmly of the belief that the recent cold winters were triggered by a long and very low solar minimum (some think ice loss- better this year but overall still very low) - what is not low is solar activity, at maximum now, is it a coincidence that we are seeing this flatter pattern and potent vortex; I think not

[jvenge]

I'm not really surprised to see this when I'm firmly of the belief that the recent cold winters were triggered by a long and very low solar minimum (some think ice loss- better this year but overall still very low) - what is not low is solar activity, at maximum now, is it a coincidence that we are seeing this flatter pattern and potent vortex; I think not

Don't want to pick an argument on my first post, but can you back that up? I mean, as far as I know the Sun is currently at a 400 year minimum. What's your source to say its at maximum?

[Severe Siberian icy blast]

I'm not really surprised to see this when I'm firmly of the belief that the recent cold winters were triggered by a long and very low solar minimum (some think ice loss- better this year but overall still very low) - what is not low is solar activity, at maximum now, is it a coincidence that we are seeing this flatter pattern and potent vortex; I think not

I agree that the solar input has an effect on the weather and jet stream, but this winter has many other factors that has led to this spell , west QBO phase in a solar maximin been one of many , with the Asian snow advance really pegged far to the east through November , it's a slow burner this year. But all the signs point to change from the middle of jan , maybe a SSW late jan . Patience

[Duane S.]

Don't want to pick an argument on my first post, but can you back that up? I mean, as far as I know the Sun is currently at a 400 year minimum. What's your source to say its at maximum?

 

Maximum in terms of what is generally expected of SC24 I assume?

[Gael_Force]

Don't want to pick an argument on my first post, but can you back that up? I mean, as far as I know the Sun is currently at a 400 year minimum. What's your source to say its at maximum?

 

It is currently at the maximum of the eleven year cycle; the overall cycle is the lowest for hundred years or thereabouts.

[jvenge]

It is currently at the maximum of the eleven year cycle; the overall cycle is the lowest for hundred years or thereabouts.

Fair enough. As long as we agree that although it is at a "maximum" that maximum is fairly low compared to historic data.

[shedhead]

Both the GFS and UKMO 12 runs really start to fire up the Atlantic, the former being significantly more active than it's 00 predecessor and far more in line with this morning ECM. Will be very interesting to see if the 12 ECM now maintains or even develops the unsettled theme still further. 

Edited December 9, 2013 by shedhead

[Mucka]

Current output is reminiscent of that long run of mild winter outputs we had before 2009 with absolutely no sign of HLB.

Current GFS ensembles don't show a single run right out to Christmas day where cold air is established over the UK let alone widespread snowfall prospects.

Looks very unlikely we will see a white Christmas unless we see some major new developments appear for Christmas week.

 

Even the weak signal for a mid Atlantic ridge seems to have been washed away from the output for now so it is case of patience and fingers crossed for the foreseeable.

Things can and do change quite quickly and unexpectedly sometimes so let's hope for one such occasional and for some seasonal weather around Christmas,

 

Otherwise it is a slow sinking of the Euro high that has been giving us the mild and settled conditions for the most part and change to cooler unsettled regime over the next week or so with the South hanging on to the settled weather the longest .

Edited December 9, 2013 by Mucka

[bluearmy]

the movement of the vortex added to the push into the atlantic of that brutal cold over the states was always going to ramp up the northern arm next week. with the block quite solid to our south and east the possible squeeze on pressure is going to be big and these deep lows passing just nw of the uk have been a strong spread theme late next week on ecm and naefs. for once, gfs is probably not overdoing things and somewhere across the uk is likely to be pulling the short straw on this one. (maybe more than once).very little tropospherically to hang a coldie hat on today. the ens amplifications are fairly transient where they occur. the odd member more sustained amplified but the NH profile pretty awful in general if you want a cold outlook. i note joe b's tweet re strat situation but looking at gfs op modelling today, i see the output as less interesting than yesterday. i suspect he has view of ecm ens and gefs strat data so i bow to his 'greater knowledge'. we will see.

[jvenge]

the movement of the vortex added to the push into the atlantic of that brutal cold over the states was always going to ramp up the northern arm next week. with the block quite solid to our south and east the possible squeeze on pressure is going to be big and these deep lows passing just nw of the uk have been a strong spread theme late next week on ecm and naefs. for once, gfs is probably not overdoing things and somewhere across the uk is likely to be pulling the short straw on this one. (maybe more than once). very little tropospherically to hang a coldie hat on today. the ens amplifications are fairly transient where they occur. the odd member more sustained amplified but the NH profile pretty awful in general if you want a cold outlook. i note joe b's tweet re strat situation but looking at gfs op modelling today, i see the output as less interesting than yesterday. i suspect he has view of ecm ens and gefs strat data so i bow to his 'greater knowledge'. we will see.

Fair. However, correct me if I'm wrong, even if the stratosphere is warming, I believe it will take around 3 weeks to impact anything here? Again, that's assuming it is indeed happening as reported.

[Weathizard]

Just had a quick look through all the charts and ensembles - YUK! One of the worst and most stubborn patterns being projected & another one of them is currently ongoing(MLB). Looking shocking for coldies as has been said and the zonal pattern with strong vortex over Greenland is just dirge, worst type of winter weather for me, I'm not sure I can find any crumb of comfort, not even a little crumb...

[lorenzo]

Think Joe B has been following the activity on the 30hPa CPC plot as this is included in his tweet. Not sure if there is anything else making him so positive about how the strat will unfold.

Still warming on the edges of the vortex, and it is looking solid, the zonal wind profile is frightening, hence my call to send in the nukes. ECM at day 10 and it is ramping along at 100 ms-2. Temps from early in GFS run then FI.

 

Though these were worth sharing in the spirit of the festive season and in celebration of being bathed in African southerly air.

EC32 / weeklies / monthlies - yes they have three names, for final week of December.

 

Ensemble 2 please from here, perhaps a displacement.

 

The block attempts this throughout the run, but it really is the vortex that is in charge here, no doubt. Edit ; Sorting images.

 

 

 

 

 

 

Edited December 9, 2013 by lorenzo

[Summer Sun]

ECM still keen on developing something more unsettled as we move into next week though it never gets overly cold

 

[Tamara]

Its easy enough to see even by day 4 there is quite some temperature gradient beginning to spill out into the atlantic as deeply cold air spills out of the Canadian arctic and meets the air from the sub tropical ridges to the south. On that basis, secondary lows to the main body of the polar vortex, such as the one forming here on the ECM 12z, are starting the beginnings of making their presence felt on a track that is taking them ever closer to NW parts of Scotland, even though at this stage they are brushing still on a track that swings them more towards Iceland

 

.

 

 

We have seen a gradual tendency commence in the models for the High pressure regime to the south and east be eroded as the vortex to the NW begins to take ascendancy on the pattern. No coincidence that the METO outlooks are starting to revise their predictions accordingly with more unsettled weather looking to take control with time - at this stage more so the north and west, but to the extent that the previously suggested inversion highs over the south and east maybe are looking less likely as tropical maritime air from the atlantic becomes more extensive. .

 

There is every reason to suppose that this trend might accelerate further over the coming few days with the lead up to the Christmas period increasingly vigourously mobile, wet and windy. 

 

By day 7 the ECM 12z is further consolidating this trend with the trajectory of the secondary lows looking more organised on a track closer to NW parts and pressure is falling further south east as high pressure loses it grip

 

 

So, with the UKMO and GFS supporting this more progressive theme, it seems more inevitable that a spell of flatter atlantic driven weather is likely. Its a case of waiting to see how long it is before the jet stream, which is much more pre-disposed these days to being meridional with split flow, starts to revert the pattern upstream in the Pacific, and in turn amplifies the atlantic profile accordingly once more.

 

The most likely trend closer to the festive period is for the unsettled westerly pattern to gradually draw the heights to our south further westward and assist some further transitory polar maritime incursions - but we best not expect anything more than this. At least for the foreseeable future

 

The period from the 18th to the 20th maybe when this might start to be incoming. Its taking the output at face value of course, but the 12z ECM is following GFS suggestions for a similar time - with the atlantic already starting to take on a rather more amplified profile. So just maybe the euro High stuck pattern might not last too long - even though it is a long way back to anything properly cold. We should also bear in mind the propensity of the models to sometimes over amplify the pattern in the longer time period - so best not to expect any colder incursions to get too far south

 

Edited December 9, 2013 by Tamara תָּמָר

[bluearmy]

 

Fair. However, correct me if I'm wrong, even if the stratosphere is warming, I believe it will take around 3 weeks to impact anything here? Again, that's assuming it is indeed happening as reported.

 any significant warming is around three weeks away anyway. (assuming one actually occurs). the effects in the trop can be a quick response within a week or two, followed by further reversals several weeks later and again a few weeks after that. add to all of this that not all warming downwell to the trop and even if they do, we in the uk are not always best placed to receive deep cold.

[snow mad]

Interesting 240 chart is this the start of some blocking from the east. early days hopefully a new trend http://www.meteociel.fr/modeles/ecmwf.php?ech=240&mode=1&map=1&archive=0