Model output discussion 25th Jan - The final third of winter beckons..

[snowray]

2 hours ago, Iceaxecrampon said:

00z

Class.

Ppn just sits there on the East Coast.

One to watch if the blocking loses out -  then showtime.....

Plenty of easterly activity in FI  - but thats FI

Story of recent winters that chart of course.

Surely our luck is due to change, all important 12z runs today awaited with trepidation, but I am pretty sure that the rollercoaster has only just started out on this ride and there are going to be a lot of ups and downs still to come.

 

[snowray]

1 hour ago, stotm said:

The models run the numbers and they don't seem to programmed that the BOOM charts setup we like to see doesn't  happen very often . The programmers  don't seem to be able to stop them playing with these outputs in the 5 day plus range . They could use the U.K. as good block on rogue runs to help there forecasts for the rest of the world, if it's very cold and snowy then it's wrong 90 percent of the time conversely correct for anything else 90 percent of the time.This is just the way it seems to me, hopefully the models will be correct sooner than later with a BOOM chart, about 3 times every 10 years? Not saying it's not this time. 

 

Agree with you 100%. 

 

GFS 06z ensembles. Gone is the -6/-7 upper mean, but still some very cold runs in there.

[Frosty.]

Sigh of relief, the mild end to the Ecm 00z doesn't look likely, instead it looks like becoming progressively colder from the east from next midweek onwards with frosts becoming more widespread and cold crisp days, especially further east..get the cold air in place etc..

[Weathizard]

2 minutes ago, snowray said:

Agree with you 100%. 

 

GFS 06z ensembles. Gone is the -6/-7 upper mean, but still some very cold runs in there.

Was just going to say this, the 06z mean is a move away from the bitter 850's but we need to see whether the trend continues because the ensembles aren't that useful in these scenarios IMO - ironically the 6z ens suite shows bitter cold after day 10!

[Nick F]

Seems the operational runs this morning have come to some broad agreement for mid-to-late next week over how far west the cold pool advecting west out of western Russia reaches and also its southern extent too. with the  coldest T850s toward NE UK, though a look at the 06z GEFS, fair few members advect deep cold further south too (see below at T+144 / next Thursday), so by no means is this area resolved.

This uncertainty re: advection west of deep cold initially is related to rather active cyclogenesis around the positively-tilted deep upper trough extending down across the N Atlantic from Labrador/Greenland early-mid next week, with a few deep dartboard lows swinging NE then N around the upper trough toward Iceland - which limits the westward extension of the of Scandi high.

But the cyclogenesis to the west eases later next week, as a chunk of the 500mb vortex/low height over N Canada/Labrador/Greenland breaks off and moves SE toward SW Europe, with a more negatively-tilted upper trough extending SE on the SW flank of the block over Scandi - which will aid CAA westward again.

And it's at this juncture going forward will decide the destiny for whether we:

a)  BEST SCENARIO - see the Scandi high continue strong and in situ with enough low pressure extending east through the Med from Iberia to prevent the high sinking and to continue the deep cold air advecting west from Russia toward the UK -->

b) WORST SCENARIO (like 00z EC high res) - we see an upper trough cut-off and isolate over SW Europe/NW Africa - which will allow the Scandi ridge to weaken and extend/drop south while merging with an Azores ridge extension across the UK from the  west while Atlantic low pressure pushes east over the top toward Scandi

OR SOMEWHERE IN BETWEEN THE ABOVE OF COURSE

However, those worried about the likelihood of 00z ECMWF high res (above) evolution coming off, look at the EPS z500 and mslp mean and spread shows a fairly high standard deviation for the upper low over Greenland to push east toward Scandi, so could the high res could be too progressive in the area

Also, we saw a flip earlier in the week, think it was between the 00z and 12z operationals on Tuesday, which advertised the cold pool coming out of Russia still way to the east for 12z Weds next week, then the  12z brought the deep cold pool with -10C T850 line pretty much knocking on the east coast. Which goes to show that there may well be more twists and turns on the way from the model output as they come to terms with how to evolve the Atlantic trough disruption against the block over Scandi and how much energy to send underneath across southern Europe - which in turn determines whether the Scandi high keep in situ or sinks and how much deep cold gets advected west.

Still not a done deal this morning's operationals, though I suppose the high res should be ahead of the ensembles for z500 pattern up to day 7, beyond I would revert to ENS.

Edited February 3, 2017 by Nick F

[bluearmy]

21 minutes ago, Iceberg said:

11 of the 20 runs bring 850s of around -10 into central England. That's a very strong signal. 

Re ops if you get ops for a whole days of runs going consistently against the ens mean I would favour the new ops trend. However we've not really seen that yet. 

A good example of the ens being more useful is the strong low pressure system al la Doris progged by the ops. Ens didn't provide more than 30% support for them and it looks like the ens were right and the ops largely wrong. 

I think that's a bit of  an exaggeration ice.  for the midlands, I can only find 5 runs taking uppers below -9 by day 10. Once I get to Scotland I can get to 10. looking at the tabular format on meteociel which is every 6 hours.

If you are saying how many runs are generally sub -3c  thoroughout to day 10 then I would agree with your assessment. 

it just seems we are heading towards the moderation of the extremes as usually happens on the modelling. Given the overall pattern it should be great for wisdespread snowfall (though amounts very unclear). however, I just feel that without a direct strike from an upper cold pool, we are going to be scratching around. Hope I'm wrong of course 

[Geordiesnow]

I think the problem we are seeing here is too much focus is on the details of each run and in this type of set up, any detail change could mean quite a difference in terms of how cold the uppers will actually be.

I think the main trend I can see is that the weather should start to turn drier and more settled with the potential for some overnight frosts in places, potentially severe frosts if it sets up correctly. I really don't see snowfall being an issue at the moment as none of the models are really indicating its going to be a convective easterly as thicknesses and to a lesser extent pressure is too high for instability to form. I do think a Southerly/SE'ly drift from the continent looks the most likely to happen and whether we actually see a true easterly and a convective one remains to be seen although at this stage it looks unlikely I say.

[nick sussex]

I know of course all eyes are on the easterly drama but earlier Meteo France have issued a Red Warning which is exceptionally rare for parts of sw France.

Wind speeds could get close to 160km/h in coastal areas in those depts effected. To show how narrow the band of destructive winds is you can see here how you go from red to orange to just a yellow advisory over a relatively small distance. I'm in the yellow bit but still am feeling a bit concernced to say the least especially as theres a few members here who live towards that orange/red zone. Nouska who you see posting quite regularly seems to be close to the red area.

 

 

[TEITS]

All im going to say is the 06Z has made me nervous. The simple reason isn't just because of the 06Z GFS but the GEFS control aswell. Combine this with the ECM and its a worrying trend. Im not interested in what the other ensembles suggest because I cannot be a hypocrite and only side with the ensembles when it suits me. We could have 15 ensemble members showing -15C uppers but it means sweet FA if the operationals do not back this.

[Frosty.]

This could be a prolonged cold spell we are looking at with plenty of time for snow to make an appearance..The Ecm 00z ensemble mean looks very nice if you are a coldie like I am!

[northwestsnow]

8 minutes ago, TEITS said:

All im going to say is the 06Z has made me nervous. The simple reason isn't just because of the 06Z GFS but the GEFS control aswell. Combine this with the ECM and its a worrying trend. Im not interested in what the other ensembles suggest because I cannot be a hypocrite and only side with the ensembles when it suits me. We could have 15 ensemble members showing -15C uppers but it means sweet FA if the operationals do not back this.

Me too.

We really need some upgrades over the next few runs teits.

Trouble is once the ops find a less promising solution they tend to stick to it,for a meaningful cold spell upgrades are needed, the meto update continues to underwhelm ..

[nick sussex]

I think the modelling is likely to turn into a battle of the PV regrouping after the recent strat warming and the MJO which is continuing to progress with higher amplitude.

The easterly looks a bit more shaky today in terms of whether this is going to be a more se flow with the outputs chopping and changing, the GFS 00hrs was better early worse later and then the 06hrs better later worse earlier.

More uncertainty arrives with whether trough disruption will clear energy away to the west allowing the ridge to back west over the top.

So overall a lot of uncertainty still, chances for snow remain however and also some very cold temps.

[Frosty.]

17 minutes ago, northwestsnow said:

Me too.

We really need some upgrades over the next few runs teits.

Trouble is once the ops find a less promising solution they tend to stick to it,for a meaningful cold spell upgrades are needed, the meto update continues to underwhelm ..

At least it's going to become cold enough for snow which is important and frosts will become widespread..better than mild mush any day! Generally the models support a cold outlook.

Ps..I had a laugh when I read that most of north America can expect a mild February and early spring.. haha

Edited February 3, 2017 by Frosty.

[Seasonality]

9 minutes ago, northwestsnow said:

Me too.

We really need some upgrades over the next few runs teits.

Trouble is once the ops find a less promising solution they tend to stick to it,for a meaningful cold spell upgrades are needed, the meto update continues to underwhelm ..

I know it must feel like that. But is it not more so that the UK tends towards less cold outcomes so these end up being "better modelled" whereas colder weather for the UK is simply always the less likely solution. 

Alternatively we could reverse the earth's rotation to give the UK a climate like Sakhalin. 

[blizzard81]

6 minutes ago, nick sussex said:

I think the modelling is likely to turn into a battle of the PV regrouping after the recent strat warming and the MJO which is continuing to progress with higher amplitude.

The easterly looks a bit more shaky today in terms of whether this is going to be a more se flow with the outputs chopping and changing, the GFS 00hrs was better early worse later and then the 06hrs better later worse earlier.

More uncertainty arrives with whether trough disruption will clear energy away to the west allowing the ridge to back west over the top.

So overall a lot of uncertainty still, chances for snow remain however and also some very cold temps.

The means show a south easterly is the likely outcome in around 8 days time. This is ok as long as we get some fronts coming in from the south west and stalling right over my house lol. Some of our biggest and best snowfalls come from such scenarios. 

[East_England_Stormchaser91]

40 minutes ago, blizzard81 said:

The means show a south easterly is the likely outcome in around 8 days time. This is ok as long as we get some fronts coming in from the south west and stalling right over my house lol. Some of our biggest and best snowfalls come from such scenarios. 

Yes, February 2012 on the 4th delivered a very good snow event here. On a chart that has been posted sometime previously, you wouldn't think it would have done. Uppers were not outlandish at all at around -3 to -5, but the fact that it was a clean feed off the continent and low dew points, meant that we hit the jackers. Next week is looking very similar, if not better. 

Edited February 3, 2017 by East_England_Stormchaser91

[blizzard81]

2 minutes ago, East_England_Stormchaser91 said:

Yes, February 2012 on the 4th delivered a very good snow event here. On a chart that has been posted sometime previously, you wouldn't think it would have done. Uppers were not outlandish at all at around -3 to -5, but the fact that it was a clean feed off the continent and low dew points, meant that we hit the jackers. Next week is looking very similar, if not better. 

Indeed. From the trends so far today, I think this is the best we can hope for. The chances of a convective easterly have faded significantly today.

[East_England_Stormchaser91]

14 minutes ago, blizzard81 said:

Indeed. From the trends so far today, I think this is the best we can hope for. The chances of a convective easterly have faded significantly today.

Indeed they have. 

The main thing however and the key foundation is getting the cold air here first, then that foundation can be built upon regarding snowfall. It's often the little surprises such as flash disturbances and shortwaves that can cause unexpected dumpings of snow. January 2010 was an example when a very shallow polar style low moved south over the south Midlands and into the western Home Counties and gave nearly half a foot of snow! 

This I believe was it. 

Edited February 3, 2017 by East_England_Stormchaser91

[Frosty.]

12 minutes ago, East_England_Stormchaser91 said:

Indeed they have. 

The main thing however and the key foundation is getting the cold air here first, then that foundation can be built upon regarding snowfall. It's often the little surprises such as flash disturbances and shortwaves that can cause unexpected dumpings of snow. January 2010 was an example when a very shallow polar style low moved south over the south Midlands and into the western Home Counties and gave nearly half a foot of snow! 

Fully agree, thankfully the outlook from next midweek onwards looks increasingly cold and blocked..mild swly mush well and truly banished!

In the short term, there could be some hill snow across the Midlands and northern england tonight as colder air digs in from the west.

Edited February 3, 2017 by Frosty.

[Severe Siberian icy blast]

42 minutes ago, nick sussex said:

I think the modelling is likely to turn into a battle of the PV regrouping after the recent strat warming and the MJO which is continuing to progress with higher amplitude.

The easterly looks a bit more shaky today in terms of whether this is going to be a more se flow with the outputs chopping and changing, the GFS 00hrs was better early worse later and then the 06hrs better later worse earlier.

More uncertainty arrives with whether trough disruption will clear energy away to the west allowing the ridge to back west over the top.

So overall a lot of uncertainty still, chances for snow remain however and also some very cold temps.

Nick the warming was only this wk, the scandi high is trop fed which has bought an immediate wave 2 up into the strat which is the cause for the split vortex, the effects from the ssw  is in my opinion still 10-20 days away depending on its ability to downwell  (or not). 

[blizzard81]

13 minutes ago, East_England_Stormchaser91 said:

Indeed they have. 

The main thing however and the key foundation is getting the cold air here first, then that foundation can be built upon regarding snowfall. It's often the little surprises such as flash disturbances and shortwaves that can cause unexpected dumpings of snow. January 2010 was an example when a very shallow polar style low moved south over the south Midlands and into the western Home Counties and gave nearly half a foot of snow! 

This is all well and good but we need the current trend to slow down. With the atlantic forcing at days 4 & 5, this trend could accelerate so we do not get enough continental air in so everything stays as rain. We have gone from a possible fail safe option of a very cold convective easterly to a very risky high stakes option that could now go either way.

Edited February 3, 2017 by blizzard81

[Ali1977]

So what we looking for in the 12z, I personally think the Ops may improve again, more inline with the ENS anyway - we seem to lose continental flow around day 8 however so I'd be surprised if that doesn't happen.  We may start seeing PV break up in deep FI too IF the SSW start showing its hand, just a shame we can't hold onto the Scandy high till then - or can we.

Edited February 3, 2017 by Ali1977

[Anon90]

One thing I've been meaning to ask  since unfavourable trend started a day or so is it to with the Strat suddenly not looking as good or more to do with the dice not rolling in our favour post the warming effect?

[Mucka]

Well that went downhill fast.

 

The very cold -8/-10 runs on GFS ensembles have all but vanished too

Lot's more energy in the Northern arm with the high pushed further East and less favourably aligned with  jet generally over the top does not a good cold spell make so hoping for a turnaround this evening.

 

 

 

 

Edited February 3, 2017 by Mucka

[warrenb]

13 minutes ago, Mucka said:

Well that went downhill fast. Shockingly ECM Op was among the coldest runs.

The very cold -8/-10 runs on GFS ensembles have all but vanished too

Lot's more energy in the Northern arm with the high pushed further East and less favourably aligned with  jet generally over the top does not a good cold spell make so hoping for a turnaround this evening.

 

 

 

 

The top chart is wind speed in metres per second