Model Output Discussion; into 2015

[Nick F]

I think this deep low just to the south of Greenland is important if we are going to get cold and snow. If it develops just a bit further south than shown or even just weaker, I think the high pressure cell by the UK could then ridge into Greenland and latch onto the high already there. The low would then be forced to track much further south.

 

 

The flow at 500mb (roughly 16,000ft up) generally determines where surface lows and highs end up - the 500mb heights contours roughly show the direction of the 500mb flow and are shown by the colours on the chart below. Surface  Lows like the one near Greenland will generally follow the 500mb contour so will drift NE in this case. Also worth noting the upper trough above the surface low near Greenland will also push east sinking the high over the UK.

 

 

If the upper flow wasn't so strong behind this trough pushing east, then there would be more potential for the ridge over the UK to have more staying power and the trough arriving from the west to slow and develop a more negative tilt i.e. undercutting the ridge. But the strong zonal jet coming out of NE Canada is against this happening.

Edited January 2, 2015 by Nick F

[Jonathan Lang]

The flow at 500mb (roughly 16,000ft up) generally determines where surface lows and highs end up - the 500mb heights contours roughly show the direction of the 500mb flow and are shown by the colours on the chart below. Surface  Lows like the one near Greenland will generally follow the 500mb contour so will drift NE in this case. Also worth noting the upper trough above the surface low near Greenland will also push east sinking the high over the UK.

 

h500_su18z.png

 

But if the low was weaker, with weaker heights, wouldn't the high simply break through and cut off the aforementioned low? Also the amplification evident in the chart you showed means the high should have an easier time breaking through? Please bear with me as I am no expert and still learning.

Edited January 2, 2015 by Jonathan Lang

[Nick F]

But if the low was weaker, with weaker heights, wouldn't the high simply break through and cut off the aforementioned low? Also the amplification evident in the chart you showed means the high should have an easier time breaking through? Please bear with me as I am no expert and still learning.

 

Even if the surface low and 500mb heights were weaker, and at this close range - only could be slightly weaker, the positive tilt of the upper torugh pushing east (i.e. SW to NE aligned) the high over the UK will be unable to riddge NW against the west to east movement of this upper trough which has a strong upper flow pushing behind it.

 

If the chart you posted was date-stamped a week later, then there would be more scope for the models perhaps overestimating the strong flow and hence the flow would perhaps be more weaker and more amplified and prone to undercutting this ridge over the UK. In fact a a few days or more ago I'm sure we were discussing the potential for the ridge perhaps rasing heights over Scandi.

 

But at only 2 days away, it's very unlikely to pan out any different from what's shown given the very low Shannon Entropy with the predictable strong zonal flow.

Edited January 2, 2015 by Nick F

[Jonathan Lang]

Even if the surface low and 500mb heights were weaker, and at this close range - only could be slightly weaker, the positive tilt of the upper torugh pushing east (i.e. SW to NE aligned) the high over the UK will be unable to riddge NW against the west to east movement of this upper trough which has a strong upper flow pushing behind it.

 

If the chart you posted was date-stamped a week later, then there would be more scope for the models perhaps overestimating the strong flow and hence the flow would perhaps be more weaker and more amplified and prone to undercutting this ridge over the UK. In fact a a few days or more ago I'm sure we were discussing the potential for the ridge perhaps rasing heights over Scandi.

 

But at only 2 days away, it's very unlikely to pan out any different from what's shown given the very low Shannon Entropy with the predictable strong zonal flow.

 

But if you see my second post, this is not the only attempt the high makes of this. It happens more than once and we may prove lucky eventually. Low chance of happening but I think its something to watch.

[Captain Shortwave]

But if you see my second post, this is not the only attempt the high makes of this. It happens more than once and we may prove lucky eventually. Low chance of happening but I think its something to watch.

But the second chart is at 14 days out so the chances of the chart looking anything like that at a closer timeframe (for better or for worse) are very slim indeed. There are no real drivers at the moment for colder weather outside occasional bursts of polar maritime air as low pressure clears eastwards. This may improve by mid-month.

GFS coming out now, Saturdays low looks very much like a rain only event (away from some northern hills) with colder air not really breaching the southern half of the UK.

Sunday looks better and rather chilly with sunny spells.

Edited January 2, 2015 by Captain shortwave

[IDO]

But if you see my second post, this is not the only attempt the high makes of this. It happens more than once and we may prove lucky eventually. Low chance of happening but I think its something to watch.

 

 

We had the "will it wont it" saga about 4-5 days ago re that high you referred to on the first post. That has been a done deal for a while. There was a chance for that one to build as the synoptics led some credence to a MLB/HLB. However, as with the weather, things have now moved on and the jet is forecast to power off NE Canada for the next 10 days(+) so any subsequent baby ridge will be flattened unceremoniously. 

 

So no chance in the next 10 days plus for a high to build in the Atlantic/UK/Scandi region.

[Mucka]

The output and my thoughts very much the same for the last few days. 

The run toward mid month will likely produce some colder conditions as deep depressions slow to our NE creating deep trough into N Europe with UK on cold side of flow.

Possible heavy snowfall for some Northern parts around same period.

Atlantic ridge should develop behind this trough with another lobe of PV pushing W/SW amplifying the pattern upstream. These changes in the trop would appear to correlate with  predicted strat warming but I will leave that to the goodly strat folk to decipher. ECM threw out an op a few days back with similar synoptic but it was far too progressive with any possible pattern change and quickly dropped it.

 

So a window of opportunity around mid month for a pattern change but still very tentative at this stage. Over the next few days, other than some positive updates from Fergie on a strengthening signal of the zonal express being derailed, we need to see GFS ensembles firming up on the Atlantic ridge and strengthening it.

Edited January 2, 2015 by Mucka

[johnholmes]

I'm not sure what the time period is for the average days in terms of how many years data they include. In terms of extinct it was that way for quite a few years before that recent run of more snowier winters.

 

I know everyones patience is wearing thin which is totally understandable, lets see where we are early next week in terms of the NWP.

 

somply look on their web site for the days of lying snow it quotes the years the use, not sure but probably 1000-2010 as the latest, might be the period before that.

I think this deep low just to the south of Greenland is important if we are going to get cold and snow. If it develops just a bit further south than shown or even just weaker, I think the high pressure cell by the UK could then ridge into Greenland and latch onto the high already there. The low would then be forced to track much further south.

 

 

The surface feature is not the main part of the equation Jonathon it is the upper air pattern, so you need to look at what is showing along with the jet stream or the wind flow/contours at 300mb.

[Mucka]

A few deep FI mid month ensemble members showing the sort of signal we want to see strengthen. Deep trough to the NE, Atlantic ridge/displaced Azores high to the West.

Obviously there will be many variations at that range but there is clearly a weak signal for pattern change potential from around mid month.

Probably no more than 20% chance or a full pattern change currently but a better chance of UK at least being temporarily affected by colder weather in the run toward mid month with some heavy snowfall potential (13th to 15th inclusive looks about right)

 

I understand the pessimism because this is deep FI and the next 10 days look very poor for snow chances to low levels of England but this is not the interminable Atlantic onslaught of last Winter and there could well be heavy snow within the next two weeks for some. 

 

 

 

 

Caveats.

The Op and GFSp have generally been more reluctant to displace the Azores high with it playing spoiler and GFS ensembles can have a tendency to overplay cold potential from a trough having it dig too far South and correcting North as the time-frame nears.

That said I think coldies should still look more tot eh signal within the ensembles at that range while looking for the Op/GFSp to model something similar over the next 2 or 3 days.

Edited January 2, 2015 by Mucka

[Winter Cold]

Well 7 posts in 3 hours in the model thread in the depths of winter says all you need to know really!! Its a shame we are going to have to suffer the next 10-14 days of nothing wintry (at least)

 

I really hope one of Mucka's GEFS from above come to verify, as distant FI is all we've got to hold on to at the moment

 

ECM is late on Meteociel, just starting to trickle out now. I thought they decided not to run it as it wasnt going to show anything good anyway

Edited January 2, 2015 by Winter Cold

[Frosty.]

There are a number of 12z perturbations going for an Arctic spell around mid month. P9 would bring ice days and snow to all parts of the UK. If this is a sign of things to come, model watching could become even more interesting.

[Snowman.]

A few deep FI mid month ensemble members showing the sort of signal we want to see strengthen. Deep trough to the NE, Atlantic ridge/displaced Azores high to the West.

Obviously there will be many variations at that range but there is clearly a weak signal for pattern change potential from around mid month.

Probably no more than 20% chance or a full pattern change currently but a better chance of UK at least being temporarily affected by colder weather in the run toward mid month with some heavy snowfall potential (13th to 15th inclusive looks about right)

 

I understand the pessimism because this is deep FI and the next 10 days look very poor for snow chances to low levels of England but this is not the interminable Atlantic onslaught of last Winter and there could well be heavy snow within the next two weeks for some. 

 

 

 

 

Caveats.

The Op and GFSp have generally been more reluctant to displace the Azores high with it playing spoiler and GFS ensembles can have a tendency to overplay cold potential from a trough having it dig too far South and correcting North as the time-frame nears.

That said I think coldies should still look more tot eh signal within the ensembles at that range while looking for the Op/GFSp to model something similar over the next 2 or 3 days.

 

It's significant enough to affect the anomalies.

 

[Daniel*]

T240 ECMWF

http://www.meteociel.fr/modeles/ecmwf.php?ech=72&mode=1&map=1&type=0&archive=0

On a positive there are not many heights dropping to our S

and the PV transferring more to the east of the meridian line

[Pennine Ten Foot Drifts]

Aye, and rather bizarrely, the 'straw clutch' from T372 lat night, it's still there, and now at T336 !!! Bets on when it'll disappear ???

 

[Harsh Climate]

Aye, and rather bizarrely, the 'straw clutch' from T372 lat night, it's still there, and now at T336 !!! Bets on when it'll disappear ???

 

Rtavn3361.gif

 

 

I think the charts are looking up a bit now, small steps in the right direction.

[Frosty.]

Tonight's Ecm 12z op run looks flatter than the 00z, less polar maritime, more tropical maritime, high pressure over the south at times and lows zipping east between iceland and Scotland, midweek onwards looks particularly wet and windy across the north, the best of the fine weather in the south, more of a mix of average to mild rather than cold...not a run to linger in the memory.

Edited January 2, 2015 by Frosty.

[Captain Shortwave]

At day 8, the ECM and GFS show we really have a mountain to climb

ECM

GFS

Parallel

Well above average pressure over south west Europe. Lets hope it doesn't take an age to shift.

Backed up by the ensembles

Average pressure of 1040mb or higher, high amount of certainty on that high building in at the start of week 2.

 

GFS ens do suggest a cool down by the end of week 2, but still a long way off. The first half of January looks to be above average in terms of temperatures, lets hope the second half can at least bring this down to below average for the month.

[kev238]

If the charts that are posted above verify then it is a very long route to cold charts - they are as bad as it gets really if you are looking for cold and snow in the first 20 days of January.

Being objective, it does seem a long shot to believe there will be any long lasting snowfall in lowland Britain before the 20th of this month ( and that is being generous )

At least last winter had interest ( being a weather enthusiast ) whereas this winter could end up being a snooze fest for most of England devoid of any interesting conditions dominated by high pressure to the south

[nick sussex]

Trying to find some positives from tonights operational outputs upto day ten.

 

I maybe some time.......................................................

 

Okay I've waved the white flag! The operationals are all in agreement for a spell of mild mobile weather upto day ten, any signs of life re cold are showing up on a few GEFS ensembles but well into FI.

 

I think we're left with two options barring the emergency trip to Lapland , the MJO I'm actually more interested in than the current modelling and so we wait to see of this can survive and move into phase 7 at a decent amplitude. So far this winter its hit a brickwall ,  annoyingly at present even with this current strat warming Berlin Uni which has some key charts hasn't updated, the effect if any of that warming seems hard to quantify.

 

One of course could look at the PV and think what strat warming, I mean could the output have looked any worse anyway!

 

Whether theres some effect on the PV during the rest of January we'll just have to wait and see, of course waiting and patience seems the mantra that's been in evidence for the last 5 weeks for cold and snow lovers.

 

I think realistically we should just view the next ten days as likely to deliver little if any cold interest, I'm willing to give it to next week and then hope the output upto T240hrs begins to show a bit more interest if not expect to see a plethora of these clogging up my posts  .

[Frosty.]

The GEFS 12z mean trends colder between T+240 and the end of the run, another good sign. I think beyond mid month we could be looking at a wintry pattern.

[pdiddy]

If the charts that are posted above verify then it is a very long route to cold charts - they are as bad as it gets really if you are looking for cold and snow in the first 20 days of January.

Being objective, it does seem a long shot to believe there will be any long lasting snowfall in lowland Britain before the 20th of this month ( and that is being generous )

At least last winter had interest ( being a weather enthusiast ) whereas this winter could end up being a snooze fest for most of England devoid of any interesting conditions dominated by high pressure to the south

from the GFS in Nov 10, showing 18th Nov.  High pressure to the South...

I'll leave you to add the "what happened next"...

Edited January 2, 2015 by pdiddy

[nick sussex]

The GEFS 12z mean trends colder between T+240 and the end of the run, another good sign. I think beyond mid month we could be looking at a wintry pattern.

Which mid-month? February, March or next December! lol Frosty do you know those stages of grief I think you're stuck in denial, I've moved onto acceptance. :smiliz19:

 

You're turning into the Mary Poppins of NW, far too happy and optimistic, but you do make me laugh, you can always find something good in the outputs.

 

If something appears within the T240hrs timeframe then I might get a bit more interested, if not I'm going to maintain my current miserable stance!

[karyo]

from the GFS in Nov 10, showing 18th Nov.  High pressure to the South...

I'll leave you to add the "what happened next"...

It was November then and we had all winter ahead of us. Now we don't have that luxury.

[pdiddy]

It was November then and we had all winter ahead of us. Now we don't have that luxury.

That's right... we only have two thirds remaining.  The point was more related to the models showing a "long route to cold" based on "high pressure to the South".  My point (obviously) was that things can change quickly and did in Nov 10 based on that particular GFS run.  The poster was suggesting little chance of cold in the next 3 weeks...

[kev238]

Are you seriously suggesting the charts are similar ?

The charts posted by captain shortwave are as unfavourable to cold as you can possibly face a week into January if they verify - from there there is no quick route to cold despite your dubious November 2010 analogy