Model Output Discussion - cold spell to end Autumn

[karlos1983]

10 minutes ago, Singularity said:

 

Slight shift south from the ARPEGE 06z, what a shame it stops at +72 eh? 

Given this and the 00z ECM and allowing for typical uncertainties, it seems the low centre could yet go anywhere between Cornwall and the Scottish border. Helpful, I know 

That is the ultimate tease...... I was ready to throw in the towel, maybe 1 more round of false hope eh 

NAVGM on same page as Aperge

Edited December 7, 2017 by karlos1983

[Mike Poole]

46 minutes ago, Man With Beard said:

EC 00Z clusters

T96:

5 clusters at D4 lol!! Does seem a growing consensus not to phase the slider too quickly and more agreement on a track a bit more to the SW (good call if right SM!!), which would pull the snow-risk zone south a bit.

T192:

Very good agreement clearly on a fresh Atlantic ridge but looks minor at this stage - weak NWly on its back, snow is going to mount up on high ground...

T240:

A slight shift from last night - looking to flatten out, still in a NWly flow for the UK but Atlantic high anomaly dropping (need more runs to find continuity)

T300:

Seems like a shift to the Atlantic but watch the NE corner on cluster 1 - is an eastern block going to form? Otherwise cluster 2 is westerly dominated, and cluster 3 (minor cluster) is wintry with blocking west and north

T360:

Atlantic too strong on cluster 1 so block to east doesn't happen, but northern heights still in evidence on all three charts.

All in all - there is general much more doubt over a longer term cold set-up, with the Atlantic showing much more energy than of late between D10-D15 - but it's not a complete ensemble flip and bearing in mind this is slightly at odds with previous ensemble runs, it merely increases the uncertainty of what will come after a fresh northerly at D8/D9. 

For me, the most interesting new tool in our model analysing armoury this year are these Icelandic ECM cluster plots, as often posted (and well explained) by MWB. 

Although the pictures for each cluster cover rather small area of the globe, at the risk of stating the obvious, more information is provided by the colour of the border.  These correlate to the four broad patterns at the bottom of the graphic.  The first two are obvious – the others needed Google translate:

Blue: +NAO

Green: –NAO

Red: Fyrirstada translates as ‘obstruction’ – I’m guessing ‘Scandinavian Blocking’?

Mauve: Hryggur initially translates as ‘sorry’!  But if you get the other meetings, includes ‘spine’ and ridge’ – ‘Atlantic ridge’?

The percentages next to these, vetrarmisseri = Winter Term, likur = probability, the middle word doesn’t translate – I guess these are the seasonal likelihoods from climatology.

Edited December 7, 2017 by Mike Poole

[Glacier Point]

Not wanting to labour a point here but..

Day 15 GEFS tees us up perfectly.

I think this being a more fair reflection of probabilities than the 06z op.

The question from here is entirely Pacific side. The expectation being the ridge over the NE Pacific to discontinuously retrogress and separate pulling the PV westwards, allowing the mid and upper flow over the Atlantic to head south and east. Probabilities for the timing of this would be higher the closer we get to January.

Edited December 7, 2017 by Glacier Point

[bluearmy]

31 minutes ago, Singularity said:

 

Slight shift south from the ARPEGE 06z, what a shame it stops at +72 eh? 

Given this and the 00z ECM and allowing for typical uncertainties, it seems the low centre could yet go anywhere between Cornwall and the Scottish border. Helpful, I know 

But it couldn’t really go anywhere near the scottish borders? No model has shown this over the past 48 hours.  Can’t see the low centre tracking se much north of Carlisle  and the probability is strong it will be heading into n Ireland and then disrupting se towards se england - the cone widens as it leaves n Ireland to be somewhere between Lincolnshire and Cornwall imo 

i am thinking Carlisle isn’t far from the Scottish Borders but as the system slides  se it doesn’t have enough easterly momentum to go ne at all. 

Edited December 7, 2017 by bluearmy

[Singularity]

4 minutes ago, bluearmy said:

But it couldn’t really go anywhere near the scottish borders? No model has shown this over the past 48 hours.  Can’t see the low centre tracking se much north of Carlisle  and the probability is strong it will be heading into n Ireland and then disrupting se towards se england - the cone widens as it leaves n Ireland to be somewhere between Lincolnshire and Cornwall imo 

Okay you got me, maybe I've seen one too many 'where did that come from?' moments in my time and was being overly cautious there. I'd only give a track that far north a 1% chance at this stage. Maybe 2% if I'm feeling generous .

Interesting thoughts from GP this morning. They make a lot of sense (obviously) but going full-faith does require shaking of some hammered-in inhibitions from recent winters... oh how I want to though so I could just settle down and enjoy watching it all come along and unfold!

Edited December 7, 2017 by Singularity

[Derecho]

Guten tag

So as I expected this weekend is all over the place but the overall long term pattern is pretty consistent. Here is the pattern developing next week.



So cold across the UK with a wintry mix with the potential for more low pressure coming in from the west, with low pressure forming just to the east of Greenland. However high pressure could build behind it. Here are the scenarios that could develop:

                       1:  40%                                                           2:     15%                                              3:   30%
   

Potential development from 1st scenario



So I think we may see attempted ridging to Greenland shown in scenario 1, leaving the UK in rather cold temperatures. The high may start persisting to our NW or could wax and wane leaving low pressure to pass through. If the blocking starts building to our NW then this could lead to a more negative NAO pattern though that's a bit of a distance away. It would finally encourage much colder air to start appearing to the far east. 

The second scenario is that the pattern remains stuck with a similar pattern to next week persisting into the future. Again cold and seasonal.

The final scenario is something milder, a risk if the polar vortex starts shifting east, hopefully that won't happen and we have a week of colder weather at least so enjoy . I still think heights over Scandi may occur too.

Edited December 7, 2017 by Quicksilver1989

[Methuselah]

19 minutes ago, bluearmy said:

But it couldn’t really go anywhere near the scottish borders? No model has shown this over the past 48 hours.  Can’t see the low centre tracking se much north of Carlisle  and the probability is strong it will be heading into n Ireland and then disrupting se towards se england - the cone widens as it leaves n Ireland to be somewhere between Lincolnshire and Cornwall imo 

i am thinking Carlisle isn’t far from the Scottish Borders but as the system slides  se it doesn’t have enough easterly momentum to go ne at all. 

Maybe not, technically, but quite close though: the less-cold air is almost up to the Firth of Forth.

Edited December 7, 2017 by Ed Stone

[Iceaxecrampon]

1 hour ago, karlos1983 said:

Hold your horses Daniel, I was merely commenting on the one run that is churning out. Don't start on me just because the GFS has shown a more northerly track! Try living down south where we celebrate a frost!

 

 

....without being drawn in to the bunfight and before it inevitably gets deleted - you do have the benefit of such wonderful summers of which we have so much enyoyed for the last 17 years

[bobbydog]

27 minutes ago, karlos1983 said:

That is the ultimate tease...... I was ready to throw in the towel, maybe 1 more round of false hope eh 

NAVGM on same page as Aperge

don't be throwing any towels yet karlos, we won't know the precise track of this 'slider' until around 12 hours before. LP systems rarely follow the predicted track this far out. 

if it does, i'll eat my hat.

not that i've got a hat.

but if i did have a hat, it would be made of cake, in case i have to eat it...

(much better mood this morning )

[Glacier Point]

9 minutes ago, Singularity said:

They make a lot of sense (obviously) but going full-faith does require shaking of some hammered-in inhibitions from recent winters... 

I think if we were going down that route, we would not being seeing what we are now (particularly w/r/t observed -AO, stratospheric forecast for the core of the cooling season, and, observed similarites with the evolution from 2005/6, 1995/6, ad some other years I care not to mention). For us to deviate from the current path, we are going to need to see a dramatic turnaround in modelling [to a more +AO/+NAO]. Still possible, but becoming increasingly unlikely IMO

[lawrenk]

27 minutes ago, Glacier Point said:

Not wanting to labour a point here but..

Day 15 GEFS tees us up perfectly.

I think this being a more fair reflection of probabilities than the 06z op.

The question from here is entirely Pacific side. The expectation being the ridge over the NE Pacific to discontinuously retrogress and separate pulling the PV westwards, allowing the mid and upper flow over the Atlantic to head south and east. Probabilities for the timing of this would be higher the closer we get to January.

Labour the point as often as you like GP.

No complaints here!

[Mark Bayley]

23 minutes ago, bluearmy said:

But it couldn’t really go anywhere near the scottish borders? No model has shown this over the past 48 hours.  Can’t see the low centre tracking se much north of Carlisle  and the probability is strong it will be heading into n Ireland and then disrupting se towards se england - the cone widens as it leaves n Ireland to be somewhere between Lincolnshire and Cornwall imo 

i am thinking Carlisle isn’t far from the Scottish Borders but as the system slides  se it doesn’t have enough easterly momentum to go ne at all. 

Tbf the JMA does - although not exactly a beacon of reliability 

 

Edited December 7, 2017 by Mark Bayley

[Singularity]

  

Hmm. Not sure how effective this 2 km variant of WRF-NMM those 40-50 cm readings over the mountains of northern Wales and Scotland are impressive. Depends on showers training heavily though, forming some quite narrow streamers.

[Timmytour]

16 minutes ago, Quicksilver1989 said:

So cold across the UK with a wintry mix with the potential for more low pressure coming in from the west, with low pressure forming just to the east of Greenland. However high pressure could build behind it. Here are the scenarios that could develop:
   

.
 

Just wondered if I was alone in seeing this and immediately adopting the French art character Rowan Atkinson played in  a famous Not The Nine O'Clock News sketche....

"A Greenland high?  Pah!   That is not a Greenland High!   It is, instead, a giant willy...."

 

[Singularity]

10 minutes ago, Glacier Point said:

I think if we were going down that route, we would not being seeing what we are now (particularly w/r/t observed -AO, stratospheric forecast for the core of the cooling season, and, observed similarites with the evolution from 2005/6, 1995/6, ad some other years I care not to mention). For us to deviate from the current path, we are going to need to see a dramatic turnaround in modelling [to a more +AO/+NAO]. Still possible, but becoming increasingly unlikely IMO

Thanks for the reply GP 

I am far more on-side than not with regard to the evolution you suggest so it's not going to take a lot more for me to do whatever the opposite of throwing the towel in is .

Those other years, I think I know which ones you mean . I have been tracking similarities for an extended period and at times they have been eye-catching.

[bluearmy]

21 minutes ago, Glacier Point said:

I think if we were going down that route, we would not being seeing what we are now (particularly w/r/t observed -AO, stratospheric forecast for the core of the cooling season, and, observed similarites with the evolution from 2005/6, 1995/6, ad some other years I care not to mention). For us to deviate from the current path, we are going to need to see a dramatic turnaround in modelling [to a more +AO/+NAO]. Still possible, but becoming increasingly unlikely IMO

The gefs and eps AO forecasts becoming increasing neutral through week 2 on last couple runs 

[bluearmy]

30 minutes ago, Ed Stone said:

Maybe not, technically, but quite close though: the less-cold air is almost up to the Firth of Forth.

It’s not about uppers though ed - it’s about other things with sub zero uppers required 

 

[bluearmy]

20 minutes ago, Mark Bayley said:

Tbf the JMA does - although not exactly a beacon of reliability 

 

Fair enough mark - it’s not right though !

[Methuselah]

1 minute ago, bluearmy said:

It’s not about uppers though ed - it’s about other things with sub zero uppers required 

 

Aye, ba, I'm fully aware of that.

[Glacier Point]

18 minutes ago, bluearmy said:

The gefs and eps AO forecasts becoming increasing neutral through week 2 on last couple runs 

Not sure how fully useful those two indices will be given January's likely pattern and spatial temperature anomalies.

Given December's AO is going to be around -1.5 SD, suggestion is that January value will be around -0.5 to -1.0. Correct that temperature analogue accordingly....

[bluearmy]

1 minute ago, Glacier Point said:

Not sure how fully useful those two indices will be given January's likely pattern and spatial temperature anomalies.

Given December's AO is going to be around -1.5 SD, suggestion is that January value will be around -0.5 to -1.0. Correct that temperature analogue accordingly....

Noted Stewart but I was looking at the last sentence of your post where you referenced a flip to a positive AO/NAO and the current direction of travel is in that direction although still unconvincing and without enough consistency (yet)

[West is Best]

1 hour ago, karlos1983 said:

That is the ultimate tease...... I was ready to throw in the towel, maybe 1 more round of false hope eh 

NAVGM on same page as Aperge

I have to say, that I think this is the form horse. It depends how quickly and deeply the arctic air entrenches. But this doesn't look to me like an east-west trajectory at all. I wouldn't be all that surprised if only Devon and Cornwall see the precipitation to be frank. It has happened before. Infamously, if I recall, on 5th-6th February 2009 when right up to the last minute the MetO and all models were predicting the incoming low to sweep across southern Britain and the Midlands. In fact, only Devon and Cornwall copped it:

https://www.theguardian.com/uk/2009/feb/06/cars-stranded-devon-snow

I was fortunate enough to be there at the time and it was magnifique  Here you go with the charts. Look at all familiar?

 

Edited December 7, 2017 by West is Best

[MattStoke]

Just when we think the models have a handle on Sunday, the GFS does a big shift northward!

MO warnings seem very conservative compared to the amounts project by the main models. Even though the models can overdo it a bit. Perhaps that's just because of uncertainty.

[captaincroc]

27 minutes ago, West is Best said:

I have to say, that I think this is the form horse. It depends how quickly and deeply the arctic air entrenches. But this doesn't look to me like an east-west trajectory at all. I wouldn't be all that surprised if only Devon and Cornwall see the precipitation to be frank. It has happened before. Infamously, if I recall, on 5th-6th February 2009 when right up to the last minute the MetO and all models were predicting the incoming low to sweep across southern Britain and the Midlands. In fact, only Devon and Cornwall copped it:

https://www.theguardian.com/uk/2009/feb/06/cars-stranded-devon-snow

I was fortunate enough to be there at the time and it was magnifique  Here you go with the charts. Look at all familiar?

 

I've been thinking about this this week... The models are updated regularly and you would hope that in that time they are forever correcting it's errors - like sliders being programmed further and further south - if it does cross through the midlands then this is where the mean path has always been. If it does end up Devon etc then the models definitely need a tweak to be so wrong at such a relatively short period of 'modelling' time.

[*Stormforce~beka*]

How often does the temps on XCWeather update?