Model Output Discussion - Colder but how cold and for how long?

[Rob 79812010]

9 minutes ago, Rob 79812010 said:

Does this happen when there's a slight switch to North westerly??

I ask because manc got 3 inches that day. Usually we get from north westerly flows

[Midlands Ice Age]

1 hour ago, Derecho said:

Without working on the ECM, GFS or UKMO models, I don't know how you can prove this without any evidence?

If you were just letting Machine learning algorithms take over the models without an understanding of how the output is created, then yes I'd agree... but every piece of software is different.

Derecho...

30 years of modelling, programming , analysis, technology design and implementation has left its scars on me. 

Twenty years ago we needed more machine power.

Now, unless we sort out the assumptions  and get them analysed correctly into mathematics  we will only magnify the errors as we push ever deeper into being able to look at ever more local detail.

Tamara is showing where some of the current assumptions are wrong, or at least give a totally different view. .

People on here showed how the stratosphere could affect things greatly. (10 years ago) This was incorporated into the models (though I believe is now possibly over responsive (see below)).

The only people to gain by increasing the computing power right now are 1) computer salesmen, and 2) system design specialists who have no further ideas as to how to improve the current models.

Incorrect assumptions ALWAYS increase volatility in output. Increased  computing power will only serve to show up any design errors.

I appreciate that increasing the spread by the changing the input criteria, is one method of reducing any errors. But the initial 'errors' are still present, and will only serve to produce more chaos.

I am talking about from where the models are standing today (which is much better than they were 5-10 years ago).  Spending hundreds of millions on more computing power right now will not give the same rewards as ensuring some of the 'unknowns' are fully researched and included  as regards the accuracy of the models..

1)     Extra notes.... Take today and this graphic taken from the above (to be saved)....

  

The whole of even  the western hemisphere has been impacted by the the slope and shape of the high forecast to develop  over  the Bering Ocean.  Changing its inclination or intensity will dramatically change the forecast for the whole Northern Hemisphere via mechanisms previously discussed on here. Both the ECM and GFS have shown this happening over the last week. Both had to withdraw from their positions . Something is not 'spot on'.

Will they this time? Can you tell me? I assume that this situations has come about as to their incorrectly handling the totality of the 'telecomms' signals. 

2) As to whether the models are accurate from a scientific pov.    I cannot make any comments  (you are correct).  However they have now released documentation on the 'CC' models, which were based upon forecast models  (I  am told),  and for the previous release of them there were still around 25 assumptions which were not yet proven. If they were missing in the 'CC' models then I assume they were not in the forecast models.  - In the CC models they substituted parameters. 

Sorry to mention the XX word banned on here  - MODS.

So IMO opinion,   (FWIW)  there is still quite a way to go before we can say that all the assumptions (and therefore the absolutely correct science) built into the models, means that models are correct.

Until that happens  putting in more computing power will increase chaos (not decrease). that is what my 30 odd years of experience has taught me.

MIA

Edited January 12 by Midlands Ice Age

[Downburst]

Week after next surface pressure anomalies (for the entire weekly mean)

x

It's followed by a resurgence of high pressure, with the following week showing that possibly moving north west, I think dry and hopefully sunny for the time of year looking at precipitation anomaly.

However, next week is the one chance I'd suspect of proper cold this January, with it gradually warming up. I think we may well have a dry spell end Jan well into February.

 

To add a rare at this time of frantic posts I put in December 19, to show the usefulness of these charts as a guide for probabilities

Edited January 12 by Downburst

[bluearmy]

the day 15 eps mean and spreads scream Greenland tpv very loudly and upper ridge into Iberia 

= flat zonal 

now the extended ens have been promising a return to a ne Canadian vortex for some time - it’s taken longer to get there than first modelled but it’s now looking v likely indeed

the only caveat I have is that the trop continues to lead the dance and we know how unpredictable trop modelling is as week 2 progresses. there may be feedback issues that are consolidating a strengthening which may not verify in that fashion.  Having said that, it was noted about a week ago that the modelling wanted to stretch the spv from Barents to e Canada, split it, then return the Canadian segment back to svaalbard. We know from experience that this east - west - east movement of a coupled  spv/tpv will usually fire up the northern arm.  It looks like the split that enables the n Atlantic height rise will also be responsible for the fired up jet as the two segments are rejoined on our side of the NH.  in addition, the split Canadian segment dropping into n America doesn’t help as it increases the temp differential which leads to an even stronger jet. and the displaced nature of the spv our side means that this movement is at a southerly latitude which means the jet is aimed at us.  

as nick alluded earlier, there are sniffs of disruption which could force that jet into Iberia but that’s not what the nwp is showing 

I do have nagging doubts on this but it’s rare that the modelling for week 2 is wrong when there is so much agreement across the nwp  

there currently aren’t enough rogue ens members to justify any doubts  (actually the 06z gefs have a few so maybe need to see what happens on the 12z eps) 

Edited January 12 by bluearmy

[Bricriu]

23 minutes ago, Downburst said:

Week after next surface pressure anomalies (for the entire weekly mean)

x

It's followed by a resurgence of high pressure, with the following week showing that possibly moving north west, I think dry and hopefully sunny for the time of year looking at precipitation anomaly.

However, next week is the one chance I'd suspect of proper cold this January, with it gradually warming up. I think we may well have a dry spell end Jan well into February.

 

To add a rare at this time of frantic posts I put in December 19, to show the usefulness of these charts as a guide for probabilities

It's disappointing  in one way that much of February would potentially be eaten up with predominantly  dry weather,  but at the same  time it's preferable  to the GFS horror show which would could  lead to at least 7 - 10 days of zonal  weather if not more. One further thing I will  say is even  with a grim nh profile things can change for the better in the space of a few days- you only have to  look at the charts prior  to some noteworthy cold spell as evidence of that  .

Edited January 12 by Bricriu

[offerman]

24 minutes ago, Midlands Ice Age said:

Derecho...

30 years of modelling, programming , analysis, technology design and implementation has left its scars on me. 

Twenty years ago we needed more machine power.

Now, unless we sort out the assumptions  and get them analysed correctly into mathematics  we will only magnify the errors as we push ever deeper into being able to look at ever more local detail.

Tamara is showing where some of the current assumptions are wrong, or at least give a totally different view. .

People on here showed how the stratosphere could affect things greatly. (10 years ago) This was incorporated into the models (though I believe is now possibly over responsive (see below)).

The only people to gain by increasing the computing power right now are 1) computer salesmen, and 2) system design specialists who have no further ideas as to how to improve the current models.

Incorrect assumptions ALWAYS increase volatility in output. Increased  computing power will only serve to show up any design errors.

I appreciate that increasing the spread by the changing the input criteria, is one method of reducing any errors. But the initial 'errors' are still present, and will only serve to produce more chaos.

I am talking about from where the models are standing today (which is much better than they were 5-10 years ago).  Spending hundreds of millions on more computing power right now will not give the same rewards as ensuring some of the 'unknowns' are fully researched and included  as regards the accuracy of the models..

1)     Extra notes.... Take today and this graphic taken from the above (to be saved)....

  

The whole of even  the western hemisphere has been impacted by the the slope and shape of the high forecast to develop  over  the Bering Ocean.  Changing its inclination or intensity will dramatically change the forecast for the whole Northern Hemisphere via mechanisms previously discussed on here. Both the ECM and GFS have shown this happening over the last week. Both had to withdraw from their positions . Something is not 'spot on'.

Will they this time? Can you tell me? I assume that this situations has come about as to their incorrectly handling the totality of the 'telecomms' signals. 

2) As to whether the models are accurate from a scientific pov.    I cannot make any comments  (you are correct).  However they have now released documentation on the 'CC' models, which were based upon forecast models  (I  am told),  and for the previous release of them there were still around 25 assumptions which were not yet proven. If they were missing in the 'CC' models then I assume they were not in the forecast models.  - In the CC models they substituted parameters. 

Sorry to mention the XX word banned on here  - MODS.

So IMO opinion,   (FWIW)  there is still quite a way to go before we can say that all the assumptions (and therefore the absolutely correct science) built into the models, means that models are correct.

Until that happens  putting in more computing power will increase chaos (not decrease). that is what my 30 odd years of experience has taught me.

MIA

Fantastic post highlighting improvements that can be made with modelling charts. Absolute pleasure reading your posts backed up by all that experience.  Thank you for your input

[Severe Siberian icy blast]

2 hours ago, MJB said:

Frontal snow ..............................yeah

 

If that stalls a bit, might get a covering before it goes wet 

But are you even taking the time to talk about a chart so far away?! 

Surely the focus has to be on the reliable and looking for hints of change or not in the early stages. 

Posting a ppn chart 9 days away is as much use as trying to cook without a cooker. 

[offerman]

1 minute ago, Severe Siberian icy blast said:

But are you even taking the time to talk about a chart so far away?! 

Surely the focus has to be on the reliable and looking for hints of change or not in the early stages. 

Posting a ppn chart 9 days away is as much use as trying to cook without a cooker. 

Excellent post it seems this happens far too. Often the charts are just so unreliable that far out. Can’t even be an indication as they are so topsy-turvy even in shorter time frames of 5 to 6 days can be so inconsistent, let alone nine days or above completely agree with you.

[Derecho]

33 minutes ago, Midlands Ice Age said:

Derecho...

30 years of modelling, programming , analysis, technology design and implementation has left its scars on me. 

Twenty years ago we needed more machine power.

Now, unless we sort out the assumptions  and get them analysed correctly into mathematics  we will only magnify the errors as we push ever deeper into being able to look at ever more local detail.

Tamara is showing where some of the current assumptions are wrong, or at least give a totally different view. .

People on here showed how the stratosphere could affect things greatly. (10 years ago) This was incorporated into the models (though I believe is now possibly over responsive (see below)).

The only people to gain by increasing the computing power right now are 1) computer salesmen, and 2) system design specialists who have no further ideas as to how to improve the current models.

Incorrect assumptions ALWAYS increase volatility in output. Increased  computing power will only serve to show up any design errors.

I appreciate that increasing the spread by the changing the input criteria, is one method of reducing any errors. But the initial 'errors' are still present, and will only serve to produce more chaos.

I am talking about from where the models are standing today (which is much better than they were 5-10 years ago).  Spending hundreds of millions on more computing power right now will not give the same rewards as ensuring some of the 'unknowns' are fully researched and included  as regards the accuracy of the models..

1)     Extra notes.... Take today and this graphic taken from the above (to be saved)....

  

The whole of even  the western hemisphere has been impacted by the the slope and shape of the high forecast to develop  over  the Bering Ocean.  Changing its inclination or intensity will dramatically change the forecast for the whole Northern Hemisphere via mechanisms previously discussed on here. Both the ECM and GFS have shown this happening over the last week. Both had to withdraw from their positions . Something is not 'spot on'.

Will they this time? Can you tell me? I assume that this situations has come about as to their incorrectly handling the totality of the 'telecomms' signals. 

2) As to whether the models are accurate from a scientific pov.    I cannot make any comments  (you are correct).  However they have now released documentation on the 'CC' models, which were based upon forecast models  (I  am told),  and for the previous release of them there were still around 25 assumptions which were not yet proven. If they were missing in the 'CC' models then I assume they were not in the forecast models.  - In the CC models they substituted parameters. 

Sorry to mention the XX word banned on here  - MODS.

So IMO opinion,   (FWIW)  there is still quite a way to go before we can say that all the assumptions (and therefore the absolutely correct science) built into the models, means that models are correct.

Until that happens  putting in more computing power will increase chaos (not decrease). that is what my 30 odd years of experience has taught me.

MIA

Ah yes if you are saying the assumptions on the model are wrong then I agree with you, there are assumptions after all... based on the knowledge we have. If assumptions were completely correct, we'd have a much better handle on things like turbulence. I wouldn't want to see the correct mathematical equations for that.

Though the models will get better if there is more data available to put in them, especially if coverage is improved. However there will be a glass ceiling due to uncertainties over assumptions. Modelling atmospheric circulation is exceptionally difficult and is pretty much why in a warming climate we still have uncertainties regionally.

Apologies, I probably misinterpreted your comments on software... 

Can't give a more detailed response right now but it's probably worth discussing in another thread.

[Battleground Snow]

Hello high amplitude,

It's slowing down a little bit getting there though, so maybe 25-30th of January will be zonal........

Cold zonality with wedges

[Gowon]

28 minutes ago, bluearmy said:

the day 15 eps mean and spreads scream Greenland tpv very loudly and upper ridge into Iberia 

= flat zonal 

now the extended ens have been promising a return to a ne Canadian vortex for some time - it’s taken longer to get there than first modelled but it’s now looking v likely indeed

the only caveat I have is that the trop continues to lead the dance and we know how unpredictable trop modelling is as week 2 progresses. there may be feedback issues that are consolidating a strengthening which may not verify in that fashion.  Having said that, it was noted about a week ago that the modelling wanted to stretch the spv from Barents to e Canada, split it, then return the Canadian segment back to svaalbard. We know from experience that this east - west - east movement of a coupled  spv/tpv will usually fire up the northern arm.  It looks like the split that enables the n Atlantic height rise will also be responsible for the fired up jet as the two segments are rejoined on our side of the NH.  in addition, the split Canadian segment dropping into n America doesn’t help as it increases the temp differential which leads to an even stronger jet. and the displaced nature of the spv our side means that this movement is at a southerly latitude which means the jet is aimed at us.  

as nick alluded earlier, there are sniffs of disruption which could force that jet into Iberia but that’s not what the nwp is showing 

I do have nagging doubts on this but it’s rare that the modelling for week 2 is wrong when there is so much agreement across the nwp  

there currently aren’t enough rogue ens members to justify any doubts  (actually the 06z gefs have a few so maybe need to see what happens on the 12z eps) 

 Is it the disruption of the jet that get us to that first week of Feb anomaly chart?

[sheikhy]

Ecm lookin better at 66 hours on the 06z!!stronger high aswell south of greenland!

[February1978]

41 minutes ago, Midlands Ice Age said:

Derecho...

30 years of modelling, programming , analysis, technology design and implementation has left its scars on me. 

Twenty years ago we needed more machine power.

Now, unless we sort out the assumptions  and get them analysed correctly into mathematics  we will only magnify the errors as we push ever deeper into being able to look at ever more local detail.

Tamara is showing where some of the current assumptions are wrong, or at least give a totally different view. .

People on here showed how the stratosphere could affect things greatly. (10 years ago) This was incorporated into the models (though I believe is now possibly over responsive (see below)).

The only people to gain by increasing the computing power right now are 1) computer salesmen, and 2) system design specialists who have no further ideas as to how to improve the current models.

Incorrect assumptions ALWAYS increase volatility in output. Increased  computing power will only serve to show up any design errors.

I appreciate that increasing the spread by the changing the input criteria, is one method of reducing any errors. But the initial 'errors' are still present, and will only serve to produce more chaos.

I am talking about from where the models are standing today (which is much better than they were 5-10 years ago).  Spending hundreds of millions on more computing power right now will not give the same rewards as ensuring some of the 'unknowns' are fully researched and included  as regards the accuracy of the models..

1)     Extra notes.... Take today and this graphic taken from the above (to be saved)....

  

The whole of even  the western hemisphere has been impacted by the the slope and shape of the high forecast to develop  over  the Bering Ocean.  Changing its inclination or intensity will dramatically change the forecast for the whole Northern Hemisphere via mechanisms previously discussed on here. Both the ECM and GFS have shown this happening over the last week. Both had to withdraw from their positions . Something is not 'spot on'.

Will they this time? Can you tell me? I assume that this situations has come about as to their incorrectly handling the totality of the 'telecomms' signals. 

2) As to whether the models are accurate from a scientific pov.    I cannot make any comments  (you are correct).  However they have now released documentation on the 'CC' models, which were based upon forecast models  (I  am told),  and for the previous release of them there were still around 25 assumptions which were not yet proven. If they were missing in the 'CC' models then I assume they were not in the forecast models.  - In the CC models they substituted parameters. 

Sorry to mention the XX word banned on here  - MODS.

So IMO opinion,   (FWIW)  there is still quite a way to go before we can say that all the assumptions (and therefore the absolutely correct science) built into the models, means that models are correct.

Until that happens  putting in more computing power will increase chaos (not decrease). that is what my 30 odd years of experience has taught me.

MIA

As someone also in a similar scientific software business, I agree with the sentiment of this.

Initial conditions are a big thing in my opinion. In an inherently chaotic system, if you don't get the initial state correct you won't get an accurate answer. Rubbish in ---> rubbish out. 

Areas lacking data are at altitude, over the oceans and near the poles where there are no humans to record and report data, so satellite and aircraft data are used I believe.

Then you have the solution method which always has a truncation error and probably has efficiencies to make sure it is a) robust and b) quick enough to reach a solution. Developers make compromises/assumptions which always have impacts in due course. For example, mountainous areas will be a problem - how do you model the boundaries there? You can't directly model each feature (mountain), it's too small a part of the domain, but they are important for (eg) torque as discussed at length by others previously – how do we know we are accurate enough?

All numerical models have inherent assumptions and weaknesses, much of the skill of those using them is to understand where those limitations are. It has been really fascinating to see the experts here comment on the output, what they trust and what they don't. We're in one of those spells where they are not convinced by the outputs they are seeing and giving their opinions, much respect for them sharing their knowledge from me – thanks!

Apologies if this is slightly off piste, but it is relatively quiet….

[sheikhy]

Very good and an upgrade at 72 hours!colder air further south and west and light blues near south east greenland not as apparent!!!

[Methuselah]

20 minutes ago, offerman said:

Fantastic post highlighting improvements that can be made with modelling charts. Absolute pleasure reading your posts backed up by all that experience.  Thank you for your input

I'm surprised no-one has mentioned chaos theory -- even some of the most basic deterministic equations behave chaotically when iterated many times. And, then, there's the inherent complexity to think about? 

[Mark wheeler]

A nice 6z Jma run with some snow around .

[Mcconnor8]

11 minutes ago, Mark wheeler said:

A nice 6z Jma run with some snow around .

ECM 06z has a slightly more direct Northerly than the 0z with a better block into Greenland, a move towards UKMO/ICON early on it looks like.

If we see these trends continue on the 12z suites could be a decent set of upgrades on the 0z runs, and if they do means a very high chance that the low does end up moving through France.

Edited January 12 by Mcconnor8

[jacke]

1 hour ago, Catacol said:

Yeah - charts like this come thick and fast in most UK winters.

 

 

1 hour ago, Catacol said:

Yeah - charts like this come thick and fast in most UK winters.

 

 

Well said Catacol! But Congratulations to DIS1970. You will be my first ignore! You must have been very eager to make a comment. Sad that it was so pointless without any justification.  Not seen as much divergence in recent years at such short timescales.  Records will show that any real cold is rare beyond 7 days. However, not unknown and the large scale differences showing beyond next Friday, albeit more showing a relative cold breakdown just confirms what the the more knowledgeable are saying, Be patient and don’t get hung up in what is far FI  in these scenarios. 

[TSNWK]

7 minutes ago, Mcconnor8 said:

ECM 06z has a slightly more direct Northerly than the 0z with a better block into Greenland, a move towards UKMO/ICON early on it looks like.

If we see these trends continue on the 12z suites could be a decent set of upgrades on the 0z runs.

hope so - we now need to keep these near term upgrade as best we can, squeeze as much we can next week - the holistic view in the northern hem' is now setting up for the vortex to  ramp up to our north west from next week and we go back to chasing topplers and ridges in the zonal flow for a couple of weeks afterwards at least

[MJB]

36 minutes ago, Severe Siberian icy blast said:

But are you even taking the time to talk about a chart so far away?! 

Surely the focus has to be on the reliable and looking for hints of change or not in the early stages. 

Posting a ppn chart 9 days away is as much use as trying to cook without a cooker. 

Oh dear - not this old chestnut again, its the Model discussion thread, not the pre 120h thread.

It's also a good way of looking for trends. I can't see you commenting against charts that are even further a field. ODD 

Then use a BBQ

Edited January 12 by MJB

[Mcconnor8]

3 minutes ago, TSNWK said:

hope so - we now need to keep these near term upgrade as best we can, squeeze as much we can next week - the holistic view in the northern hem' is now setting up for the vortex to  ramp up to our north west from next week and we go back to chasing topplers and ridges in the zonal flow for a couple of weeks afterwards at least

I know it looks like that with the ensemble packs at the moment, but keeping in mind what Tamara said I think there is plenty of scope for that to change in the next few days, the models are really struggling with 4-5 days out right now so I would put much less faith in the longer term output at the moment.

Edited January 12 by Mcconnor8

[Catacol]

1 hour ago, mountain shadow said:

No one is arguing that synoptically things looks great with rare Arctic air making an appearance and bitter cold is a certainty.

What is currently frustrating is the lack of snow falling for 75% of the population. 

Things could change of course.

Sorry MS - I've got to come back on this. The chart I posted has a moisture-laden (given its origins) system in the bay of biscay approaching on a ENE vector and a cold to very cold (-8 850s over most of the UK) trough in place that has come from Scandy to the NE. If anyone on here is frustrated at this 120h context then either they grew up in Finland, haven't been on this forum long enough to understand the usual bounds of our winter weather or are just not interpreting the pattern effectively. Maybe a combination of all 3.

Deep breath. These synoptics are rare. There is no way we can have a handle on precipitation amounts at this range. If a system was forecast to hit direct from the W or SW then it becomes a snow to rain event....so we NEED it to deflect and run to the south even though it narrows the band of snowfall and involves fewer people. We would love a strong flow off the north sea for streamers, but again there is no way at this range that we can be sure quite what will occur there, and in that NE flow it is quite possible for features to become embedded that - once again - we have no chance of spotting at 120h.

If what is on offer next week is not good enough then it virtually never will be. The 7 Feb 1991 style of synoptic is SO rare that, at the age of 53, I reckon I've seen no more than half a dozen of those in my lifetime and in the last 27 years only two - 2010 and 2018. Before that 1996 which locally around me was spectacular. Do we really need to go down the track of waiting for events that happen twice in 27 years to start feeling good about them?

The answer has to be no. Next week is looking great. Is it looking 1991 great? No. But great nonetheless and some are going to end up very happy indeed. And bear in mind that this is just the start of a drawn out spell of cool/cold/very cold weather which I am pretty certain is going to feature more than a single bite at the cherry. The 1991 redux isn't off the table.

Rant over. I hope the majority of folk on here are enjoying what is unfurling. Short range surprises will happen, next week will be properly cold and the long term prognosis is good. The models today are suddenly seeing ridges popping up in a flow that was modelled pretty flat into week 2 yesterday. Watch that trend develop. The only thing frustrating me at the moment is the wait for the MJO to get through the maritimes and for frictional torque to start climbing again. As of 9th Jan still waiting...should be soon now. But otherwise - all good!!!

[tight isobar]

Definitive slight upgrade via 6z ec a better aligned inflow- and we watch to the west as the much spoken above system sets sail to nw Europe- but we await as per dynamics!

Edited January 12 by tight isobar

[Tamara]

The extended period continues to look very problematic in respect of NWP to me.

The MJO passing through the Indian Ocean has bumped up easterly inertia/trade winds and creating problems in the modelling with Pacific ridging and with the models gunning for booting up the polar jet downstream as a consequence. This at the same time providing insight into the modelling of the lobes of the polar vortex and the spectre of them fusing together.

However, westerly wind inertia remains above average across the extra tropics and this presents a question mark about the Pacific amplification and downstream polar jet being over modelled. But most especially based on the passage of tropical convection quickly set to navigate through Phases 4 & 5 imminently during the period in question when the northern arm is being programmed to flatten the pattern. As the MJO hits the borders of Phase 5 the next starting pistol is renewed to ladder up angular momentum tendency. Putting all this together,  a very squeezed timeframe for this sequence of polar jet modelling is only available in my book to complete, let alone sustain itself if it does.

The suspicion I continue to have is that these poleward eddies that the models propose to increase polar jet momentum, will get sheared off and this whilst this still leaves a flat jet stream coming from upstream, the shearing off process will cut off the supply to the polar jet in mid stream and force it to backtrack into the sub tropical jet. Much the theme of discussion of late. 

That process, leaving some of the residual ridging between Greenland & Iceland intact and/or re-programming re-emergence of wedge type ridging and subsequent disruption of Canadian lobe energy in mid Atlantic. This leaves southerly jet kayaks to resume progress and changes the extended ensemble means that propose a flat westerly pattern across NW Europe & inflating Azores High.

It will be very interesting (as I see it) to watch and monitor if this does actually transpire.

Edited January 12 by Tamara

[Speedbird]

17 minutes ago, Mcconnor8 said:

ECM 06z has a slightly more direct Northerly than the 0z with a better block into Greenland, a move towards UKMO/ICON early on it looks like.

If we see these trends continue on the 12z suites could be a decent set of upgrades on the 0z runs, and if they do means a very high chance that the low does end up moving through France.

barely a glancing blow on those frames, the northerly fast becoming a NW'ly barely affecting anywhere south of the Midlands