Model output discussion - summer rolls on

[Man With Beard]

This may seem a bit knee jerk but I'm sensing, bit by bit, a move from a pattern that allows for long settled periods, to a pattern that only allows shorter ones. Next Wednesday may well be the end of the long, unbroken days on end of 30 degree heat? Most runs just seem more and more westerly after this time, and though I never buy Atlantic height rises in advance unless they are anomolously strong, heights do seem to want to hit the Atlantic rather than the UK. 

But then again maybe it'll just be a period of a few days. And of course the models were gunning for an unsettled spell mid July at one point, which completely did not happen. So perhaps early to be looking down this road. But if someone begged me for a forecast D7-D14, that's what I would say. 

Until then, the question is just how much heat we can get out of the present pattern! Still looking like the very hottest air will stay south, but we're still 24 hours away from being sure. Still time to dig that low further south before Tuesday, which could just nudge that record breaking plume of air that 200 miles further north - that's all - to transform the temps from low 90s to the high 90s.

[Frosty.]

I mentioned about the 6z mean earlier and the same applies to the GEFS 12z mean which indicates a change to more average conditions next week with a broadly westerly upper flow, something of a typical n / s split developing with the north / northwest generally more unsettled and coolest, the south not doing too badly with some weak ridging at times but temperatures well down compared to the expected heat across the s / se during the coming days.

 

Edited August 1, 2018 by Frosty.

[Mike Poole]

We'll look guys, sometimes we can predict the weather using the model output some 8 days ahead.  Now is not one of those situations.  Here at T144 the ECM, GFS and FV3 (GFS parallel):

Really significant uncertainty, considering the background signals and long range seasonal model output, I'd put these in order of likelihood as FV3 then ECM then GFS. Either way there's an unsettled spell in there. Certainly keeping the interest going!  We'll see.

Edit ECM down the toilet at T192, but the uncertainties that need resolving are way before this point.  (couldn't find a toilet emoji so I've gone once removed). Chart:

Edited August 1, 2018 by Mike Poole

[Captain Shortwave]

   

Well that is a close call for the heat, that is a very thundery day 7 chart with low pressure developing over France and moving straight north (The 18C isotherm is over the south east so the chance of some nasty storms developing and spreading up from France as well).

Only the GFS shows that deep and rather organised trough moving through with the others developing a weak system which moves through slower, given the breakthrough is at day 7 there is the chance of that low becoming slower still and possibly sinking west of the UK as warm air from the Atlantic ridge and the ridge to our east which weakens this further and the jetstream simply rides over the top. The ECM does slowly clear the low eastwards but all that seems to follow is a rise in pressure from the west with tropical mairitime air moving in so temperatures still look reasonable compared to average.

Edited August 1, 2018 by Captain Shortwave

[blizzard81]

4 minutes ago, Mike Poole said:

We'll look guys, sometimes we can predict the weather using the model output some 8 days ahead.  Now is not one of those situations.  Here at T144 the ECM, GFS and FV3 (GFS parallel):

Really significant uncertainty, considering the background signals and long range seasonal model output, I'd put these in order of likelihood as FV3 then ECM then GFS. Either way there's an unsettled spell in there. Certainly keeping the interest going!  We'll see.

Mmm, one could also say they are quite similar. For example, for each of those charts, my eyes are always looking north west. Very hard to argue against a cooler, less settled theme from next Thursday for at least a couple of days. From where we go from there depends on the strength of any azores ridging. 

[Man With Beard]

13 minutes ago, Captain Shortwave said:

   

Well that is a close call for the heat, that is a very thundery day 7 chart with low pressure developing over France and moving straight north (The 18C isotherm is over the south east so the chance of some nasty storms developing and spread up from France as well), that trough could very well become cut off close to the UK.

Actually 19C if you look at the UK chart! Would be serious thundery potential you'd think. Just over the channel, the heat is extreme. 

[Frosty.]

A thundery low / trough next wednesday on the Ecm 12z marks the hot and humid climax to the upcoming very warm / hot largely settled spell across the south, then cooler and fresher from next thursday with a westerly air flow following briefly but some weather fireworks to come according to this run...and then T+240 sees the next very warm spell building..phew, a lot going on isn't there!

Edited August 1, 2018 by Frosty.

[Captain Shortwave]

2 minutes ago, Man With Beard said:

Actually 19C if you look at the UK chart! Would be serious thundery potential you'd think. Just over the channel, the heat is extreme. 

It is certainly something this summer has lacked (Though I can't complain as there have been thunderstorms here 3 days out of the last 6), you would think some real humdingers could be spawned.

That trough crawls eastwards as move through the first half of week 2, I must admit the Euros are at a point at day 6 where it would take only a small shift south and west on the position of that trough and the result would be that the low would probably not even touch the UK and sink harmlessly towards our south west. It is at that timeframe where you could see that change happen. No inclined to make a call on the longer range just yet, I don't want to get burnt by this (Literally if the westerly solution is wrong with the depth of heat to our south).

[Singularity]

What's happened with all but UKMO this evening, is an adjustment west of the trough far enough to send more of a plunge of cooler air down west of the mega-plume across Europe, but not far enough to counterbalance the resultant unstable environment between the two airmasses by keeping the upper level westerlies too far away for sufficient interaction to take place.

I'll be the first to admit that I've not a clue whether adjustments will continue far enough to keep the instability in check and set up a longer draw of continental heat - this level of detail isn't what the GSDM is about. Certainly is the potential there, though.

Of greater likelihood is that the models are still making too much of the MJO-related forcing going forward from that point (Tue/Wed next week), as we keep seeing a more Nina-like inflation of the Azores High out to our west/southwest and quite flat westerly flow across the UK. While the latter is a feasible result from a thundery low lifting out N or NE, the Nino background favours a new trough to take shape in the mid-Atlantic, boosting the Azores High back northeast toward Scandinavia and putting a quick end to any flat pattern across the UK.

I say favours, as it can never be guaranteed, but to me, it would seem like hard luck for us if a flat and changeable westerly setup persisted for more than a couple of days.

[Man With Beard]

Looking at individual ECM ensembles for Wednesday - massive split. About 30% of runs are hotter than the op run, including the control run which holds the front further west, allowing the extreme heat to reach the UK (high 90s likely). Others see the heat long gone. 

note - even though the op run has one of the highest values for uppers on the ensembles for London, it is slightly 'cooler' at the surface because of a front over the SE

Edited August 1, 2018 by Man With Beard

[Frosty.]

Looking at tonight's Ecm 12z ensemble mean, next week gradually becomes cooler and more changeable from the atlantic following a hot start to next week further southeast but this change to a cooler westerly may prove short-lived with the azores high / ridge possibly building in again as we head towards mid august.

Edited August 1, 2018 by Frosty.

[summer blizzard]

 

1 hour ago, Singularity said:

What's happened with all but UKMO this evening, is an adjustment west of the trough far enough to send more of a plunge of cooler air down west of the mega-plume across Europe, but not far enough to counterbalance the resultant unstable environment between the two airmasses by keeping the upper level westerlies too far away for sufficient interaction to take place.

I'll be the first to admit that I've not a clue whether adjustments will continue far enough to keep the instability in check and set up a longer draw of continental heat - this level of detail isn't what the GSDM is about. Certainly is the potential there, though.

Of greater likelihood is that the models are still making too much of the MJO-related forcing going forward from that point (Tue/Wed next week), as we keep seeing a more Nina-like inflation of the Azores High out to our west/southwest and quite flat westerly flow across the UK. While the latter is a feasible result from a thundery low lifting out N or NE, the Nino background favours a new trough to take shape in the mid-Atlantic, boosting the Azores High back northeast toward Scandinavia and putting a quick end to any flat pattern across the UK.

I say favours, as it can never be guaranteed, but to me, it would seem like hard luck for us if a flat and changeable westerly setup persisted for more than a couple of days.

The key change that may be responsible in my opinion is the state of the AO. If we look at the NOAA anomoly charts for example we see that actually we do have a west US high and an active southern stream relative to average in the Atlantic and a displaced sub-tropical high. The critical difference from the May-July period however is that instead of a solid +AO we have developed heights over the pole which has pushed the primary trough in the Arctic further south than it would otherwise have been and hence we are seeing more energy downstream and less amplification. 

[Singularity]

7 minutes ago, summer blizzard said:

 

The key change that may be responsible in my opinion is the state of the AO. If we look at the NOAA anomoly charts for example we see that actually we do have a west US high and an active southern stream relative to average in the Atlantic and a displaced sub-tropical high. The critical difference from the May-July period however is that instead of a solid +AO we have developed heights over the pole which has pushed the primary trough in the Arctic further south than it would otherwise have been and hence we are seeing more energy downstream and less amplification. 

Indeed, that’s a substantial change unfolding up there.

The theory I’m working with suggests that the current modelling is placing the resultant south-displaced jet stream in the wrong place (i.e. across UK rather than to W/SW) due to mishandling of the balance of MJO v broader-scale tropical forcing.

Whether the theory comes through on this one, is a matter of waiting and seeing... the models have buckled a bit in the medium range today but they’re being particularly stubborn about the longer-term.

[blizzard81]

13 minutes ago, summer blizzard said:

 

The key change that may be responsible in my opinion is the state of the AO. If we look at the NOAA anomoly charts for example we see that actually we do have a west US high and an active southern stream relative to average in the Atlantic and a displaced sub-tropical high. The critical difference from the May-July period however is that instead of a solid +AO we have developed heights over the pole which has pushed the primary trough in the Arctic further south than it would otherwise have been and hence we are seeing more energy downstream and less amplification. 

Indeed, good spot. So many dynamics in play at any given moment. I love extremes in weather but it is essential not to let our preferences blind us to reality. Both the gfs and ecm ensembles point to quite a marked cool down for the UK . They may both be wrong, they could be right. I personally don't care that much now as I am absolutely more than satisfied with what this summer has brought to these shores. It has been magnificent. Remember where we are located on the edge of the northern Atlantic. It really isn't supposed to be this way so I really hope people have made the most of it. 

[summer blizzard]

20 minutes ago, blizzard81 said:

Indeed, good spot. So many dynamics in play at any given moment. I love extremes in weather but it is essential not to let our preferences blind us to reality. Both the gfs and ecm ensembles point to quite a marked cool down for the UK . They may both be wrong, they could be right. I personally don't care that much now as I am absolutely more than satisfied with what this summer has brought to these shores. It has been magnificent. Remember where we are located on the edge of the northern Atlantic. It really isn't supposed to be this way so I really hope people have made the most of it. 

The way i see it the long run modelling from that position gives us two options..

1) The heights over pole will relax allowing for the Aleutian Trough to lift north with a corresponding amplification over the eastern US and the Atlantic High backing north west to allow an Azores Low/Scandi High type response

or 

2) The heights over the pole enhance and force that trough further south east into western Canada with the end result being a stronger Jet Stream downwind. 

..

At this point i think the Tropics have done all they can for now and it's the Arctic profile that matters. Though a good question is why we are seeing increased heights in the Arctic after a solid +AO season.  

[northwestsnow]

Very progressive UKMO this morning.

Still another 5 or 6 days of lovely weather but momentum seems to be building for a more southerly tracking jet.

Still, no complaints from me, after a beautiful may june july and 1st week of August, im kind of looking towards Autumn now.. hoping my strange obsession with a cold foggy November comes off to cap a brilliant year.

Edited August 2, 2018 by northwestsnow

[mb018538]

2 hours ago, northwestsnow said:

Very progressive UKMO this morning.

Still another 5 or 6 days of lovely weather but momentum seems to be building for a more southerly tracking jet.

Still, no complaints from me, after a beautiful may june july and 1st week of August, im kind of looking towards Autumn now.. hoping my strange obsession with a cold foggy November comes off to cap a brilliant year.

I don't see that at all...all the models bring the low into play in a weeks time, but the ECM and GFS move it away into scandi fairly quickly, with the Azores high never too far away afterwards.



At day 9 we're still on the warmer side of the jet, which is weak anyway.

[Snowyowl9]

Havn`t seen this lately,summer is slipping south.

[northwestsnow]

6 minutes ago, mb018538 said:

I don't see that at all...all the models bring the low into play in a weeks time, but the ECM and GFS move it away into scandi fairly quickly, with the Azores high never too far away afterwards.



At day 9 we're still on the warmer side of the jet, which is weak anyway.

Yes E C does push the jet back whence it came by day 10 . Will be interesting to see the next few runs.

[danm]

4 minutes ago, Snowyowl9 said:

Havn`t seen this lately,summer is slipping south.

Did we not see very similar weather last weekend? 

We still have just under a 1/3rd of summer to go. 

Edited August 2, 2018 by danm

[Coopsy]

3 hours ago, northwestsnow said:

Very progressive UKMO this morning.

Still another 5 or 6 days of lovely weather but momentum seems to be building for a more southerly tracking jet.

Still, no complaints from me, after a beautiful may june july and 1st week of August, im kind of looking towards Autumn now.. hoping my strange obsession with a cold foggy November comes off to cap a brilliant year.

It's not a strange obsession - there's nothing better than those cold foggy November days.

I think they'll be a blip again after 5/6 days then a cooler, still warm, settled period, then a blip and so the cycle continues until the snowdrifts come in December

[Methuselah]

48 minutes ago, danm said:

Did we not see very similar weather last weekend? 

We still have just under a 1/3rd of summer to go. 

And, to me at least, it looks primed for a renewed build of high pressure?

[mushymanrob]

36 minutes ago, Ed Stone said:

And, to me at least, it looks primed for a renewed build of high pressure?

it does, but sadly no other model suite suggests this. all indications are pointing towards troughing establishing as the main driver after the current warm spell departs next week.

[Man With Beard]

Strong agreement on the clusters now for a trough to affect the UK by next Wednesday - but question marks over the angle and speed of approach, which may affect whether or not we get one more very hot day

By D10, extremely good agreement on heights centered more to the west, so a cooler air stream than we've been used to, low 20s perhaps the new norm

But the extended ensembles cast doubt on how long for - by D14, plenty of hotter options again as heights cross to the south and east on some clusters, but rather uncertain by this stage with less settled possibilities 

[Frosty.]

The Ecm 00z ensemble mean shows there is strong support for a change to cooler cyclonic conditions next week with a north atlantic air mass bringing temperatures down to average or lower, especially further n / nw.

Edited August 2, 2018 by Frosty.