Model output discussion 14/04/18

[Tim Bland]

15 minutes ago, mb018538 said:

Fairly big warm outlier (as expected really). Interesting that by 7 4/5 of the 20 members really kill the heat off with a sharp drop in 850 temps. Of course that still leave 15 members at or above the average - still the form horse, and the solution you'd have to favour.

Strong signal for some welcome rain at the end of the week. Probably in the form of Thundery showers?

[Frosty.]

Looking at the GEFS 6z mean there's plenty more of this gorgeous very warm / hot weather to look forward to, not only this week but next week too, especially further south right through to mid July.

[Derecho]

Quite the Northern hemisphere view there from the GFS, it looks as though the polar vortex over the Canadian arctic has persisted into the Summer!

Which encourages high pressure to meander across to us...

[cheese]

1 hour ago, Summer Sun said:

The met office have just gone public stating high pressure will be with us for another TWO WEEKS!!

 

Doesn't look like they think the cold front will make it to the UK on Friday either which is good (though it was only supposed to affect northern Scotland anyway).

[mb018538]

24 minutes ago, Quicksilver1989 said:

Quite the Northern hemisphere view there from the GFS, it looks as though the polar vortex over the Canadian arctic has persisted into the Summer!

Which encourages high pressure to meander across to us...

It's quite unusual to get the polar jet wrapped that tightly around the north pole without and meanders!

 

 

1 hour ago, Tim Bland said:

Strong signal for some welcome rain at the end of the week. Probably in the form of Thundery showers?

Indeed, hence the differing ppn spikes - some non existent, some very big, depending on the ensemble member. The BBC etc aren't forecasting much, so I think you'd be more likely to miss one than catch one at this stage.

[Captain Shortwave]

Pretty good agreement between the models out to the end of the coming weekend.

GFS 06z just to show the afternoon pressure pattern but is pretty much the same as the rest of the morning output.

   

High pressure slap bang over the UK, very light winds and gentle sea breezes around the coasts.

GFS temperatures

   

Very warm for most and hot across central and southern England

 

Another BBQ weekend looks pretty much nailed at the moment, the following week carries more uncertainty in regards to the position of the high, if it can drift east and allow the heat building over Spain to drift northwards then the July record set a couple of years ago could be under serious threat. 

[Man With Beard]

Just a note on the extended. The EC clusters haven't updated for a few days. I have been trying to keep up to date with individual ECM ensembles using weather.us but there's a lot of data to go through!

My sense from the past few ensemble runs is:

- Settled weather likely to last until at least 14th July - probably hot all the way but just the chance of some northerly influence slipping into the pattern. 

- After that (15-17th), a bit of a signal for a mobile period in the north. No clear signal for either a breakdown or continuation of the heatwave in the southern half, with several different ways forward suggested. 

[ancientsolar]

49 minutes ago, Captain Shortwave said:

Pretty good agreement between the models out to the end of the coming weekend.

GFS 06z just to show the afternoon pressure pattern but is pretty much the same as the rest of the morning output.

   

High pressure slap bang over the UK, very light winds and gentle sea breezes around the coasts.

GFS temperatures

   

Very warm for most and hot across central and southern England

 

Another BBQ weekend looks pretty much nailed at the moment, the following week carries more uncertainty in regards to the position of the high, if it can drift east and allow the heat building over Spain to drift northwards then the July record set a couple of years ago could be under serious threat. 

am I reading 32 Celsius at 8pm Sunday in London? 

[Captain Shortwave]

1 minute ago, ancientsolar said:

am I reading 32 Celsius at 8pm Sunday in London? 

It's the maximum temperature between 2pm and 8pm (So that temperatures would be recorded briefly sometime between 3pm and 5pm when the temperatures are usually the highest). The temperatures are even more impressive when you see the 850s which are generally around the 12c mark, very dry and clear underneath the high giving maximum insolation.

I would add that the start of next week probably remains hot and sunny for most (The ECM does bring a front south on Tuesday to cool things down for northern and eastern areas, the GFS does not do this of course).

[ancientsolar]

5 minutes ago, Captain Shortwave said:

It's the maximum temperature between 2pm and 8pm (So that temperatures would be recorded briefly sometime between 3pm and 5pm when the temperatures are usually the highest). The temperatures are even more impressive when you see the 850s which are generally around the 12c mark, very dry and clear underneath the high giving maximum insolation.

I would add that the start of next week probably remains hot and sunny for most (The ECM does bring a front south on Tuesday to cool things down for northern and eastern areas, the GFS does not do this of course).

that makes sense. GFS temp charts on wetterzentrale aren't easy to read, but 32 at 8pm.. was looking very odd.. thermometer on top of someones BBQ 

[Leo97t]

2003 record must be panicking when as it looks at the Gfs 12z

[mb018538]

UKmo 12z tapers the heat somewhat, with 850s only around 6-8c - so more mid twenties and comfortable.

gfs goes mad and turns on the burners, probably somewhere seeing 35c if that comes off! 

[Frosty.]

The Gfs 12z shows a lovely plume next week..phew that would be hot.

[Cheshire Freeze]

9 minutes ago, mb018538 said:

UKmo 12z tapers the heat somewhat, with 850s only around 6-8c - so more mid twenties and comfortable.

gfs goes mad and turns on the burners, probably somewhere seeing 35c if that comes off! 

GFS shows a plume which ultimately spells the end of the heatwave on the 12z run...but it sure does go out in style. 

Think someone mentioned yesterday (possibly Summer Blizzard) that the trough to west, plume scenario usually ushers the Atlantic back in shortly afterwards.

Just one of many scenarios possible going forward.

[Man With Beard]

7 minutes ago, CreweCold said:

GFS shows a plume which ultimately spells the end of the heatwave on the 12z run...but it sure does go out in style. 

Think someone mentioned yesterday (possibly Summer Blizzard) that the trough to west, plume scenario usually ushers the Atlantic back in shortly afterwards.

Just one of many scenarios possible going forward.

Yet another Biscay low scenario, though. Yet more model chaos if it goes down that road. One option being a full on plume, which I suspect would trouble the high 90s if it works out GFS style. 

Edited July 2, 2018 by Man With Beard

[The PIT]

9 minutes ago, CreweCold said:

GFS shows a plume which ultimately spells the end of the heatwave on the 12z run...but it sure does go out in style. 

Think someone mentioned yesterday (possibly Summer Blizzard) that the trough to west, plume scenario usually ushers the Atlantic back in shortly afterwards.

Just one of many scenarios possible going forward.

That's the one where it's showing 33C at midnight. I think it's marbles are a bit wonky that far out. However there is a possibility of some record heat from this. As for plumes alas just mere shadows of what plumes used to be like and nowadays very rarely deliver.

[Frosty.]

Mid 30's celsius potential next week on the Gfs 12z when you consider that it usually undercooks maxima in summer. As most of us know from experience, plumes are usually followed by the atlantic and this run is no exception...I think I would rather see the hot largely settled spell continue until the end of august but at the same time I fully appreciate the water shortages developing, we need rain but I'm loving these hot sunny days!

Edited July 2, 2018 by Frosty.

[Singularity]

I suspect GFS is jumping the gun a bit with the Iberian low deepening so much so soon; other models seem to be voting for such events to be around the midpoint of the month, if occurring at all.

Reason behind this is that as the signal for a temporary retraction of the subtropical ridge takes effect, GFS keeps splitting a secondary ridge away east to allow some Atlantic trough interaction with the Iberian one, but the other models prefer to keep the subtropical ridge whole, with temps actually trending at least slightly for much or all the UK prior to a more east placement resuming and temps heading up again.

That last bit, though, is when northern parts come under threat of a cooler westerly regime, as part of the rising AAM response is a stronger polar jet which could conceivably squeeze the ridge into a flatter shape with the northern edge across Scotland. 

Then again, it could locate north of usual again (N. Atlantic SST pattern impact perhaps?) and bring even more easterlies to the south!

Edited July 2, 2018 by Singularity
SST Note

[Mike Poole]

In the semi-reliable, all models are looking very settled at T144:

i personally think the potential plume idea is a bit premature but it will certainly be worth looking to see to what extent it shows up on the ensembles from now on.

In the mean time, scorchio! 

[Tamara]

3 hours ago, Man With Beard said:

Just a note on the extended. The EC clusters haven't updated for a few days. I have been trying to keep up to date with individual ECM ensembles using weather.us but there's a lot of data to go through!

My sense from the past few ensemble runs is:

- Settled weather likely to last until at least 14th July - probably hot all the way but just the chance of some northerly influence slipping into the pattern. 

- After that (15-17th), a bit of a signal for a mobile period in the north. No clear signal for either a breakdown or continuation of the heatwave in the southern half, with several different ways forward suggested. 

I try no to let preferences influence my thinking in terms of the weather patterns, and attempt to suggest pros and cons for whatever realistic possibilities are ahead. Its not always easy!

But some self indulgence just for once. As far as I am concerned, this summer is proving a perfect tonic with its long sunny days, warmth and, being close to the coast, a lovely breeze to go along with it. It would be a delight for this to continue as long as possible with just a shower every now and then to refresh the garden

Its hard indeed to dispute the longevity of the spell to mid month. The bread and butter EC London ensemble has been on a wonderful auto repeat for many days now and this morning is no exception.

 

The suggestion of the northerly influence, c/o an EC extended signal for a Scandinavian trough which has lurked in the distance and not thus far come forward in time has attempted hints on the last couple of operationals and rather echoes the suggested sentiments of previous posts where seasonal wavelengths in tandem with a low angular momentum regime would retrogress the pattern.

However while we have seen the familiar dominant Atlantic ridge that is typical of this sort of regime, the longwave pattern has been (happily) stuck with the downstream trough response well out of the way over NW Russia and no retrogression in real time. In fact there have been repeated corrections if anything eastwards with cool air advection southwards last week proving too progressive as suggested might happen in a last post. with that Iberian High in situ helping keeping the warmth in place

With this in mind its worth repeating again the limitations that NWP has in terms of its systemic biases and difficulties modelling tropical convection and momentum processes, often missing more micro scale flare-ups (such as recently and on-going in the Pacific) which mean that the cyclical MJO accounts for a surprisingly smaller amount of the tropical forcing budget that influences the atmospheric circulation. Just one reason alone to caution against using MJO composites in isolation as a means to predict synoptic responses without consideration of the extra tropical momentum budget (i.e slow moving blocking patterns such as we have seen for many months) - and which in itself NWP do not always resolve quickly. One good reason why I do not actively refer to them at all in posting.

Massive energy flows, such as the processes that lead to the SSW in late winter, have long lasting repercussions in the way they imprint themselves on the weather patterns for many months ahead. Its the nature of NWP to be too progressive and try to eliminate these feedbacks

What we have seen this Spring and Summer so far is an excellent example of rossby wave energy dispersal via repeated active tropical momentum processes (f.e repeated again in April and increasingly looking to re-occur again later this month) firmly linking and re-cycling global to regional circulation anomalies.

Related to our own Atlantic/European region, this means we have seen a quasi 'semi-permanent' atmospheric state created by huge poleward +AAM anomaly sequences, and then actually locked in by the decelerating momentum of reverse -ve AAM phases - effectively fixing the pre-dominant longwave pattern in situ. A repeating highly amplified mutli wave global pattern has seen us, for once, in the warm air sequences of this merdional pattern.

In a way, its the same principle as winter 62/63 where -ve AAM phases locked in the cold pattern created by massive +ve AAM momentum processes into the stratosphere in the autumn and early winter.

These types of events are historically (relatively) quite rare and very much the exception to the rule. Seldom in the depth of winter do low angular momentum processes assist cold weather patterns and the same is true in terms of seldom providing downstream European blocking patterns in summer that give the best seasonal fine warm/very warm weather. This summer we have been blessed with an especially northward shifted sub tropical high regime that has held in situ and not behaved as would usually be expected according to upstream momentum signals.

Its this that makes July especially interesting with the potential July>August signal in mind in term of the processes likely to happen across the Pacific which imply a further surge of atmospheric angular momentum and next phase of rossby wave dispersal to top up blocking patterns. Models slowly now starting to pick up on that AAM tendency rally signals (and as described below).

.

With all this in mind, its a good idea not to take short term Pacific wind anomaly profiles as posted on this thread sometimes in isolation of the bigger picture and extrapolate these forward as an attempt to try to anticipate the pattern ahead.

Persistently warming sub and surface water anomalies in the Pacific look set to augment an ocean kelvin wave with an atmospheric MJO related kelvin wave sequence through July (in addition to micro scale cyclonic typhoon activity) which suggests a correction ahead to AAM and consequences for what happens to the existing pattern.

This is very counter intuitive to increased trades through the second half of July, and indeed suggest quite the opposite when indications persist that the atmosphere is set to finally imprint on the ocean signal to a more El Nino type of circulation -  ending two years of a La Nina standing wave.

So, using this evidence to try to build on further on earlier stated provisional thoughts in previous posts, what might it mean to the existing pattern in the extended period?   With the trade winds patterns weakened and imprinted by the tropical signal transferred eastward, this implies +ve Asian mountain torque and further jet extensions across the Pacific such as were seen from mid April (first warmth of the year) and again heading into June. First indications of this are now registering as frictional torque plot corrects upwards as signal that easterly trade winds are being scrubbed from the tropics.

Frictional torque leads mountain torque tendency as rossby wave dispersion travels to the extra tropics. For the time being though, tendency here is still negative, including  a-ve Asian torque reflecting the trade wind anomaly (ahead of corrective signal)

 

A return to a Pacific jet extension, further out, means the profile of the Pacific becoming increasingly cyclonic first and foremost (there is already typhoon activity in the Western Pacific) and then with time the downstream pattern reflecting this adjusted wavelength with a corresponding greater trough tendency in the Atlantic to our west. (And, as a future possible heads-up, NWP will quite likely be progressive with such a signal and try to blow out the blocking).

So, in this scenario (should it come to pass as evidence helps support) less domination of the Azores High likely - as a non-forecaster I might still indulge in also quietly suggesting that our friendly summer High becomes more continentally and Scandinavian orientated with emphasis of ridging from this central focus rather than from the SW. This leaves open the door for greater influence from heat from a southerly vector mixing it up with troughs attempting to undercut the heat. So maybe a more thundery aspect coming into the second half of summer at the same time perhaps that fronts engage the north west perimeters of the country with better 'success' than so far this summer?

We will watch and see how this unfolds anyway.

Hope this summer is also proving very much the type of thing that takes your fancy as much as my own. Keep enjoying it 

 

 

 

Edited July 2, 2018 by Tamara

[ChezWeather]

Lets hope the 12z GFS is over egging this feature 

Way out in week 3 mind 

[DR(S)NO]

Ah.... but this is the year of The Beast From The East !

Not saying it will happen... but everything just feels’ different ‘

Edited July 2, 2018 by DR(S)NO
Was replying to The Pits Post ... but wouldn’t quote

[DR(S)NO]

45 minutes ago, The PIT said:

That's the one where it's showing 33C at midnight. I think it's marbles are a bit wonky that far out. However there is a possibility of some record heat from this. As for plumes alas just mere shadows of what plumes used to be like and nowadays very rarely deliver.

 

[Frosty.]

Great post as usual Tamara..and speaking of Great, the GEFS 12z mean is GREAT for those of us enjoying this amazing spell which would just keep going until around mid July further south with day after day of mid / high 20's celsius and some 30c+ days too!..the azores high is being very friendly this summer..loving it

[Captain Shortwave]

I must admit the UKMO looks very pessimistic regarding the 850s, made especially so when we look at the ECM.

      

     

The ECM adds around 2C to the 850s off near enough the same surface pattern. High twenties pretty likely under blues skies and light winds on Saturday

Add a degree or so to Sunday;

   

To be honest the GFS seems to be overplaying how well developed thecut off low will become, other models have a weaker feature moving towards the Azores.

It still looks like turning very warm to hot regardless over the weekend and probably into the first half of next week.