Model output discussion - hot spell beckons but then what?

[Captain Shortwave]

So unsettled for the next couple of days, some lovely downpours mixed in with this. But a window from Friday that could last throughout the weekend where conditions look mostly fine and dry. Potentially very warm if we see some good sunny spells.

next week looks like we see a slow transition to westerlies with low pressure parked to our north west.

[knocker]

0800 UTC

[cheshire snow]

1 hour ago, Djdazzle said:

So glad that the record was broken so that July now holds it. August these days is a poor excuse for a summer month, and the models look like (although they could change) delivering our 17th consecutive poor / average one.

Have to agree unfortunately however September in recent years have been very good especially around these parts.

C.S

[Froze were the Days]

Wow!...what an exciting ECM run this morning if you like low pressure anchored out to the west/west north west for the foreseeable and according to the 0z even further. I should think going by that many southern and eastern areas would be largely dry and fairly warm though, the typical NW/SE split - yawn!

[northwestsnow]

4 minutes ago, Froze were the Days said:

Wow!...what an exciting ECM run this morning if you like low pressure anchored out to the west/west north west for the foreseeable and according to the 0z even further. I should think going by that many southern and eastern areas would be largely dry and fairly warm though, the typical NW/SE split - yawn!

Very poor pattern for those further north and west, i would imagine NW Britain will be very wet over the coming 10 days, at least.

Such a shame, another large chunk of the summer holidays looks a write off round these parts.

Hopefully those further south and east will escape the worst of it.

[Frosty.]

The Ecm 0z operational shows a nice ridge later this week bringing a window of drier and sunnier weather which would be welcome respite..the uppers (850's) look perfectly acceptable for the time of year with plenty of warm surface conditions and probably rather humid at times too...so, there's rain, there's flooding, theres thunder, there's sunshine and there's warmth plus we already have a record breaking summer with still another 6 weeks of summer to come if you count the first half of September which often brings a late taste of summer..time for more records?.Ahhhaaaaaaaaaaaa!!!!!!!!.!

Edited July 30, 2019 by Jon Snow

[mushymanrob]

well these charts are just about as bad as you could create for this stage of the summer. they are a very long way from being charts that would allow a lengthy settled sunny warm dry spell, let alone heat. pretty ominous really as we enter august, which looks strongly like being yet another poor one.

[northwestsnow]

6 minutes ago, mushymanrob said:

well these charts are just about as bad as you could create for this stage of the summer. they are a very long way from being charts that would allow a lengthy settled sunny warm dry spell, let alone heat. pretty ominous really as we enter august, which looks strongly like being yet another poor one.

I posted as much earlier ...

Too much blocking at northerly latitudes... hopefully it will abait as we move through the month..

[MATTWOLVES 3]

The Ec46 from last night indicates a rather unsettled 1st half of August with low pressure situated to the W/NW... obviously this would entail showers and spells of rain at times, especially further North and West. Temps quite cool in the North, but more like average or slightly above further S/SE. The final 3rd of August is showing an improvement towards the S/SW with increasing heights and temps on the warm side at times... So at this stage perhaps a month of 2 halves... Fittingly if we had another major warm up come the final 3rd of August, that would be the 3rd time during this summer that a major warm up had occurred at the end of each month!! I quite like the sound of that.... Summer going out in style...

[Tamara]

On 27/07/2019 at 16:25, Tamara said:

The modelling has shown itself this summer as susceptible to wanting to keep the pattern too flat for too long with the phasing of these lows and instead the sub tropical ridge proves more resilient ahead of it. This is something to watch in the snapshot in time ensemble suites and not take too much at face value from the more immediate suites - but maybe instead judge them from how they evolve during the coming days ahead.

Persistence factors alone do not of course guarantee past trends will be mimicked in future trends.  Next weeks blocking programmed to the north is likely to migrate westwards with time, in tandem with pressure falling over Scandinavia and also tending to migrate that low pressure west to phase with approaching troughs in the Atlantic . This initially looks set to flatten the pattern to create the illusion of a longer term procession of lows.

But as the pattern retrogresses, then this increases the likelihood that a follow up trough will, ultimately, like previously seen this summer, deepen in western/mid Atlantic and so a re-occurring downstream sub tropical ridge response accordingly gains traction, in time, with the modelling.

At the moment, the modelling is best 'seeing' the phasing of falling of pressure across Scandinavia (from its latest downstream ridge peak) with the  trough(s) approaching in the Atlantic next week. The caution is in extrapolating and making assumptions too far ahead from this - and so not a bad thing to be mindful of the risk of NWP persisting, in error, of this synoptic stage for too long.

Further self-quoting from the other day, but it has the well meaning intention to reiterate the theme of 'snapshots in time' instead of taking every operational/ensemble/cluster suite at face value, These also extend to the associated upper air pattern representations which also are subject to change as  numerical modelling keeps reading the diagnostic elements (comprising fluxing tropical and extra tropical wind-flow phases) over time. 

Extrapolating all of the numerical modelling representations ahead for unduly long periods of time is fraught with error when margins of change can sometimes emerge over periods of days at a time, rather than every 6/12/24hrs at a time

The bolded extracts in the quoted post are simply for particular emphasis.

An interruption to the low frequency tropical  walker cell signal in the Pacific that has dominated much of July (and that propped up the Atlantic trough/our downstream ridge) has been in progress and is set to persist into the new month with the renewed increase in trade winds over the Pacific clearly evident since the end of last week (shaded blue in and around the dateline)

 

 

,...This will be helping propagate -ve AAM anomalies to higher latitudes based on a slump in global atmospheric angular momentum . So essentially this slump is now catching up on us

- and as a consequence helps re-invigorate blocking at higher Greenland latitudes and this side of the Northern Hemisphere inviting a path towards a supressed Jetstream and low pressure phasing between the Atlantic and Scandinavia by next week. Therefore a trough close to the NW of the UK has support in this respect.

However, temperatures throughout this period look quite respectable and warm at times - especially perhaps this coming weekend before the pattern flattens out (as expected) so nothing in those respects that is poor by summer standards. (Also see the conclusion of this post).

Personally, for what it is worth, I'm not attaching confidence in a Scandinavia/UK trough as any long term sustained solution encompassing 'the rest of summer' - and continue to think that the numerical modelling risks over dwelling on this signal. For me anyway, its a case of sitting on hands, and letting the scenario play out. The numerical models are not going to drop it immediately within a day or two,  which further envisages in my mind the moans thread busier with standard writing (or repeating) of summer obituaries - but that is where the risk lies in interpreting/making assumptions about longevity. Summer 2012 style, did not materialise following the first two thirds of June 2019 after all....And whilst the last third of summer beckons immediately, there remains plenty of time for summer-like weather

So as was the case in June, its also too soon to summon the meteorological priest at this time

It remains likely that the pattern will keep retrogressing, as suggested previously, so that ultimately at some stage the jet stream will be forced to lift a trough further NE and invite a further ridge response towards Europe - and irrespective of any trough signal over Scandinavia. This is especially true if tropical activity in the southern Atlantic is created by the actions of a convectively coupled kelvin wave activity passing through Africa from the Atlantic - such a CCKW is occurring during the first half of August.

This type of activity often throws curveballs in modelling at short notice during many late summers and as an interruption to mid Atlantic ridging and Scandinavian trough scenarios and cuts short their attendant less than desirable cool changeable north westerly winds, besides which, are often over modelled at distance. Those - that are one of the culprits for summer obituaries

There is a lot over the coming 10 days that could,and conceivably will, alter the apparent prognosis for August as a whole,. Whilst an unsettled spell is supported and it may also turn cooler for a while around the second week and towards mid month (pending tropical developments)  it makes sense in my opinion to compare ensemble suites and clusters over that opening week to 10 days as an evolutionary way forward, rather than taking each at face value individually, on repeated intra day intervals and drawing conclusions/extrapolating the snapshots in time too far forwards

Notwithstanding the above suggestions about not taking individual modelling suites at face value, even if I break my own rules at this early time (as subject to the further evolution as discussed) there is nothing exactly terrible anyway about the latest temperature ensemble set assessed against the implied (and fully expected) flatter pattern phase for the second week August period. Its maybe forgotten just how very much cooler than this the early to mid June period was.

[danm]

Looking at the semi reliable timeframe (up to day 5/6/7), it’s a case of better further SE, less good further NW. So typical, average UK summer weather (particularly in August when weather in the NW tends to start going downhill). 

Thursday onwards and into the weekend provides most parts of the country with a window of fine, settled and quite warm weather - once this low over the S/SW today clears off into the North Sea. 

Early next week (days 6 and 7) look like moving towards a NW/SE split with the low in the eastern Atlantic slowly making inroads to park itself just to the NW of the UK. Beyond that is la la land, although with the anomaly charts showing a lot of northern blocking you wouldn’t bet against the low continuing it’s slow migration eastward to park itself right on top of us. Plenty of water to pass under the bridge before then though, and let’s remember there were some signals for this sort of set up even in early July, yet this month has largely been a good one (with a record breaking day thrown in for good measure). 

Anyway, reliable timeframe shows an improving picture after the awful weather we have today and tomorrow over most parts. 

[Frosty.]

There are hints on the longer term GEFS 6z mean that the azores high might ridge in which is usually the prelude to a summery spell in the uk...in the meantime it looks like a nicer spell later this week including the weekend and further ahead looks mixed with some ridging / showery troughs and temperatures on the warm side of average at times, probably most of the time across southern uk!!!

Edited July 30, 2019 by Jon Snow

[knocker]

Some high SST anomalies around at the moment, particularly in the Baltic, courtesy of the recent heat wave

[knocker]

The showers/storms swirling around within the structure of the low

Edited July 30, 2019 by knocker

[Scorcher]

4 hours ago, northwestsnow said:

Very poor pattern for those further north and west, i would imagine NW Britain will be very wet over the coming 10 days, at least.

Such a shame, another large chunk of the summer holidays looks a write off round these parts.

Hopefully those further south and east will escape the worst of it.

North West Britain yes, but for us in NW England it's not looking bad at all, especially after tomorrow. We may get a shower or two on Thursday (good chance of dodging them altogether though) and Friday and Saturday look dry and warm for the most part. Also temperatures very reasonable, even first thing in the mornings. Beyond the weekend, who knows, still a lot to be decided.

[Frosty.]

First thing to say about the Gfs 12z operational for the next week or so is it's on the warm side with temps into the low 20's celsius (21-24c) and it becomes warmer still by sun / mon, especially further s / se into the mid 20's celsius range (25/ 26/27c) around 80f and increasingly humid. It also becomes less showery towards the end of this working week into the weekend with more in the way of dry weather and sunshine before the showers become more intense again but certainly a better spell later this week compared to currently..and no probs with the temperatures....it does trend cooler beyond a week ahead but that's heading into low res!!!

Edited July 30, 2019 by Jon Snow

[Methuselah]

The GEFS 12Z ensembles don't really suggest any imminent 'woodshed surprises', though the coming  weekend's warmup is likely to be followed by something of a cooldown...Exciting innit!

   

   

If only I could understand teleconnections the way @Tamara does!

[knocker]

A quick snapshot of the weekend with the ecm Some showers around in the north on Saturday and a weakening warm front does encroach from the west with some patchy rain before fizzling out. This is followed by a cold front which is down the Irish Sea by 0600 Sunday and continues east to bring rain to much of the country but not the south east

 

[MATTWOLVES 3]

40 minutes ago, Ed Stone said:

The GEFS 12Z ensembles don't really suggest any imminent 'woodshed surprises', though the coming  weekend's warmup is likely to be followed by something of a cooldown...Exciting innit!

   

   

If only I could understand teleconnections the way @Tamara does!

Hey Pete you know more than me... When I first heard the words... Teleconnections... ive gorra be honest, I thought it was something do with British Telecom.... Dohhhhh..... Luckily tams has at least helped me understand it more. Tonight's ECM shows an improvement out to the end of the week and weekend. Quite warm as well to the South. Next week low pressure becomes anchored to the NW... So showers and some rain will be most probable especially in the usual places... Towards the end the pattern flatters a tad... Perhaps some cooler air moving down from the North... Hey up... Winter chasers will be out in full effect before much longer... Hold ya horses guys... Let's get August out the way first So basically the weather stays a bit on the unpredictable style for the opening of the new month... Still hopefull of pressure to rise from the SW towards mid month... Plume 3!! I wouldn't be surprised at some stage. One last hoorahh. 

[Methuselah]

6 minutes ago, Mattwolves said:

Hey Pete you know more than me... When I first heard the words... Teleconnections... ive gorra be honest, I thought it was something do with British Telecom.... Dohhhhh..... Luckily tams has at least helped me understand it more. Tonight's ECM shows an improvement out to the end of the week and weekend. Quite warm as well to the South. Next week low pressure becomes anchored to the NW... So showers and some rain will be most probable especially in the usual places... Towards the end the pattern flatters a tad... Perhaps some cooler air moving down from the North... Hey up... Winter chasers will be out in full effect before much longer... Hold ya horses guys... Let's get August out the way first So basically the weather stays a bit on the unpredictable style for the opening of the new month... Still hopefull of pressure to rise from the SW towards mid month... Plume 3!! I wouldn't be surprised at some stage. One last hoorahh. 

Lol, Matt: When I first came across them, I was instantly drawn to the antics of the Spoonbender Extraordinaire, Uri Geller!

We live and we learn, mate!

[knocker]

Both the ecm and gfs 5-10 anomalies are indicating an unsettled latter half of the det runs with the jet running a fair way south under the Greenland block and low pressure dominating the eastern Atlantic Temps around average

[Spurry]

7 hours ago, knocker said:

Some high SST anomalies around at the moment, particularly in the Baltic, courtesy of the recent heat wave

I can vouch for that , we were swimming off the west coast of Sweden last week and it was not chilly at all

[Singularity]

The standoff between the 7+ day modelling and forcing-based anticipated pattern development continues... though there's room for a bit of one, then the other, if you ask me.

You see, the models continue to take the trough that's close by early next week east through the UK during the following 3-5 days, but the next trough out west isn't being moved along as quickly as before, and has been adjusted south and west quite a bit, with some elongation down west of Europe in evidence on the ECM run especially.

Our breaks free from unsettled regimes in June and July, toward something drier and much warmer, have been achieved via this divided trough movement; one clears away while the other digs down west of Europe. This allows a ridge to build across N. Europe even with high pressure across Greenland. It's helped that the Greenland heights have tended to be overdone in the 6+ day range too (except in the extraordinary case currently unfolding, which was fuelled by last week's record-breaking hot shot).

 

So it could be that we see another run of rainy days next week, perhaps markedly cooler for a time too, but with this soon giving way to a big warm-up and dry-out. This being something the models are currently more or less blinded too by their systematic bias with the tropical forcing (too much Africa-Indian Ocean forcing versus Pacific).

I realise I'm being a bit bold here... so will finish up with a classic big old August caveat; tropical cyclones could distort the pattern responses and serve to delay and/or moderate the extent of high pressure building across N. Europe. Or they could bring it forward and/or strengthen it! I can dream.

[Methuselah]

8 minutes ago, Singularity said:

The standoff between the 7+ day modelling and forcing-based anticipated pattern development continues... though there's room for a bit of one, then the other, if you ask me.

I realise I'm being a bit bold here... so will finish up with a classic big old August caveat; tropical cyclones could distort the pattern responses and serve to delay and/or moderate the extent of high pressure building across N. Europe. Or they could bring it forward and/or strengthen it! I can dream.

As for your first paragraph, S, I'm not sure there is a standoff?

But, the last one? Yes, I agree absolutely!

[knocker]

The North Atlantic 500mb and surface analysis for midnight and the 0400 UK chart

As can be seen the low is mow centred over Hull and it will not move that far east as it continues to fill. Thus the sometimes heavy showery rain will persist over northern and north east England throughout the day, turning more showery later. But by then heavy showers and storms will effect western Scotland and NW England, courtesy of the wrap around occlusion. Much of Wales. the south west/south of England and northern Scotland will be dry and see the best of the weather. Still breezy over much of England and Wales

The thundery showers will dissipate this evening and any rain confined to the east coast as the low continues to move slowly east overnight

So tomorrow looks like being a dry and much better day for many areas with a fair bit of sunshine and getting a tad warmer but showers are likely to pep up in many areas through the day, particularly in north west regions, with maybe the odd storm

By midday Friday the UK is sitting a col as the low finally loses its identity, so very light winds and sunshine and showers will be the order of the day with the latter confined to the convergence zone in the north

A not dissimilar story on Saturday but the upper low to the west is taking closer order and a surface trough will bring some showers to western regions

By Sunday the upper low is a tad further east and a weakening surface occlusion will bring showery rain to western regions that will move gradually east during the day with perhaps some quite intense thundery outbreaks by the afternoon, which will be quite warm in the south east

 

Edited July 31, 2019 by knocker