Model output discussion - hot spell beckons but then what?

[danm]

Morning runs show a mixed bag. A wet weekend for many (bar the far SW) then drier, brighter and warmer on Monday before turning unsettled Tues-Thurs. End of the working week and into the weekend pressure builds as the low drifts west, so we should see sunnier and warmer weather for a few days. Beyond that is a lifetime away. 

Edited July 27, 2019 by danm

[Methuselah]

Here are this morning's GEFS 00Zs...not bad and not great?

   

   

But, given that however August turns out, it'll be compared to last week, it has little chance being judged as anything but a 'washout'...

[mushymanrob]

1 hour ago, mb018538 said:

Starting to look like another poor August is shaping up - literally nothing in any output at the moment to say that the first couple of weeks won’t be pants. All of this thanks to the heatwave. Price to pay and all that...

eh?... how is the heatwave responsible for a poor august?.. the demise of it will, is doing, as pretty common resulted in a few miserable days before the pattern emerges that will see us into august. the heatwave didnt cause that pattern.. the expected low pressure domination. the heatwave was a result of the synoptic pattern, the heatwave didnt cause the synoptic pattern.

however it is looking ominous that august yet again will be poor..  if these predictions are accurate, then its a long way off from and high pressure domination.

Edited July 27, 2019 by mushymanrob

[Summer Sun]

Looks like the heaviest rain will be a bit further east than some models were showing on yesterdays 12z already had torrential rain here in Darlington and more is on the way looking at the radar and WRF/GFS

[northwestsnow]

1 minute ago, Summer Sun said:

Looks like the heaviest rain will be a bit further east than some models were showing on yesterdays 12z already had torrential rain here in Darlington and more is on the way looking at the radar and WRF/GFS

Good spot Gavin...

Thankfully for my location , the models have shifted the bulk of the rain further NE..

[mb018538]

6 minutes ago, mushymanrob said:

eh?... how is the heatwave responsible for a poor august?.. the demise of it will, is doing, as pretty common resulted in a few miserable days before the pattern emerges that will see us into august. the heatwave didnt cause that pattern.. the expected low pressure domination. the heatwave was a result of the synoptic pattern, the heatwave didnt cause the synoptic pattern.

however it is looking ominous that august yet again will be poor..  if these predictions are accurate, then its a long way off from and high pressure domination.

Follow the charts through and look where all the heat from last week ends up - into the Arctic circle which has blown up another Greenland high and forced the jet south again.

[Mr Frost]

Wet day ahead here - chucking it down currently!

Latest GFS run is pretty shocking for Scotland after the next 5 days or so. (Above average temperatures though in the short term and dare I say it...USABLE weather and also the risk of a thundery shower)

I am at the point now that IF August does turn out poor then so be it - this Summer for me has been fantastic so far. (Two plumes, highest temperature recorded 28c and numerous days above 26c, plenty of sunshine and a good few thunderstorms) 

It has been a great Summer for model/chart discussion and I have learned loads from all the fantastic posts in this thread over the past 7 weeks or so.

Have a good weekend!

[damianslaw]

A word on current synoptics - a cold snow lovers dream if this was Dec-March, a slow moving front stalling over some parts with cold air aloft and on its rear with northern blocking.. alas its July. Some places would be experiencing a very long lasting heavy snowfall - rare to see such synoptics Nov-Feb especially, perhaps less so March, but much more so come the spring-summer months.

It has been a marked major switcharound - in two days, quite a classic one, from severe heat to quite cool conditions.

[mushymanrob]

1 hour ago, mb018538 said:

Follow the charts through and look where all the heat from last week ends up - into the Arctic circle which has blown up another Greenland high and forced the jet south again.

its the high pressure that caused the heat thats migrated up there. the high pressure caused the heat, the heat didnt cause the high pressure.. nit picking i know, but it was the behaviour of the high pressure thats resulted in a strong northern block.

[MP-R]

It’s an unusual setup at the moment but even more unusual if it were March given how Atlantic dominated the month is. Perhaps more expected in mid Jan - Feb when Atlantic fronts come up against a big block.

This slack pattern looks set to continue to months end at least with perhaps some convective potential early-mid next week depending on how much clag is left over.

[MATTWOLVES 3]

Maybe a little paranoia setting in on here at present. Just because HLB was the culprit behind a poor bulk of June does not mean it will be the culprit once again! The next few days looking mixed for sure, later next week low pressure should back West a a tad..... Meaning better conditions with warm sunny spells. Beyond that low pressure perhaps becoming anchored to the NW... for me a classic NW/SE split.... Rather disappointing in that neck of the woods.... Further South and East, drier warmer, and perhaps at times very warm conditions at times from the near continent. Certainly not seeing a June sequel!! That pattern was well and Truelly broken weeks ago. Never say never but I can't call a write of August on current output, that and the fact it doesn't even start for nearly another week. 

Edited July 27, 2019 by Mattwolves

[I remember Atlantic 252]

2 hours ago, northwestsnow said:

Good spot Gavin...

Thankfully for my location , the models have shifted the bulk of the rain further NE..

I was just thinking the opposite, further west than forecast, was meant to be only east coast, SE all the way up to E Scotland, but instead it's covering most of Wales

[northwestsnow]

19 minutes ago, I remember Atlantic 252 said:

I was just thinking the opposite, further west than forecast, was meant to be only east coast, SE all the way up to E Scotland, but instead it's covering most of Wales

Well its throwing it down here now so yes, i think you are right

[Methuselah]

A kinda different-looking outlook, from today's GFS 06Z...Will it 'deliver'? Who knows?

   

[shaky]

31 minutes ago, Ed Stone said:

A kinda different-looking outlook, from today's GFS 06Z...Will it 'deliver'? Who knows?

   

Hmmm me like!!those blues are already getting there act together north of us!!cant wait!

[Methuselah]

Going from the GEFS 06Z ensembles, the operational is going off on its own...

   

   

Whatever, I guess time is fast running out, for all those who 'predicted' a summer just like 2012!

[Singularity]

Can't mind anything in the tropical teleconnections to suggest that HLB will necessarily force a mainly poor weather pattern for 1st half of August. Not a lot pointing the other way either, but ore than there is toward the cool and unsettled outcome. I suspect the models are, yet again this summer, showing bias toward Nina-like behaviour during times of weak forcing with a 'gentle' Nino standing wave competing against others of similar strength.

For now, I'm focusing on the shorter-term. The LP incoming for Tue is very interesting in that it behaves more like a tropical cyclone than our usual systems. It's so compact - perhaps it will have some degree of warm core? Making it partially tropical. Could bring some lively downpours if so.

 

Then we get to the question of 'where will it park up' as the westerlies capitulate (yet again!) and it comes down to the phasing of various lows within troughs to dictate the location of near-static ridges and troughs. This time it comes down to a couple of lows out in the N. Atlantic; if they merge, they amplify the trough-ridge combination with the ridge being across the UK, meaning the LP over us is eased out to the east. If those lows stay apart, that push to the pattern doesn't materialise, and we wait for the low to gradually fill in-situ. At least it's a 'warm' low; temps still look to do pretty well in sunnier breaks, reaching near or above the LTA for many parts (provided you apply a +1 or 2*C bias adjustment (a matter of judgement) to the GFS/FV3 raw output).

It's that kind of setup where if you have time off, you have to keep a close track of things and plan around short-range developments. Can be frustrating, but hey, it's the British summer!

[I remember Atlantic 252]

4 hours ago, Summer Sun said:

Looks like the heaviest rain will be a bit further east than some models were showing on yesterdays 12z already had torrential rain here in Darlington and more is on the way looking at the radar and WRF/GFS

those models seem miles out, it's way further west than that

[Cheshire Freeze]

5 hours ago, East_England_Stormchaser91 said:

Tuesday looks like the next bout of interest, convective wise. Could be one of them classic days with CB’s going up like popcorn from the word go, circling round the country under quite slack winds and giving some half decent storms in places. A setup that has often seen funnel clouds produced in the past too. 

Yes and a pattern that featured prominently around the turn of the decade 2007-2012. 

It just feels like we've gone back to that period weatherwise- the expansive -AO and at times -NAO this summer adding weight to that thought.

[Fitzwis]

1 hour ago, Singularity said:

Can't mind anything in the tropical teleconnections to suggest that HLB will necessarily force a mainly poor weather pattern for 1st half of August. Not a lot pointing the other way either, but ore than there is toward the cool and unsettled outcome. I suspect the models are, yet again this summer, showing bias toward Nina-like behaviour during times of weak forcing with a 'gentle' Nino standing wave competing against others of similar strength.

For now, I'm focusing on the shorter-term. The LP incoming for Tue is very interesting in that it behaves more like a tropical cyclone than our usual systems. It's so compact - perhaps it will have some degree of warm core? Making it partially tropical. Could bring some lively downpours if so.

 

Then we get to the question of 'where will it park up' as the westerlies capitulate (yet again!) and it comes down to the phasing of various lows within troughs to dictate the location of near-static ridges and troughs. This time it comes down to a couple of lows out in the N. Atlantic; if they merge, they amplify the trough-ridge combination with the ridge being across the UK, meaning the LP over us is eased out to the east. If those lows stay apart, that push to the pattern doesn't materialise, and we wait for the low to gradually fill in-situ. At least it's a 'warm' low; temps still look to do pretty well in sunnier breaks, reaching near or above the LTA for many parts (provided you apply a +1 or 2*C bias adjustment (a matter of judgement) to the GFS/FV3 raw output).

It's that kind of setup where if you have time off, you have to keep a close track of things and plan around short-range developments. Can be frustrating, but hey, it's the British summer!

A very interesting LP indeed with strong to gale force winds too for the NW of France, SW England and the Channel Islands 

Edited July 27, 2019 by Fitzwis

[shaky]

2 hours ago, I remember Atlantic 252 said:

those models seem miles out, it's way further west than that

It is riduclously further west than the model posted above!!cant believe how wrong that wrf model is at such short short notice!!ecm was bang on the money at the moment!!

[Tamara]

Looking back at a previous post last weekend, and some thinking expressed back then, its clear that the lesser progressive solutions did lead the way in some erratic modelling that was forced into some impressive westward corrections.

The closer detail reveals that this weekend is turning out wetter and therefore cooler than could have been anticipated at such a range, and across what is a microcosm of an area in relation to deciphering the Atlantic and European pattern. However, this rather distorts the bigger picture which shows that the very hot airmass has proved every bit as difficult to shift eastwards as these lesser progressive solutions suggested. Indeed it is this same slowness that has resulted in the stalled front and associated rainfall in evidence today and into tomorrow for quite a few of us.

The next thing to say, is that very many contributions and updates from a wide range of posters has made this, and other threads, following the modelled progress of the heatwave, an excellent read this week - and so in my opinion a lot of credit and thanks is due to a large number of members for some very detailed discussion and debate

Its been an astonishing week - not just for the heat itself, but also ( just for example) the outflow winds from thunderstorms which actually exacerbated that heat on Thursday evening associated with active and prolific 'dry lightning'.  These strong outflow winds were picked out by high resolution models  - as the EML theta plume (Elevated Mixed Layer) very gradually destabilised set against the very high upper air temperatures that had been 'capping' it - and have been taking so long to displace eastwards

Looking ahead, in my opinion a main theme of this summer stands a good chance of repeating itself. The recurring  'spasmodic' blocking of this summer previously discussed c/o a highly unstable polar profile keeps duelling with a very organised low frequency walker cell in the tropics that equally persists in renewing sub tropical ridging to our mid latitude.     At the same time according with this, and with our SST signatures helping, an Atlantic pattern fails to sustainably send a procession of lows under any block for a length of time, as one might expect with recurring higher latitude blocks, and instead sees follow up low slow on approach and give the sub tropical high every opportunity to ridge into the void ahead of it. 

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.

On that basis, the present fall in pressure over Europe (created by a displaced arm of the jetstream digging southwards, elongating the trough that was to the NW of the UK and gravitationally forcing its new centre of low pressure into the continent) represents the conclusion stage of a repeating cycle that commened at the start of summer, progressed its second cycle through July to its present end stage, and over the coming 10 days is looking set to commence its third cycle. 

The differences between the first two cycles has been that seasonal wavelength changes vs the tropical/extra tropical windflow circulation on the jet stream (the low frequency walker cell and convectively coupled kelvin wave activity in the Pacific) have helped incrementally back the pattern westwards. This trend takes us to the third cycle.

So that :

1) In June we saw the trough directly over us, and then immediately following up were still subject to cool air advection influence with the very high uppers that followed.

2) During July we have seen the trough resisted close by to our west. Hence the least progressive solutions verifying and the very warm/hot air advection managing to stick long enough to share the noteworthy conditions that mainland Europe saw in June

3) As August progresses our third tropical/extra tropical cycle of the summer, there is a reasonable chance that we may see a  trough sequence further displaced to our west and a more prominent late summer anticyclone influence from Western Europe/Scandinavia. Especially perhaps if some activity in the tropical Atlantic assists in the process.

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.

Too soon to suspect  August may follow any alleged underwhelming tradition, even if the ending of July and heading into the new month might appear to be getting off us off to a (relatively) unremarkable start. But temperatures still look respectable over the coming period and perspective has to be set against the spectacular events of last week

 

Edited July 27, 2019 by Tamara

[Methuselah]

The GFS 12Z doesn't appear to portend a disastrous start to August:

   

 

[danm]

2 minutes ago, Ed Stone said:

The GFS 12Z doesn't appear to portend a disastrous start to August:

   

 

And neither does the UKMO:

[danm]

GFS looking good post Wednesday, plenty of fine weather next weekend: