Model output discussion - hot spell beckons but then what?

[MP-R]

It’s quite funny how these lows like to arrive on Fridays. First the 7th June, then 19th July and now 9th August. Perfectly timed to mess up weekend plans or events - this time the Bristol balloon fiesta. Not many flights will be had I don’t think.

Also looking quite cool beyond the weekend. Relatively warm for the south at least before then but that’s all irrelevant if it’s not sunny.

[Frosty.]

I went cherry picking and found a few decent charts for late August...  It's certainly an unsettled outlook but late August is still up for grabs and it won't necessarily be a poor end to summer just because thats how it seems currently!

[MATTWOLVES 3]

Last night's EC46 is on the money with the very unsettled conditions this week and weekend. The signs are that by the final 3rd of the month... Say the 23rd, is that pressure should gradually start to rise in the S/SW... This pattern looks to hold moving into September, I will point out that precipitation charts for the NW are at times a horror story! But there are most definitely better signs for areas away from that vicinity come the months end... Wouldn't at all be surprised to see a more pronounced NW/SE split moving forward beyond this point... All along way off, but the signal remains constant. 

[Man With Beard]

Any hopes of more settled weather for the final 3rd of August? Long way out, but the clusters rate the chances are fairly low, especially further north.

[Frosty.]

The Gfs 6z operational looks a bit better than the 0z with some decent ridging at times, mainly across southern uk, so yes it's a generally unsettled outlook but that doesn't preclude some spells of fine and warm weather!!!

Edited August 6, 2019 by Jon Snow

[Summer Sun]

Looking at the ECM weeklies it's looking like temperatures will be struggling at times with above average rain right through until week 4 the only exception is possibly the far south where we see a weaker signal by week 4 

A lot a rain on show for areas already hit by flooding and it looks like we'll be seeing a lot more issues with flooding over the next 3 to 4 weeks bar a massive change from current predicitions 

[MATTWOLVES 3]

6 minutes ago, Summer Sun said:

Looking at the ECM weeklies it's looking like temperatures will be struggling at times with above average rain right through until week 4 the only exception is possibly the far south where we see a weaker signal by week 4 

A lot a rain on show for areas already hit by flooding and it looks like we'll be seeing a lot more issues with flooding over the next 3 to 4 weeks bar a massive change from current predicitions 

There are signals for high pressure to build into the South come months end though.. Yes precipitation amounts are high in the NW. Personally I think the current EC46 is pretty much in line with the Exeter update. So it's not a complete doom forecast SS. 

[Polar Maritime]

GFS showing some ground frosts for the North after the Low swings through pulling in some cooler uppers. Some wintry showers for the Mountains I would of thought in this set-up.

[Summer Sun]

21 minutes ago, Mattwolves said:

There are signals for high pressure to build into the South come months end though.. Yes precipitation amounts are high in the NW. Personally I think the current EC46 is pretty much in line with the Exeter update. So it's not a complete doom forecast SS. 

Can almost guarantee that come early September things will improve once the kids go back high pressure and warmer temps will return

[MATTWOLVES 3]

1 minute ago, Summer Sun said:

Can almost guarantee that come early September things will improve once the kids go back high pressure and warmer temps will return

That's what I thought mate... Its sods law.. Mind you a nice September would be good... It can be warm in the day and cool at night, which I find bliss. 

[mb018538]

13 minutes ago, Mattwolves said:

That's what I thought mate... Its sods law.. Mind you a nice September would be good... It can be warm in the day and cool at night, which I find bliss. 

I've found September to be as good or better than August in a lot of recent years. Sure - it may be a notch or two cooler average/CET wise as you'd expect heading into Autumn, but the weathe in general has been more pleasant. August has probably turned into the most disappointing month of the year for expected/potential weather versus the reality. Give me some of those 1990's months please!

[Frosty.]

Hey I spotted a plume at the end of the GEFS 6z!!!!..longer term, last third of august showing hints of summer returning!!!!!

 

Edited August 6, 2019 by Jon Snow

[Don]

33 minutes ago, Mattwolves said:

That's what I thought mate... Its sods law.. Mind you a nice September would be good... It can be warm in the day and cool at night, which I find bliss. 

Summer like Septembers in recent decades have tended to be followed by mild winters.  That’s why I hope for an average to cool September this year.  However, as I said before, winter will probably be mild no matter what September is like!   I do also have a feeling next month will be warm and dry, though.

Edited August 6, 2019 by Don

[Polar Maritime]

Let's please discuss what the Models are showing in here, And use the Summer thread for thoughts/feels and what we don't or do like.

Thanks all.

[northwestsnow]

1 hour ago, Man With Beard said:

Any hopes of more settled weather for the final 3rd of August? Long way out, but the clusters rate the chances are fairly low, especially further north.

It doesn't look like August is going to be bucking the trends of recent years ..(ie rubbish).

Wonder if its likely sept/oct will be more summery than August?

[knocker]

The end of the week low. Last evening the MET were thinking two centers as well You can see where the strong winds warning in the south comes from

Edited August 6, 2019 by knocker

[Tamara]

17 hours ago, Singularity said:

Looks like those seeking settled summer weather will need to exercise a great deal of patience this month. 

The simplest route that I can see from current modelling involves stair-stepping westward progress of the mean 'cold' pool on the southern flank of the high latitude blocking across Greenland, making it a step further with each new trough formation. Those troughs also step west, and eventually - most likely sometime between the midpoint of the month and the start of the final week -  we escape their direct influence as ridges build across from the south or southeast.

Considering the tropical forcing at play, the reality may prove more complicated, perhaps involving a trough deconstructing and facilitating sudden ridge development close to our east or northeast.

The strong trade winds for the next 5 days correspond to a pattern change such as modelled, but not necessarily one that lasts more than a week after those trade winds wind down. The final third of the month remains up for grabs.

I agree very much with the premise of this post, and especially its conclusions

Signs that the tropical stratosphere is staging a warming ahead of typical seasonal transition.

 

Seasonal warming in the SH implies laying the pathway towards the start of seasonal cooling in the polar stratosphere. The precise increasing differential of temperature between the poles and the associated transport of ozone/assessment c/o Brewer-Dobson circulation to determine the potential strength of the new season vortex still some weeks away of course.

However, based on the legacy of a final warming of the stratosphere very late in Spring and into the early summer, that overstayed so many meteorological predictions this summer in terms of its dynamic tropospheric shock waves  - then there is going to be increasing pressure to flush out remaining warm anomalies within the troposphere, with the cooler anomalies that have been pent up higher in the stratosphere descending thereafter as the highest levels cool further

So in essence I think there is something of a further -ve zonal wind anomaly precursor in the troposphere/stratosphere boundary ahead of a more neutral AO regime(ultimately +ve) under way that makes things 'worse' in the short term wrt summer blocking and supressed Jetstream.

Add in the interruption to the weak walker cell low frequency signal circulation in the Pacific at the expense of  increased trade winds -

 

-,and in the absence (to date) of any high frequency tropical signal (MJO) to compensate this by helping adding extra supplies of westerly winds to the atmospheric circulation during mid summer, then its easy to see how angular momentum has been trending slightly below average for a while. This -ve wind-flow anomaly assists the upstream pattern becoming increasingly amplified, while this side of the NH at the expense of the higher latitude heights supressing the jet stream in our locale. Much of this has been discussed at length recently.

On the other side of the equation however -  disparity of SST anomalies shows sharp contrasts in the WPAC and the EPAC. Considerable warmth west of the dateline contrasts with neutral/slightly -ve anomalies east of the dateline

Why does any of this matter so far way downstream?

This disparity supports the weak walker cell re-emerging sooner or later c/o CPAC tropical convergence and ingredients for convection/deep thunderstorm development - and this translates to questions over the longevity of the amplified upstream pattern as momentum transport increases due to westerly wind bursts returning to the Pacific. At the same time as the AO begins a slow trend towards neutral and also alters the jet stream path

To add to the mix, the high frequency tropical signal is starting to show signs of activity following its mid summer slumber . The slumber c/o quite an active Indian Ocean monsoon season. The I/O intra seasonal signal assisting keeping a lid on atmospheric angular momentum and the trend towards the more La Nina-esque pattern that is spoiling Augusts middle third fortunes. There is discrepancy within the deterministic MJO modelling, with the GFS keen on amplified progression to the Pacific whilst the ECM exhibits what can be a problem bias to Maritime convection - but these are quite unreliable beyond 5 days or more anyway.

 

However the velocity potential (VP200) anomalies, a more consistent source of inspection for the purpose, continue to point towards propagation of a more active regime in the Pacific replacing the trade wind suppression of activity from after mid month. Note the movement of suppression across the tropical Atlantic and towards Indo/African Western Hemisphere as this is predicted to occur.

.

So there is increasing pressure from within the polar field to neutralise heights with time, and for a rally in angular momentum c/o a return to Pacific rossby wavelength control as summer season (not necessarily weather) draws towards its official close.

This does not present a clear cut prognosis at all for NWP evolution the further the month progresses.

Having spent the last few posts cautioning against taking each NWP suite et ensembles at face value - and especially extrapolating them too far forwards in time, I appreciate the difficulties in the context of this thread of that successfully being heard

But from my own point of view, and being naturally sceptical of NWP interpretation of diagnostic drivers, the outlook heading into the last third and especially last week/and end of August period is far from certain. Such scepticism includes the likes of the EC weekly, and its own suggestions of timings (and that of any other long term numerical modelling product).

Unsettled and not especially pleasant at all to mid month and shortly after? Yes, alas very much so. But as it stands the upcoming very volatile pattern, further augmented by an astonishing amount of ocean heat north of 30N in tandem with hot continental landmasses to sharply define thermal boundaries, nevertheless risks in its dramatic context, to obscure and risk overdoing a signal that appears to have longer term drivers acting against it.

Something eventually gives in my opinion - its a question not of if, but when? That is the most difficult question.

[philglossop]

7 hours ago, MP-R said:

It’s quite funny how these lows like to arrive on Fridays. First the 7th June, then 19th July and now 9th August. Perfectly timed to mess up weekend plans or events - this time the Bristol balloon fiesta. Not many flights will be had I don’t think.

Also looking quite cool beyond the weekend. Relatively warm for the south at least before then but that’s all irrelevant if it’s not sunny.

Plymouth Pride on Saturday. It was washed out last year,  this year plenty of Drag Queens will be holding on their wigs! 

[knocker]

Regarding the beginning of next week the gfs has a completely different interpretation than this morning's ecm with a new upper trough crossing the Atlantic by midday Monday and phasing with our static upper low to the north and thus another quite intense surface low effecting the country with strong winds and rain. This should of course remain a watching brief at the moment until the detail gets sorted.

Edited August 6, 2019 by knocker

[Polar Maritime]

Yes Knocker was just looking at that myself, A striking difference to the 6z.

[Methuselah]

So, did the 00Zs pick-up on a warming trend? How would I know? Once you get past August 14, the 850s and SLPs look like Boris Johnson's Polygraph test...?

   

   

[knocker]

The ecm is not making much of any new low at the beginning of next week. It has the negatively tilted upper trough swinging around the static low over Iceland which eventually starts to slip south. A minor disturbance does develop in the base and track NE Sun/Monday and an Atlantic front sneaks in by Tuesday so essentially showers and sunny intervals over the former two day with perhaps a longer spell of rain on Tuesday. But as previously stated this awaits some firming up

[mb018538]

Rubbish ECM out to day 10 again tonight. Not totally low pressure dominated, but on the cool side with NW then N winds by the end. We probably won’t even see any good day 10 charts for a few more days at least. Perhaps the pattern relaxes a little into the final 7-10 days of August, but remaining disappointing until then.

[Polar Maritime]

The GFS shows the Atlantic Low next Tuesday making for a more direct path over the UK on this morning's run.

Beforehand some heavy rainfall to come Friday, With flooding once again very possible as shown by UKV. Some very active weather on the way in the medium term to keep tabs on..

Edited August 7, 2019 by Polar Maritime

[tinybill]

the weekend  looks  very  nasty , but i think the next storm we very must have to keep a eye on is about 174 hr,and even  to the end of Augest  we could write  it off as its not looking at all nice

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

 

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

Edited August 7, 2019 by tinybill