Model output discussion - hot spell beckons but then what?

[Mike Poole]

Well it looks to me that the ECM ensembles support the op run, looking at the mean at T168 and T240:

Shaping up for a nice September, let's hope so, always the most reliable month!

[Frosty.]

Tonight's Ecm 12z ensemble mean is really great for southern uk longer term as it shows high pressure and becoming very warm, really compliments the operational...fingers crossed, summery weather is on the way !!

Edited August 18, 2019 by JON SNOW

[knocker]

Indications with the EPS 5-10 mean anomaly of the upstream amplification and quite a strong westerly uppe flow across the north of the country as the subtropical high becomes more influential Given the source of the airmass temps trending above average and some quite pleasant weather albeit perhaps not so much in the north. This would appear to be a transient adjustment as the pattern moves east through the extended period and thus perhaps more changeable but nothing particularly onerous lurking in the woodshed and temps still a shade above average

This evening's NOAA is so so with this

[Blessed Weather]

A notable divergence of forecasts for the coming Bank Holiday weekend between the big two models. The 3 day mean of the 500mb height anomaly for the 25th - 27th August highlighting this, with ECM mean (on the left) high pressure dominated whilst the GFS mean no doubt reflecting its anticipation of a deep low pressure arriving over the UK on the holiday Monday:  

3 day 500mb mean 25th - 27th:

A selection of today's 12z Operational output for Mon 26th suggests it's the GFS that's out on a limb on this occasion, with other models tracking the low further north of the UK:

ECM  GEM 

JMA  GFS

[knocker]

The North Atlantic 500mb and surface analysis for midnight and a forecast sounding and convective cloud heights for later today

The low is slowly moving away to the north but for today the UK remains in a breezy north westerly airflow and thus a continuation of the showers currently effecting western regions, particularly N. Ireland and Scotland. But during the afternoon thundery showers may develop over central and southern England as the above sounding and convective cloud forecast confirm the possibility. But generally eastern regions will remain dry and sunny.

The showers will tend to dissipate tonight but a few still lingering around western regions

Showers will continue for a time in the north on Tuesday courtesy of the trailing occlusion whilst the rest of the country remains dry but later on rain from the fronts associated with the low east of the tip of Greenland will effect western regions. Note the twin flows around Grreenland

The rain will become sporadic as the front(s) weaken overnight Tuesday through Wednesday but developments are occurring in the Atlantic. The low to the NW has tracked a little east and the associated occlusion will bring moderate rain to norther regions later on Wednesday with only the far south remaining dry. Meanwhile another upper low has tracked into the western Atlantic from Canada

During Thursday and Friday the Atlantic troughs tend to merge as the subtropical high zones start to stir resulting in the north of the UK staying relatively breezy with some showery activity whilst the south, with less wind, stays fry with the south east becoming quite warm on Friday

 

 

[knocker]

There still remains a lot of uncertainty vis the detail for the holiday weekend and I'm far from convinced that the gfs is on the money, or even near it, as it continues to track the upper trough across the UK resulting in showery weather becoming a nasty little low on Monday. For what it's worth this is the outline

[knocker]

I may well have done the gfs an injustice. The ecm does track the upper trough across on Sunday, but more to the point tracks another intense upper low in the Atlantic on Monday so certainly no amplification of the subtropical high here

[Frosty.]

The Ecm 0z operational shows a nice warm up later this week, especially further s / se with temperatures into the mid / upper 20's celsius and increasingly fine..more like summer!!!!!!!..indeed, if I was in the SE I would be delighted with this run as it shows plenty of very warm weather later in the run!!!

Edited August 19, 2019 by JON SNOW

[Methuselah]

GEFS 00Zs stil look a tad messy...?

   

   

So a very uncertain outlook...

[knocker]

On it's own this EPS mean for Saturday is meaningless but it might be interesting to look at the clusters later.

Edited August 19, 2019 by knocker

[Frosty.]

Essentially / in a nutshell the Ecm 0z ensemble mean is indicating a north / south split with the north generally staying changeable / unsettled and cooler whereas summer predominantly returns southern uk, especially southern / southeast england..those are only the broad brushstrokes, the finer detail is above my paygrade!

Edited August 19, 2019 by JON SNOW

[MP-R]

Looks like a standard ridge - trough - ridge - trough scenario beyond the weekend. Fairly standard for the time of year, and more likely to transpire than a lengthy settled spell in my opinion. Also of note is that the troughs are swinging down from the northwest with ridges building behind, so perhaps temperatures a little below average if this is case as we enter September.

In the short term however, drying out a bit for many after today's showers (which are giving my location a thorough soaking at the moment). A brief blip of warmth on Friday and Saturday before something a little less settled from Sunday.

[Methuselah]

Not too bad a weekend in store, going by the 06Z; though, with PV-formation, the Atlantic hurricane season and ENSO all uncertain just now, who knows exactly what's about to transpire, in the longer term?

   

[Frosty.]

The Gem 0z shows what is essentially a north (nw) / south (se) split, for southern uk in particular it shows a change to predominantly summery weather with plenty of high pressure / strong ridging and warmth, by T+240 it's looking great further south and perhaps more generally across most of the uk going forward.

 

Edited August 19, 2019 by JON SNOW

[Methuselah]

The GEFS 06Z ensembles are still in a state of confusion, over where things are going. I think I prefer the ECM!

   

   

And, I am not liking those temps, going into early September either. I'm not liking them, one little bit!

[MATTWOLVES 3]

Looking at the big day next week, icon and ECM have a deep low pressure to our W/NW. The icon having it close enough to ruin things in the NW! Both GFS and GEM have high pressure gaining more influence... Still not sure how things are gonna pan out... NW/SE split looks the obvious more sensible call at this stage.... Regardless of what happens, it surely can't be any worse than today.... Downpour after Downpour here... Absolutely ferocious showers!! 

[knocker]

The clusters merely emphasize that a N/S split over Saturday and Sunday is the percentage play before perhaps some more amplification

 

Edited August 19, 2019 by knocker

[knocker]

Sat image 1345 UTC

[knocker]

A much more watered down trough Sat/Sun from the gfs before the high starts to ridge NE on Monday. So mainly dry apart from some showery activity in the north and temps pretty respectable

 

 

[knocker]

And the 5-10 anomaly has a familiar look to it with twin flows around the Labrador block and a fairly strong upper westerly flow across the Atlantic with some influence from the subtropical high pressure

[Captain Shortwave]

A long way off, but there does seem to be a disturbance that could bring thundery downpours on Sunday. Saturday looks foods, or at least for eastern areas at least. It does look like a warm weekend though with the ECM looking the warmest with 850s above 15c by Sunday.

[knocker]

The ecm also has weak deconstructing trough over Sat/Sun whilst another intense upper low drops into the Atlantic that drifts slowly towards Iceland. Thus the UK pretty much in a col and mainly dry albeit some frontal rain does effect the north west on Monday. But the detail still awaits sorting

But given the lack of interest in the thread there doesn't seem much point in making the effort tp post anything

Edited August 19, 2019 by knocker

[Methuselah]

A very entropic picture being painted by the GEFS 12Z ensembles:

   

   

I'd say that FI starts as early as Day 6...?

[Downpour]

4 hours ago, knocker said:

Sat image 1345 UTC

 

2 hours ago, knocker said:

A much more watered down trough Sat/Sun from the gfs before the high starts to ridge NE on Monday. So mainly dry apart from some showery activity in the north and temps pretty respectable

 

 

Yes good shout on this earlier. It didn’t look plausible and you nailed it. Bank hol weekend looking pretty decent with the Saturday probably the best day of the three. 

[Mike Poole]

Models at T144:

So, increasingly settled until the weekend and then what?  Whether a trough, a col or not much impact is still uncertain, with GFS legacy the most settled, JMA and UKMO putting more of a thorn in the side of decent weather.  Still a lot to resolve at 6 days time.