Model output discussion - hot spell beckons but then what?

[Methuselah]

Nae withstanding its 'less straightforward' ushering-in of warmer, sunnier conditions, generally, the GFS 00Z has us firmly ensconced on the southern side of the jet. Always a god thing?

   

And the GEFS ensembles reflect that, with T850s mostly between 5 and 10C:

   

And, consequently, maxes lying largely in the range 20 to 25C:

   

It all looks pretty darn good to me!

[knocker]

Although the EPS medium term anomaly is looking at a more fluid Atlantic with a westerly upper flow around a weak ridge/trough combination, the flow is not strong and positive anomalies cover the Atlantic so nothing particularly drastic and one would expect a fair amount of influence from the subtropical high centered away to the south west and thus a relatively dry period with temps perhaps nudging a tad above average

Edited August 16, 2019 by knocker

[Guest]

Ugh, big old watering down of the settled and warm end to August, looks like an upper trough could get anchored over the UK and really anything more than the odd decent looking unlikely in the reliable time frame. BH weekend could be a stinker if that low get wedged between high pressure to our west and east!!

[Frosty.]

The GEFS 0z mean in the mid / longer term looks very similar to yesterday, no downgrade, at worst it's a north / south split with plenty of azores high / ridge influence for southern uk once this very unsettled autumnal spell ends early next week..gradual improvement next week, mainly for the south...likewise the Ecm 0z ensemble mean, becoming predominantly much better for the south with increasing ridging, and pleasantly warm.

Edited August 16, 2019 by Jon Snow

[mb018538]

ECM op this morning was a cool and unsettled outlier - thankfully. Still not looking as promising as it was 1-2 days ago as low pressure has more influence than previously thought.

[MATTWOLVES 3]

I feel a little uncertainty creeping in on here today!! With Bank Holiday approaching, it's to be expected.. It's a much better ECM mean than the op though... Obviously it could still all go wrong, but has it stands... Not to bad. 

[Singularity]

 

On seeing the additional trough disruption in the 00z runs, I thought 'fair enough that it exists, but surely not that far east?'.

The 06z FV3 has adjusted west, which I agree with, but hasn't disrupted the trough as much, so it doesn't show the possibility that arose in my mind for a very warm feed from the southeast to feature next weekend, ahead of a Scandinavian High taking over proceedings.

Looks like we'll instead see the 'ridge exchange' solution that was dominant yesterday for the 10-14 day period; a new ridge pushing across quickly from the southwest, with a brief incursion of cooler air.

 

Before all that, the settling down day for the south has firmed up as Tue 20th, while it remains less clear for the north - anywhere between 21st and 23rd and that's assuming the 00z FV3 and ECM runs were wayward with their sliding of a trough southeast through the UK.

I've long been focusing on this settling down, as the autumnal near-term is being well covered by Knocker especially, and to be frank, it doesn't interest me much at this time of year unless the winds are exceptionally strong, which isn't expected this time around (though I will concede that widespread 30-40 mph gusts is not standard fayre).

[Summer Sun]

UKMO extended keeps the high going through to D7 

[MATTWOLVES 3]

Just to show how these models have completely different ideas at day 10...just look at the 0z and 6z at day 10....yes a long way off... But quite some discrepancies either way! 

[mushymanrob]

14 hours ago, knocker said:

There appears to be a lot going on upstream with tonight's outputs with intense Aleutian lows and TPV in the western Arctic resulting in the settled warm spell not looking quite so nailed on this evening. There is no particular agreement with the anomalies but the GEFS and EPS have both backtracked This is not to say the weather will not show a marked improvement and at the moment merely something to keep an eye on

 

yep, thats one thing thats bothered me, ( going off the noaa charts alone ), whilst they suggest a +ive pressure rise, they still are not on board for a large strong anticyclone that a lot of op runs have been (and still are) suggesting. the main event now is suggested just fter the bank holiday.

[Methuselah]

A not entirely unexpected hint of HP out west, on today's 06Z...I wonder if it could be a NWPM's overreaction to an NWPM-predicted (or actual?) uptick in easterly trade winds, in the Pacific?

   

PS: I'm still a beginner!

[78/79]

4 hours ago, Ed Stone said:

Nae withstanding its 'less straightforward' ushering-in of warmer, sunnier conditions, generally, the GFS 00Z has us firmly ensconced on the southern side of the jet. Always a god thing?

   

And the GEFS ensembles reflect that, with T850s mostly between 5 and 10C:

   

And, consequently, maxes lying largely in the range 20 to 25C:

   

It all looks pretty darn good to me!

A bit of divine intervention works every time Ed 

[Methuselah]

The 06Z ensembles are also okay.

   

   

Some very nice maxes in there...

[Panayiotis]

2 hours ago, Mattwolves said:

Just to show how these models have completely different ideas at day 10...just look at the 0z and 6z at day 10....yes a long way off... But quite some discrepancies either way! 

Key thing to note is:

Lower heights to the north + low pressure near Iceland 

Azores high edging NE towards the UK

Big Russian high 

UK weather will flop flop every run but at least the gfs isn’t showing a zonal pattern with low pressure systems hitting the UK

Edited August 16, 2019 by Panayiotis

[Frosty.]

Looking at the GEFS 6z there's a high chance of high pressure dominating towards the end of august, the signal strengthens longer term. As for next week it's an improving picture compared to this week, especially southern uk with ridge replacing ridge further south.

[MATTWOLVES 3]

Looking at the extended ecm 0z ensembles out to the end of the month.... Sea level pressure coming in at 1020mb,so definitely signs of some settled conditions.... Caution, a fair amount of scatter!! The temperature mean is not suggestive of a major warm up either.... This would do me and a fair few others fine!! Low 20s and relatively cool nights could be a decent call.... Beyond that who knows!!! And hey ho, give me another month and I will be close to getting my winter head on.... 

[Tamara]

On 10/08/2019 at 16:04, Tamara said:

As previously alluded to the unassuming neutral status disguises some stark contrasts in SST's across the Pacific which looks set to throw curveballs to modelling now and through into the autumn itself.

Another self quote - just for the purposes of continuing thought relevance to the way ahead.

The much recently discussed mercurial set-up in the Pacific, at a time when the first hints of seasonal change are starting to appear within an unstably punch drunk arctic profile - are manifesting themselves through inchoate, and somewhat capricious numerical modelling in terms of energy flow and distribution.

Endless repetition of not taking NWP at face value, and not reacting too much into each and every operational output, is admittedly a broken and probably annoying record, but with NWP caution in mind, the ensembles continue to persist, overall, with the idea of anomalous mid latitude ridging, ebbing and flowing, and consistent with the overall volatile mix and duelling of low frequency signal vs intermittent -ve wind anomalies in the EPAC.

The danger, and I have seen this in some social media weather pattern commentary, is taking these countervailing wind-flows in isolation and trying to fit individual numerical modelling solutions to them that (appear) to most closely identify - and presenting a rolling 'forecast' forward based on attempted coefficient x+y assumptions about how strong each of the variables present are - when each variable is in reality, the sum of all parts and not compartmentalized in isolation.

This is very much an especially blended diagnostic outlook and one where the blended solution in the numerical models is, equally, therefore the most sensible way forward at times like these

Overall, with a slight erring to relative angular momentum being fractionally weaker than optimally desired for very best ridging profile for warmth and most settled conditions nationwide -

- those percentages support the idea of mid latitude ridging slightly to the west of the UK and with  a little more +ve momentum in the polar jet than would be preferred for that greater nationwide settled potential. The sub tropical ridge ebbing and flowing with the westerly upper flow and steering systems downstream close to Iceland

The more downside to AAM, then the greater chance of ridging retracting and greater trough disruption. Up to now, this has been perceived as reasonably contained and not sustainable.

However, its worth a bit of additional perspective here -

Much has been spoken of the low frequency signal and the ally of having an oceanic SST configuration to assist a convergence zone .

 

However, in the light of the persistent -ve zonal wind anomalies in the EPAC, the time is coming where support is increasingly required from the high frequency MJO signal to provide a big additional spike in westerly wind additions to properly combat the EPAC trade winds, ramp up angular momentum on a more substantial level, and in turn prevent the Pacific from more widespread cooling that would diminish the tropical convergence in the Pacific and which would have some ramifications to blend with other intra seasonal factors that evolve, for many weeks ahead (and right through the autumn and possibly beyond).

The MJO itself has been quiet for some weeks and this has had some influence in supressing the upside to angular momentum, despite the weak walker cell producing a modest supply of westerly winds in the CPAC to counter balance the EPAC trade winds.

As stated in the previous post, the MJO is only a part story to the whole GSDM budget. But it often is, nevertheless, a major catalyst to shaking up the atmospheric circulation and forcing pattern change at the synoptic level. Interest in this intra seasonal cyclical tropical wave phenomenon tends to be restricted to the winter, due to being ( totally erroneously) perceived soley as a magic bullet to deliver cold spells and of no significance or importance at any other time of year.. However, its influences wax and wane all year around and it can have significance for weather patterns equally all year (and not necessarily always to fit human weather preferences)

In the here and now, the longer that the high frequency tropical convection signal stays quiet, then the tendency for more sustained falls in angular momentum grows, as easterly wind inertia is allowed to spread from the tropics to wider areas of the extra tropics. This would be reflected in the Global Wind Oscillation incrementally orbiting further towards the La Nina attractor phases -

,

 - and in tandem with seasonal wavelength changes, increase the chances of atlantic ridging taking up residence too far to our west to influence better weather - and inviting a longer lasting trough signal.

This doesn't mean automatically mean a La Nina base state would be arriving  It simply refers to a somewhat a-typical relationship that the atmospheric circulation would adopt to the (neutral) base state at such a given time (if such a circumstance evolved)

Based on intra-seasonal factors (and related to the end of the Indian Monsoon summer cycle) the high frequency signal may well pep up once again over the coming weeks, but hopes of late seasonal warmth and an Indian summer for those like me who would highly welcome it, will more and more rest on this type of eventuality

.

 

 

 

 

[knocker]

H/t Simon Lee (it's certainly been wet in these parts today)

An unseasonably deep (978 hPa at 06Z) cyclone NW of the British Isles is associated with an atmospheric river bringing deep subtropical moisture. 00Z sounding from Valentia, Ireland had 40 mm precipitable water with 562 dam thickness!

 

[knocker]

More promising from the gfs vis the holiday weekend (at the moment)

The Atlantic trough is disrupted Friday/Sat as the European subtropical high amplifies which facilitates north east ridging from it's Atlantic counterpart

 

[Mike Storm]

Yes please 

[Methuselah]

The end of the 12Z run/ensembles looks as good as the 06Zs looked (almost) bad. I think it's fair to say that the question of which centre of HP, if either, will dominate is far from settled?

   

   

   

The outlook could be far worse!

 

 

 

[I remember Atlantic 252]

EC looks good! after 00Z looked vile at this range

[mb018538]

Gfs has totally gone off on one tonight, ecm looks ok...probably end up somewhere in between. A lot of sorting out to still be done.

[Dangerous55019]

Evening everyone. 
Thought I'd throw in what the CFS V2 is forecasting, and see if this can shed a bit of light on the upcoming 'settled' spell.

Week one shows us a trough of low pressure anchored just off the North West of Scotland, so I would imagine that being a continuation of this current unsettled/autumnal spell of weather. 
Week two however (which takes us pretty much through to the end of August) shows us here in the UK under a rather large ridge of high pressure, and I would say looking at it, that it could fetch us warm easterly winds! So if you're after a late burst of summer... This does look very promising indeed! 
And then weeks three and four, from the very end of August through to the 12th of September... One word... Plumey!!! Now as someone who enjoys thunderstorms, this has really gotten my interest! Two weeks worth of Spanish Plume(s)? Yes please!!  

As ever this is the CFS V2, so please take it with a gritter load of salt, but hey, lets see what happens. 



 

[knocker]

The ecm shows what a difference in emphasis from the subtropical zones can make in 12 hours Still a lot to be sorted later next week