Model Output Discussions 12z 01/06/2017

[Man With Beard]

Something interesting has popped up on the Icelandic Met weather model repository (brunnur.vedur.is). My Icelandic is a bit rusty  but I'm guessing these are ECM ensemble clusters?

        

CR must mean the cluster with the control run, and OP must mean the cluster with the operational run. The charts at the bottom seem more for general guidance rather than being part of the modelling.

If I'm right, I'm pleased to see there are at least some clusters that provide long term hope!! Cluster 2 at T360 looks particularly fantastic!!

Oh, the straws me and Frosty will be able to clutch now...!!!  

[DR(S)NO]

35 minutes ago, Sky Full said:

What are the chances - eight days of unrelenting low pressure right over the UK at the height of summer....

Just when you think it might move away to the east, another one comes rolling in to keep it going.   This continues even into far FI so unless something changes dramatically the first part of the summer holidays will see frequent showers and annoyingly strong westerlies nearly everywhere.  Could be worse though - at least it won't be overly cold.  I am looking out for signs of this pattern changing though - the last two warm and sunny spells were not properly foreseen by the models until five days out so they can't be relied on to have the next ten days nailed on......

 

 

The AH just does not want to ridge in.....pretty sure that's another low waiting in the wings ready to zip along for the 4th/5th....

 

[Frosty.]

Good news from today's update which is an upgrade on recent days and indicates increasing signs of high pressure and rising temperatures, at least for southern uk not far into august and the GEFS 6z mean also shows signs of the Azores high ridging towards southern uk during the same period. In the meantime it looks like staying generally unsettled but tending to be coolest and windiest across north-west uk..and then hopefully becoming more settled and warmer from the south as we go further into august.

[Singularity]

Well, the main component responsible for our descent into some kind of hell is has weakened and looks less coherent over the next week or so - but it seems there is too much lagged response still feeding through to put the brakes on that next low making its way across the N. Atlantic early next week.

I say seems because there's inevitably at least some chance the models are overdoing the longevity and/or strength of response. 

If that low does make it across it will represent an extraordinary sequence even under La Nina-like forcing. Helped into reality by the unusual N. Atlantic SST patterns and perhaps a dose of low Arctic sea ice forcing too which seems to encourage some extra southward deviation of the jet stream even when it's fairly strong - although that last link is still debatable due to a lack of observed cases (less than a decade of years sea ice extent on a par with what we have now - but among the closest are 2007, 2011 and 2012... which all had another thing in common! The other two are 2010 and 2016 which weren't so bad but the latter still had its issues as I'm sure we can remember - just not in the same half of the summer).

Given the predicted easing of C. Pacific trades and the MJO making some eastward progress from the Indian Ocean, our chances of breaking free from this pattern do look much better by some 4-8 days into August - but this depends on those trades not revamping against the model expectations which I do have to wonder about given the tendency of the past month or so.

[Frosty.]

Another upgrade, the GEFS 12z mean shows stronger support than the 6z for the Azores high to build in during the period between early and mid august..I'm just trying to bring some hope that august won't be a cool unsettled write off!..I don't think it will be! to me there are signs that we will see some warm anticyclonic conditions during august, especially further south. 

Edited July 26, 2017 by Frosty.

[phil nw.]

We can only hope for some improvement to this unsettled pattern later into next month.

Certainly for the next few days it continues to look very unsettled and cyclonic with bands of rain or showers nationwide.

A couple of fax charts underline the poor outlook

A look at the expected Northern Hemisphere at day 5 shows how far south the jet path is modeled,down into mid-latitudes

Sub-tropical high cells around the hemisphere looking very suppressed and our own Azores high very much held away from it's normal position.Instead we see +ve Greenland height anomalies pushing the jet further south.

Sorry to sound downbeat but it is what it is,one of the worst patterns for our so called high Summer with Atlantic systems being routed our way,

It really is a matter of making the best out of any brighter interludes that may come between the unsettled spells.  

 

[Frosty.]

For the most part, northern UK has the worst of the cool and unsettled conditions on the Ecm 12z as they are closest to the trough apart from next midweek when a deepening depression zips in from the atlantic bringing a spell of wet and windy weather to all areas. Towards the end of the run a ridge of high pressure builds in across southern UK with a spell of fine and pleasantly warm weather. The general set up in the coming days is sunshine and showers, some heavy with hail and thunder and merging at times to give longer periods of rain with the windiest and coolest weather across n.ireland and western scotland, away from the showers further south / south-east it will feel warm in the sunshine and generally lighter winds..it's certainly not all bad!

Edited July 26, 2017 by Frosty.

[knocker]

A quick look at the ecm this evening.

Friday 1800 sees the main low west of the Hebrides and a quite wet, showery period affecting Scotland, and a shortwave that has formed way the south west and has tracked very rapidly ENE, just impacting Cornwall. This tracks rapidly through and the next one quickly arrives in the Channel to bring some wet weather to the south in the early hours of Sunday. This too quickly moves east and by 12 Sunday low pressure covers the UK and thus cool showery weather.

Over the next couple of days the low fills and drifts north of Scotland so showers become less frequent as the Azores attempts to nudge NE into England but by 12z Wednesday the next Atlantic depression has arrived west of southern Ireland with associated fronts Ireland/Cornwall/NW of Coruna This low then tracks east across the UK initiating a very and windy couple of days.

And the 850mb temp and contours

 

Edited July 26, 2017 by knocker

[Man With Beard]

This evening's ECM at T240 represented the least populated cluster from this mornings 00Z ensembles (12 out of 51 members) - see my post above. The other 39 runs were far less settled

[damianslaw]

Models painting a very unsettled 'unsummery' type pattern for the foreseeable, positive height anomalies to the NW, a very southerly strong jetstream, the UK locked on the colder side (not often we have experienced this over the past 12 months), with low pressure really becoming unstuck to the NW, propped up by secondary low/trough action from the SW, once we lose the current low, which is set to stay static in situ until Monday - that's 5 days!, we see another low pressure quickly takes it place albeit slightly further west in position. This is a poor outlook for high summer, with temps and sunshine levels very suppressed, conversely some high rainfall totals for some..

Longer term - well we have the start of the influence of the hurricane season, and there are signals of tropical storm developments over the Pacific perhaps impacting on us as we run through the early part of August, which might have the effect of unbuckling the jetstream.. we shall see.

Lets hope we don't have to endure yet again a rather poor August, only for the high pressure and settled conditions to return in time for September and the end of the school holidays.. as seems to have been the case for a good well 13 years now..at least around here. 

[Man With Beard]

On tonight's ECM ensemble clusters, 26 out of 52 members maintain trough dominance over the UK at D10, 14 runs follow the op with a rather more changeable pattern and 11 build a block very close by to the west. So rather unclear where we're headed from that. Between D11-D15, clusters generally improve but no clear cut picture

[knocker]

Last evening's anomalies, although not showing significant changes in the upper pattern were, perhaps moving in the right direction. The influential upper low has drifted north of the UK and is filling, eventually to lose it's identity as it moves east. Thus for a time the more unsettled weather may well be more to the south of the country as systems swing through on the quite strong upper westerlies.But hopefully, and there have been some indications of this recently in the later period, With the trough no longer on the scene the Azores can push north in the Atlantic thus veering the upper flow portending some drier and more settled weather, albeit with the usual geographic bias.

Meanwhile back on the farm and after a quick look at this morning's gfs I felt, as Yogi Berra once said, it was deja vu all over again. We are currently struggling to get rid of one upper low and eventually after we do the same sequence may well run again next week.

Anyway I suspect everyone is familiar with the prospects for the next four days with the low parked to the north west. Essentially the UK will be in a showery westerly airstream with occasional periods of more concentrated rain as systems run in from the southern quadrant of the main low. But all the time the low is slowly filling and by 00 Tuesday it has virtually lost it's identity

High pressure then pushes in from the south but the aforementioned next intense upper low is en route which manages to distort the jet and thus by 12z Wednesday the large surface low 980mb dominates the eastern Atlantic with the associated fronts over Ireland.

From here the low drifts NNE and the fronts traverse the country and another westerly showery regime is the order of the day but really no point in going into detail because so much is dependent on how precisely  this pans out, if it does of course.

 

Edited July 27, 2017 by knocker

[knocker]

The general theme of the ecm is not a million miles away from the gfs

[mb018538]

Some signals again in the latter half of the GFS that things could settle down a bit after the first weekend in August. Much will depend on all of those systems in the Pacific hopefully buckling  the jetstream and shaking us out of the zonal flow. Hard to predict their effect at the moment, but it looks like our best bet of a get out of jail free card.

[draztik]

28 minutes ago, mb018538 said:

Some signals again in the latter half of the GFS that things could settle down a bit after the first weekend in August. Much will depend on all of those systems in the Pacific hopefully buckling  the jetstream and shaking us out of the zonal flow. Hard to predict their effect at the moment, but it looks like our best bet of a get out of jail free card.

Given the outlook, we may have to trade Mayfair & Park Lane for that get out of jail card! 

[Man With Beard]

In the midst of generally unsettled charts, there are some positives. Firstly, that midweek "break" from the low pressure train looks well and truly on, and all areas could have a proper summer's day on Wednesday (SE areas may get lucky and have three good days)

       

The 850hpa charts showing the chance of much higher temperatures for a couple of days in most areas (the ECM not quite as warm but certainly warmer than it will be over the next few days)

Secondly, the D9/D10 charts coming in are starting to look more positive too. The jet is slowing, op runs continue to weaken the Greenland block (with the ECM mean now looking less blocked over Greenland by D10 compared with yesterday, too - while the GEFS is now more blocked at this timeframe), and the track of the Atlantic storms looks to be less intense and lifted a touch north. Of course, great caution needed at such a long range, ensemble support isn't rock solid for a change and some runs such as the ECM op at T240 look like the trough could get reinforced fairly quickly. But reason to hope for some better weather in the second week of August.

       

[Singularity]

 

That sharpening of the trough (increased southward extension with little change in west-east span of trough) is the best straw we've had to clutch in quite a while 

GFS is the most enthusiastic of the operational runs this morning so once again we're looking at a less generous ECM run and willing it to play nice for a change .

Good to see some shift in the respective ensemble suites for the two models though. 

GLAAM is on another upward trend - exceeding that depicted by recent modelling from GEFS, and despite an apparent stall in the MJO propagation yesterday the models became more keen on further progress east toward the C-Pacific where an associated westerly wind burst should be able to weaken (or with any luck cancel out) those anomalously strong easterly trades. 

Maybe there is some chance that short-term underestimation of GLAAM could nudge things far enough in favour of subtropical ridge extension through Europe to encourage the sharper, stalling trough scenario for mid-next week, but the greater impetus toward an improving picture still looks most likely to set in nearer next weekend (by the start of it, with a bit of luck). Again with the usual caveats regarding those pesky trade winds.

[summer blizzard]

It's probably also worth adding that there is a monster of a Kelvin Wave crossing the Atlantic in early August. This may suggest a period of tropical storm/hurricane formation so watch for those systems to start playing with the models. 

[Singularity]

Good spot @summer blizzard, tense times for Caribbean-N. American residents/tourists given a lot of other parameters supporting a high frequency and potential intensity of cyclones this season, and who's betting it'll make a hash of an otherwise improving picture in our little slice of the hemisphere 

[Man With Beard]

ECM 00Z clusters report: 27 out of 51 ECM ensemble members are in the same cluster the op run at T144, and 17 more members are in a similar looking cluster, so fair confidence that the short midweek warm-up is reliable (though interestingly this cluster is unlike any other cluster from the past four days for this timeframe!).

By T240, the op run is in the smallest cluster, supported by only 6 out of 51 members, and it is the only cluster that has another deep low heading our way. The other clusters are equally split between an emphasis on a Scandinavian trough (24 members), and another cluster (which contains the control run) that flattens the 500mb flow with no major trough formation close by (21 members). So although the T240 mean chart shows a Scandi/North Sea trough, more than 50% of ensemble members don't actually make much of one.

Into T264-T360, 20 members are in a cluster that maintains a Scandinavian trough, which transfers back to the UK with time along with a fairly blocked Atlantic. 19 members are in the control run cluster, which has a better tendency for ridging through the UK interrupted by occasional Atlantic depressions that are weaker and further north than of late. 12 members have a more sustained attempt at building a ridge across the UK, keeping troughs more generally to the north.

Perhaps I could have summarised the T192-T360 period more simply: a bit better, but no clear way forward!

[Frosty.]

I like the new upgrade..i also like the Gfs 6z in low res as high pressure builds in with settled and warm weather across the UK.

[Britneyfan]

I'm liking the look of the weather in the south east next week! We could get 25 degrees! Only a small shower risk! 

Hopefully that better weather will spread northwards, where it looks to be cooler with the higher risk of rain or showers!

but the overall trend does not seem a bad as it once was perhaps 

[stodge]

Afternoon all

Let's be clear though - any "hope" from the GFS 06Z OP is in low-res with a brief settling in the south at the end of the first week in August and, after a brief hiatus, a more sustained pressure rise for part of the second week before another breakdown at the end of FI.

It's low-res, it's FI, it's transitory.

That being said, it's the crumbs from the table but it'll be interesting to see if this a) becomes a trend and b) is reflected in the Ensembles for 06Z let alone later runs.

For now, it's not exactly grim but it's not exactly great.

 

 

[claret047]

4 hours ago, summer blizzard said:

It's probably also worth adding that there is a monster of a Kelvin Wave crossing the Atlantic in early August. This may suggest a period of tropical storm/hurricane formation so watch for those systems to start playing with the models. 

Hello Summer Blizzard,

I trust you are well.

Being less well versed in weather matters than your goodself, may I ask in what way do you see this panning out. Do you for example see more ridges thrown up in the Atlantic or any attempts at these building being pushed aside by depressions being pushed through at speed on a strong jet stream directly over us.

Kind Regards

Dave

[Gael_Force]

JMA update not seeing much change through August.

http://ds.data.jma.go.jp/gmd/tcc/tcc/products/model/map/1mE/map1/pztmap.php

Need to look to the tropics for a kick to the pattern.