Model output discussion 14/04/18

[mb018538]

The other thing to note is that a lot of Europe has been above average temps wise in recent weeks....good omen for summer? Certainly a very different set of building blocks this year since the SSW throw the atmosphere into chaos.

[weatherguru14]

4 hours ago, I remember Atlantic 252 said:

my imagination or does Friday look yucky? 6Z showed it too

I take this chart with a pinch of salt.. for years its  done this.  100000c in france and just over the channel we struggle to get into double  figures.

[northwestsnow]

More glorious charts this morning ..

Warm and dry this week with isolated storms and its looking like we may see a plume longer term, well according to GFS that is.

[East_England_Stormchaser91]

In a nutshell for this morning, if an endless plume is not your thing, Look away now! 

Absolute convective paradise for the storm lovers, pretty much right throughout the entire run. What a year this could be shaping up to be, both for coldies earlier in March and for the thunderheads! Or even better if you’re like me and do both! 

[Scorcher]

50 minutes ago, northwestsnow said:

More glorious charts this morning ..

Warm and dry this week with isolated storms and its looking like we may see a plume longer term, well according to GFS that is.

Yes the longevity of the settled conditions looks quite staggering...hard to see where a breakdown will come from!

It's almost inevitable that the progression into next weekend will lead to some sort of plume scenario. 

[mb018538]

This mornings runs....WOW!!

Growing support for a plume into the bank holiday. I mean look at this ridiculous ECM 168 chart today:

http://www.meteociel.fr/modeles/ecmwf/runs/2018052100/ECM0-168.GIF?21-12

Nearly the entire UK bathed in +12c uppers, touching +14c in places. Unreal for late May, and could be the third very hot spell of weather for 2018 already, and we're not even in the summer months yet. Superb.

[mb018538]

Staggering ensemble too:

http://www.theweatheroutlook.com/charts/gefs/gefsens850london0.png

Mean touching 10c for a good number of days.

[h2005__uk__]

59 minutes ago, mb018538 said:

Nearly the entire UK bathed in +12c uppers, touching +14c in places. Unreal for late May, and could be the third very hot spell of weather for 2018 already, and we're not even in the summer months yet. Superb.

What sort of ground temps would those uppers give at this time of year?

[mb018538]

8 minutes ago, h2005__uk__ said:

What sort of ground temps would those uppers give at this time of year?

All very up in the air....if it verified as shown you could probably expect somewhere to top 30c *if* it stayed sunny. A long way off at present, but one to certainly keep tabs on.  

[MP-R]

19 minutes ago, mb018538 said:

All very up in the air....if it verified as shown you could probably expect somewhere to top 30c *if* it stayed sunny. A long way off at present, but one to certainly keep tabs on.  

Increasingly dry ground will also help temperatures be that little bit higher. The hot blip in late May 2010 was a good example.

[Guest]

11 hours ago, weatherguru14 said:

I take this chart with a pinch of salt.. for years its  done this.  100000c in france and just over the channel we struggle to get into double  figures.

Problem is the source wind direction, same for Saturday. Warmer, moister air advected north over central Europe and then westwards over the north sea would deliver a complete clag-fest for the south half of the UK, while 20 miles across the channel temps would be in the high twenties in glorious sunshine.

Edited May 21, 2018 by Alderc

[Guest]

46 minutes ago, h2005__uk__ said:

What sort of ground temps would those uppers give at this time of year?

 Depending on wind and cloud conditions London would get close to 30C in unbroken sunshine. 25-28C elsewhere in the south.

[fujita5]

Just now, Alderc said:

Problem is though is the source wind direction, same for Saturday. Warmer, moister air advected north over central Europe and then westwards over the north sea would deliver a complete clag-fest for the south half of the UK, while 20 miles across the channel temps would be in the high twenties in glorious sunshine.

Yeah these types of days can be really frustrating.  Every now and then you get a slight thinning of the cloud and it's *boiling* for 30 seconds then it's gone.  Although once I did see a huge mid level MCS drift E>W just to my south with a complete clearance of the low cloud.  Nice lightning show then back to clag!

[Man With Beard]

2 hours ago, mb018538 said:

This mornings runs....WOW!!

Growing support for a plume into the bank holiday. I mean look at this ridiculous ECM 168 chart today:

http://www.meteociel.fr/modeles/ecmwf/runs/2018052100/ECM0-168.GIF?21-12

Nearly the entire UK bathed in +12c uppers, touching +14c in places. Unreal for late May, and could be the third very hot spell of weather for 2018 already, and we're not even in the summer months yet. Superb.

ECM temperature charts on weather.us raw data shows 28C for both Sunday and Bank Holiday Monday - however, the model seems to underdo the extremes of heat, so I'd say 30/31C is well in the game on this morning's chart.

Most models do seem to have upped the convection over southern areas for the next 7 days. This is the GFS by Friday:

ARPEGE is not too different. (Most rain in the north falls in the next 24 hours btw so Scottish sun seekers need not be too alarmed!)

So not wall-to-wall sunshine by any means. It's going to be a real mix - periods of clear blue sky and rocketing temperatures, and some periods of cloud and heavy rain. I'm guessing the sunny periods will be more than the cloudy ones, particularly further north, but it's always a tough game working out where continental convection will hit.

Into next weekend and it's not only some spectacular heat to watch out for in the south, but quite possibly some spectacular storms too. GFS for Monday:

The ECM gets the action going even earlier, with severe thunderstorms on both Saturday and Sunday night.

Meanwhile, the north looks set to carry on serenely with sunny and warm conditions throughout.

So it's going to be a fascinating week, more like early August than late May

[stodge]

Morning all

Been away due to a family bereavement and haven't looked at a chart for 10 days or more. The last I remember was plenty of northern blocking building for later in May with heights to the north and persistent LP over Europe leading to an easterly flow and the risk of showers for southern and south western parts.

As a man from Sheffield once said "that was then, this is now". The medium term analysis goes out to Thursday May 31st and starts as always with the morning's ECM output at T+240:

Not a lot has changed. Heights over Scandinavia and a notable trough over Europe bring in a warm, if not very warm, SE'ly flow for many over the coming Bank Holiday but the HP retrogresses to Greenland meaning pressure drops near the British Isles and shallow Atlantic systems are edging in to the south west with a cooler NE'ly flow across the far north. Settled for now but the notion of things going downhill at speed is evident.

GEM 00Z OP at the same time:

Some differences to ECM. Good agreement through the weekend with the warm SE'ly but GEM takes the trough further north across the British Isles before heights rise again to the NW and NE and we end with a light easterly flow but still with a risk of showers for southern and south western areas.

GFS 00Z OP at T+240:

The HP doesn't retrogress as with ECM but moves back into Scandinavia and declines SE but the pressure gradient over the British Isles is very slack. Some residual LP to the south west but very much a holding pattern with showers possible but very light winds. Further into FI and HP builds to the north and north west so another dose of easterly winds before a trough develops over Scandinavia and extends SW bringing in cooler and more changeable conditions.

GFS Parallel at the same time:

Again, a very slack evolution with a shallow trough over the southern North Sea so showers or thunderstorms possible in southern and eastern areas. Further into FI and a strong ridge develops NE from the Azores into June keeping the weather fine and warm for most.

GFS Control at the same time;

Heights to the NE remains strong but the European LP has moved up into southern areas bringing in an enhanced risk of showers or storms. Further into FI and the HP and the continental LP re-orient to bring in a cooler ENE'ly flow with showers still a risk in the south.

IN summary, a fine and very warm Bank Holiday weekend for many albeit with a growing risk of showers or storms for the south and south west. Into next week and a range of options on offer - ECM offers retrogression but the percentage call looks to be a slack flow which would be reasonable for most but if you do get a shower or storm it would be very slow moving and consequently could drop a lot of rain on a localised area. Absolutely no sign of Atlantic influence and while Parallel offers a nice continuation of the fine spell into June via an Azores ridge other options maintain the pattern of heights to the north and lower pressure over Europe periodically extending across southern parts of the British Isles. 

 

 

[mushymanrob]

sorry chaps, whilst there are some stunning outputs currently if you like it hot, the anomaly charts dont agree with the ops as to where the high will be centered, and the anomaly charts are more often then not correct. they have been suggesting high pressure evolution just west of north now for several days which to me suggests consistency.
so to my eye, this chart


will not lead to this

[mb018538]

44 minutes ago, mushymanrob said:

sorry chaps, whilst there are some stunning outputs currently if you like it hot, the anomaly charts dont agree with the ops as to where the high will be centered, and the anomaly charts are more often then not correct. they have been suggesting high pressure evolution just west of north now for several days which to me suggests consistency.
so to my eye, this chart


will not lead to this

That's a fair point. Just one to keep an eye on - perhaps the OPs have been teasing us!

The 6z is plume-tastic too for what its worth. Everything is going to hinge on the disturbance over Iberia in the next week, which will aid the advection of all this warm/hot air our way (if it materialises).

[Djdazzle]

The anomaly charts have been wrong on numerous occasions. Not saying they are, but if all of the op runs contradict it, I wouldn’t be backing over them.

I have seen anomaly charts showing a black hole over Greenland at 7 days, only for them to be wrong.

[h2005__uk__]

1 hour ago, Man With Beard said:

ECM temperature charts on weather.us raw data shows 28C for both Sunday and Bank Holiday Monday - however, the model seems to underdo the extremes of heat, so I'd say 30/31C is well in the game on this morning's chart.

Do you have a link to that please? I can't seem to find ground temps for ECM.

[Man With Beard]

Regarding the D11-D15 period, we're now at 50/50 in the EC clusters between retrogression to the NW and a continuing Sceuro ridge.

The trend is definitely on the up for "clear" retrogression; it was 15% yesterday morning, and 30% last night.

That said, I generally look for 2/3rds support for retrogression (so say 65/70%) before really latching onto it - it seems to be one of the patterns that most easily collapses closer to T0 these days. So it's still in the pending file, and I'm still extremely open to a continuation of the continental flow of this week even into June.

[Man With Beard]

3 minutes ago, h2005__uk__ said:

Do you have a link to that please? I can't seem to find ground temps for ECM.

https://weather.us/model-charts/euro/great-britain/max-temperature-6h/20180527-1800z.html

zoom in on the darkest bits and you'll see they show 28C. Rare to see anything this high on ECM raw data output!

 

[mushymanrob]

dont get me wrong here guys, id love the ops to be correct as i love heat.

its true the anomaly charts can be wrong and i hope they are. but realistically they are usually near as damnit correct and are better at predicting the mean upper flow for the 6-14 day period then the ops are. dont know if hes still around as ive not been on, but John Holmes study into these charts some years ago proved this to be the case - when consistent. (for newer members).

i use them all the time now, and dont often view the ops, im not too bad at reading what conditions we are likely to get and this has proven very popular on a facebook page i broadcast to (by request). so  confidence at reading them is quite solid.

the chart i posted shows the anticyclone anchored just west of north to the uk. that wouldnt allow for the hot deep southeasterly the ops currently predict as they have the high anchored further east over northern europe/scandinavia.

but hey ho, its just an observation, my faith in the anomaly charts has been misplaced before, i hope it is this time! time will tell.

[Uncle_Barty]

Was it CFS showing a sharp breakdown at the start of June a short time ago?

I hope the anamoly charts are wrong, but......    year ending in 8......

[bluearmy]

Take care with that anomaly upper heights chart - its a five day average and the high heights push ne from the azores (hence the mean chart showing so far west) so plenty of opportunity for the surface ridge to settle in an advantageous place to advect a hot se flow for a couple days.

as MWB notes, the future remains threateningly retrogressive though still no analysis how sustained this could be, nor how far west the mean upper ridge settles.

[Tamara]

On ‎15‎/‎05‎/‎2018 at 15:15, Tamara said:

At the moment, being still in Spring, the significance of easterlies being added upstream amplifying the Pacific pattern and decelerating the jet downstream remains a benign enough one ( @Singularity analysis is very good here).

However, (assuming for just one moment the atmospheric circulation remains close to where we are at present in light of latest drop backwards) seasonal wavelength changes heading into the summer which is fast approaching increasingly suggest a retrogressive pull of the long wave pattern with the spectre of that Atlantic ridge and downstream trough returning if the ocean/atmosphere relationship cannot fully break down the legacy of the La Nina standing wave.

This (in this scenario) would mean that despite the ENSO regime "technically" returning more neutral in association with many forecasted expectations - there would still be a -ve adjustment/disconnect to the atmosphere which inclines the AAM budget within the atmosphere being pre-disposed towards greater easterly wind-flow inertia and hence high pressure in both the Pacific and Atlantic - rather than a longwave more Nino-ish pattern of, the reverse profile, of Pacific and Atlantic troughs and respective downstream ridges.

The trough in our locale under summer type +AAM/El Nino type forcing being repeatedly focussed/re-set to our west in the Atlantic and the ridges over Western Europe and Scandinavia.

There is of course every possibility that this latter hoped for scenario prevails to underpin some of the promising seasonal modelling indications. 

If we take a look at the above copied GWO spider graph of the on-going low AAM phase of the tropical/extra tropical cycle , the Phase 1,2 orbit of the GWO is thus discernibly shallower than that of 6 weeks back. This reflects the overall grip that La Nina has relaxed on the atmosphere - though clearly not yet gone completely.

Its important that we see a willingness of persisting MJO tropical activity supporting further bounces in +ve AAM anomaly wave trains, but more important still an eastward shift of the locale of this tropical activity from the Western Hemisphere

The first and most important thing to say is to enjoy the spoils of some excellent weather in the 7 to 10 day period.  After a warm week ahead, it could feel quite tropical by the Bank Holiday weekend with hot sunshine for many and some thundery downpours for some....then clearing to let hot sunshine out again. Rinse and repeat for a few days

The last post gave some background as to how the early season warm spells have evolved since mid April.

The highlighted sections of the above extracts from that post last week then went on to try to anticipate a likely crossroads ahead. This crossroads now broken down into basic suggested pathway scenarios :

Changing seasonal wavelengths from Spring to Summer > leading to either,

Low atmospheric angular momentum retrogression of the wavelength - North Atlantic/Greenland ridge and downstream trough

or,

High(er) angular momentum greater retention of downstream Scandinavian/European ridging and a troughing profile in the Atlantic to our west

or,  

There is actually a third scenario that involves a lapse around the 12 to 15 day period into the Option 1 but a bounce (and likely a sustained cyclical bounce) back to Option 2 thereafter.

That is I freely admit, covering all options *and sounding like a lot of back covering on her part*  but two things here:

The aim is, and has never been to give long range predictive forecasts - there are plenty of guru's around who like to do that anyway without adding any more. Secondly, the balance of factors, as I see them, are very finely balanced, so it seems eminently sensible to pitch any summary suggestions to embrace all the spectre of possibilities within that envelope.

So I have my own little ensemble suite most of the time, which seems to work for me anyway

Speaking of ensembles, NWP has indeed started to take the suggested pathways under the radar as we start the new week. The retrogression spectre started to appear in some low resolution GFS output late last week and now the EPS clusters have started to pick up on this signal.

However, the background signals in relation to the tropics, extra tropics and subsequent consequences for atmospheric angular momentum remain uncertain. Based on some more recent historical precedence (and also a seemingly increasingly inherent longer term climate trend, but that is not for this thread) it would be easy to see start of summer and yet another collapsing angular momentum regime as somewhat predictable with a string of summers in the last 10 yrs following this same pattern.... Spring warmth leading to another indifferent cool and damp summer....

But back to basics - where are we with things this since time last week?

GLAAM has slumped back below average, losing the gains of the recovery earned since mid April

 

However, as likely commented to be the case last week, relative angular momentum tendency has been holding higher again in the present low cycle ebb than the previous low tide marks in the global wind-flow cycles of mid March and then early April.

 

The inference of this, extrapolated longer term, is that the atmosphere is trying to resurrect itself longer term from the La Nina state that has, mostly, been in evidence for the last two years.

Convection in the tropics in reflection of this, is continuing to imprint the active periodicity (recurrence) cycle of the last 90 days. As bolded in the captioned post above, what is very important as we hit June is that we see clear signals that MJO forcing wants to embrace eastward shift to the Pacific as represented by an evolution to Phases 6,7 and 8.

This, as demonstration that the upcoming cycle represents a further move away from La Nina with accelerating westerly wind inertia in the atmospheric circulation sustaining the priming of downstream summer warm ridges rather than sustained lapse into downstream summer chilly trough.

The deterministic tropical convection forecasts have been proving, not unusually, a bit too progressive with trying to break down amplitude of the latest cycle.

 

There is a conceivable chance this time around that modelling may overcook -ve AAM downside, and hence any blocking in the North Atlantic and/or Greenland may be overblown.

Either that, or of it does verify, it does not sustain.

Just this side of the Spring/Summer wavelength changes, in the short term the recent fall back of AAM has done no harm at all. Indeed, the upstream deceleration of the jet has/is helping our downstream ridge hold sway with a moribund Atlantic. The deceleration and amplification of the jet upstream in the Pacific clearly represented here by the -ve mountain torque over Asia - with the consequent vacuum created to fill as momentum is lost from atmospheric wind-flows

Such a negative AAM regime, however, not recovering as we arrive at imminent changing seasonal wavelengths also assists further retrogression of the longwave pattern and is not desirable longer term. So its important that momentum upstream has some impetus heading into the new month so that any retrogressed ridge to the W or NW (should it evolve) is shunted back east by the jet stream increasing from upstream and as a consequence LP being re-set in the Atlantic. This scenario would suggest a pre-cursor to some further, sustained warmth into the meat and bones of official summer - even if the initial burst of momemtum flattens the ridging initially and allows a (likely brief) more unsettled westerly pattern for a time.

Some of our best summers have displayed this sequence of events in early season, so the retrogression scenario of the extended period, should it come about, should not be treated as "summer is over before its officially begun" . It could well prove to be the opposite. On that basis, the present and upcoming spell of weather may well be just a taste of what is to come. So best not fret, just yet anyway, about the new month (and new season) breaking the weather down - it might not be for too long if it does happen

Have a lovely week and Bank Holiday weekend

 

Edited May 21, 2018 by Tamara