Model Output Discussions 12z 03/05/2016

[Matthew.]

I know others have mentioned already but could this become more of a trend Let's hope Knocker has to bring out his red crayon

Edited July 7, 2016 by Matthew Wilson

[knocker]

I must admit I cannot find anything in the ecm run to get excited about. Sunday to Tuesday sees us under the influence of low pressure and quite wet with periods of rain and showers. Wednesday sees a very brief transient ridge before another low moves into Scotland by Thursday morning.bringing rain to the north and quite windy. followed by another transient ridge which in turn gives way to more fronts moving into the north by Saturday morning. So by Sunday 12z we have a depression north of Scotland with the UK in a NW airstream and the next transient ridge poised. Temps for the week around average.

In other words precisely what you would expect within this upper air pattern..

Edited July 7, 2016 by knocker

[Frosty.]

Knocker isn't impressed but sidney loved those Gefs 12z perturbations!

[knocker]

Actually he's more impressed with the GEFS anomaly which does show brief ridging for three days 15th-18th but the overall pattern is basically unchanged.

Edited July 7, 2016 by knocker

[Frosty.]

This is much better than the Ecm 12z ensemble mean last night, the Azores high ridges in much stronger with increasingly fine and warm weather across the southern half of the uk from late next week onwards.. I think this is encouraging in a summer so far starved of summery weather!

[knocker]

The ecm 6-10 also shows a brief incursion of the HP although no great shakes temp wise, tentatively backed by NOAA. Before both revert to general westerly flow in the later period and with LP to the NW and HP to the SW again the tendency for a N/S split but with an indication of height rises the SE that part of the country will fair a lot better. Temps around average perhaps sightly above in the south.

[William of Walworth]

I keep trying to understand the disacrepancies between knocker's anomaly charts, and charts posted by Frosty and others today, which do seem to show distinct increases in HP influence or even actual usefulness! for summer lovers -- in the South at least.

 

Are short term run-to-run charts utterly unimportant compared to longer-period NOAA caution? I know John H would say yes, and knocker too, but I still don't get how big the discrepancy is today.

Or is NOAA anomaly a 'lagging indicator' as they say in economics?

Edited July 7, 2016 by William of Walworth

[William of Walworth]

More pragmatically/personally, our weekend from next Thursday (near Trowbridge) would rule our world if most of Frosty's charts above end up being confirmed(ish).

 

Especially after the failed HP influx that was at one point starting to be predicted for the last weekend of June for the S ... but which never turned up!.....

 

More runs needed, FI unreliable,  etc etc but still!

Edited July 7, 2016 by William of Walworth

[johnholmes]

24 minutes ago, William of Walworth said:

I keep trying to understand the disacrepancies between knocker's anomaly charts, and charts posted by Frosty and others today, which do seem to show distinct increases in HP influence or even actual usefulness! for summer lovers -- in the South at least.

 

Are short term run-to-run charts utterly unimportant compared to longer-period NOAA caution? I know John H would say yes, and knocker too, but I still don't get how big the discrepancy is today.

Or is NOAA anomaly a 'lagging indicator' as they say in economics?

The anomaly charts at 500mb, the 3 you see me regularly quote are 'mean' charts at that height for the 6-10 day period and with NOAA only also for the 8-14 day period. So one has to be very careful how one uses them and then suggests what the overall weather might be. With care they are a very useful tool to give a good indication, in excess of 70% accuracy, for what the upper air pattern will be for much of the period being quoted. Obviously in some cases the actual weather will be somewhat different to them. A spell of 24-48 hours with more emphasis on either settled or unsettled is quite possible to get within a somewhat different overall pattern. Like I say they are very useful IF used carefully and with the success rate first shown several years ago but still showing much the same accuracy now.

Hope that helps William. Please use my pm if you want to ask any questions. I am always happy to talk weather.

Edited July 7, 2016 by johnholmes

[Frosty.]

11 minutes ago, William of Walworth said:

More pragmatically/personally, our weekend from next Thursday (near Trowbridge) would rule our world if most of Frosty's charts above end up being confirmed(ish).

 

 

Well I'm seeing some positive signs William, certainly the ecm and gefs mean have improved so hopefully some fine and warmer weather isn't too far away, at least for the south of the UK but we have an unsettled and cooler spell to get through first...fingers crossed for the rest of this summer. :- )

[William of Walworth]

Thanks John -- very informative-- and Frosty.

 

I may well take you up on that PM suggestion before too long John, but for now ... keep the synoptic updates coming, everybody. Very educative and interesting..

Edited July 7, 2016 by William of Walworth

[Frosty.]

4 minutes ago, William of Walworth said:

Thanks John -- very informative-- and Frosty.

 

 

No worries William :-)

[knocker]

A fairly cloudy and muggy day today for many in a moist SW airstream before rain arrives during the early hours of Saturday.

As for next week the GFS has us under the influence of low pressure centred to the north until Thursday So probably a showery regime with temps below average.Then a transient ridge/HP moves slowly east and is influential until Sunday, certainly in England, bringing some warmer temps (average or a little above) and drier conditions. This then gives way to a westerly regime for the rest of the run with periods of wind and rain but best ignored as in this mobile set up it will no doubt be all change in the next run.

Edited July 8, 2016 by knocker

[summer blizzard]

GFS and Euro want to bring a transient ridge over the UK from days 7-9 which may please some however to be honest, the rest of the 0z run is pretty awful. 

Indeed GEM does not even go for the ridge really..

 

[mb018538]

GFS and ECM are keen to bring in a brief interlude of high pressure by day 8....how long this lasts, or even if it builds in at all. I guess our best hope is that it does build, and the models are overcooking the low pressure influence after.

[knocker]

The ecm best described as very unsettled with the usual interplay between the HP and LP Temp varying around the average depending which phase we are in. Be afraid, be very afraid.

[Frosty.]

40 minutes ago, knocker said:

The ecm best described as very unsettled with the usual interplay between the HP and LP Temp varying around the average depending which phase we are in. Be afraid, be very afraid.

This is what sidney thinks of knockers chart above

 

[knocker]

No obvious sign from the EPS of any pattern change in the next 14 days.

[Tamara]

I posted this yesterday, but there was a problem with the links, and so I withdrew it as it was hard to follow without them, and also didn't make sense with them either ! because all the dates of the charts were wrong  I'm very much hoping when this arrives re-posted in its rightful place, that all will be fixed :-.

Faith in the Global Synoptic Dynamical Model continues to illustrate its specific value as a medium to longer rang tool.

The previous update dealt at length with the likely crossroads ahead for this summer. In a nutshell, the theme was 'in the balance'.

All the details and explanations available here.

In addition the previous Spring updates gave a lot of background information about how the expected changes from Nino to Nina might cause a few headaches as summer approached. The underlying fear was that timing might be completely wrong. The hope that was dwelled on rather more, was for an ocean/atmosphere disconnect that would mean a La Nina type summer would at least be delayed.

The former happened, the latter didn't. Therefore, GLAMM has fallen rather further than hoped a month back, and reality has met the most pessimistic end of expectations hinted at in the previous summary, but that had not been overly elaborated on to avoid appearing to write summer off before it had hardly begun!

So, unfortunately that balance has tipped towards the low angular momentum state and all that entails when correlated to expected summer patterns as described as the risk in those previous updates - and the UK/Scandinavian upper trough with supressed Atlantic jet stream scenario has won the day.

Easterly wind momentum from the sub tropics has propagated to the Pacific and overwhelmed the last vestiges of Nino atmospheric circulation/ocean coupling. Westerly wind inertia in the Pacific that was ebbing away (too) quickly through the Spring, has not lasted long enough to at least part influence our summer and produce its latent potential for Rossby wave induced West European ridging and more sustained fine seasonal warmth

NB:  With El Nino summer ridges in mind (more famously such as 2006, 2003 and 1976) the previous  Spring updates dealt in parts with why last years Strong Nino didn't provide effective summer ridges to sustainably benefit the UK beyond the early part of last July.  There was actually a lot of heat produced - unfortunately that occurred just to our east and south east. Rather a broad-brush assessment admittedly here, but nonetheless in that respect any strong ENSO event (Nino or Nina) is neither generally beneficial for either UK summer heat, or sustained seasonal winter cold.

The Global Wind Oscillation reflected the above changes to a low AAM state by diving into -GLAAM territory (for the first time for exactly a year) and completed a Phase 1,2,3 orbit as representative of a switch to a Nina based atmospheric signal.

On cue, the weather deteriorated away from the late Spring anticyclone that had given NW Britain at least some sparkling blue skies and sunshine and replaced it with the long wave troughing that has plagued us mostly since.

In the last week or so, on the back of some amplification of tropical convection passing through the tropics from the Indian Ocean, there has been some attempts to add a modest percentage of westerly winds back into the atmospheric circulation from the tropics - and, to balance the books, scrub out some of the surplus easterlies in the Pacific.

 There has accordingly been a (temporary) rise in GLAAM  as we start July.  (Note the extent of the Nino circulation signal collapse in late May as total atmospheric angular momentum started diving into June)

No coincidence that the downstream response to the attempted recovery in GLAMM has seen a weak push of the Azores High to try and edge its influence north east towards southern Britain and into the mainland part of the nearby continent in the current period. However, despite some slight recovery in temperatures (mostly restricted to the south)  summer proper has only returned across the channel.

Were this rise in GLAMM to be sustained, it would indicate that summer hopes might finally take a turn for the better here in the UK as well.   This latest sequence of current weather is a reflection of the GWO ( chart above) pushing into the Phase 4 part of the depicted orbit ( a Nino pre-cursor phase).

However, with the atmosphere now starting to add net easterlies back into the circulation, propagating from the tropics, atmospheric angular momentum is set to slide once more.

On that basis we are highly likely to see a further GWO Phase 1,2,3 orbit being lined up to echo the early/mid June trend. Rinse/repeat of last month beckons with next week cool and very showery just as the similar period in June was, as the upper trough gels across from the North Atlantic between Iceland and Scotland into Scandinavia.

These charts fully advertise GWO Phases 1 and 2 low angular momentum state for high summer. Its easy to see how secondary lows can develop on the SW perimeters of the upper trough and delay the ridge in the Atlantic so that programmed rises in pressure are flattened out and downgraded southwards

Phase 3 GWO depicts retreat of the trough into Scandinavia and the Azores High yet again beginning its attempt to ridge NE. This kind of evolution reflects much of what we saw already since June, and with the atmosphere stuck in this cycle, is reasonable to expect to keep seeing.

 

I think that current NWP indications of the next 'attempted' improvement to occur towards day 10 are reasonable enough on current extratropical (GWO and AAM) expectations.   Latest GEFS forecasts echo that expectation of another low angular momentum orbit, with a question mark over how long it dwells around Phase 2/3.  That will decide how quickly the trough clears away into Scandinavia and pressure is able to rise from the SW ...before the next trough crosses the Atlantic.

(P.S That GEFS broken clock disclaimer of finally arriving in -ve GLAAM territory did verify as hinted it would sooner or later in the previous post)

However, with that said, the GEFS low AAM exaggeration bias is sadly less relevant now we are back in a true Nina like atmospheric circulation regime. You could think of it a bit like how the models handle the Atlantic so well during disturbed cyclonic phases as opposed to being prone to over progressive modelling in trying to remove anticyclones during blocked patterns.

With tropical convection beating a retreat twice already before arriving in the Western Pacific since the change in signal at the start of the summer, and with the seasonal longwave pattern entrenched in this feedback rut, there is no quick end in sight to this mostly dominating low AAM state.

With all the above analysis in mind, best not to have too high expectations of any future modelled northward extent of the Azores High. This might well continue to be watered down as the models come into the higher and higher resolution timeframe  The next few weeks looks very much to echo the last few weeks. Its no surprise that the extended ensembles and anomaly H500 charts refuse to blink and summer is slipping by unremarkably as a consequence

There is always the chance that any warmer advection sequence whenever the Azores ridge tries to head north-eastwards might provide some humid conditions. But overall there is no real sign at the moment of anything properly and sustainably above average (at best)

August is yet another summer month,  and it also involves changes to the long-wave pattern which might assist some improvements (based on the assumption the summer rut pattern persists). But that is too far off and will take care of itself as time comes rather closer.

[DR(S)NO]

On 2 July 2016 at 10:48, knocker said:

 

 

 

Thank you Tamara for that wonderfully concise update on the current woeful conditions ... It certainly feels like this Summer is going to be particularly unremarkable in terms of any decent spells. Feels very much like a rinse and repeat type of Summer and the wonderful weather ( up here) of June seems a lifetime away now!

I wonder if the current patterns will have any influence when it comes to the Autumn and then Winter weather.

Edited July 8, 2016 by DR(S)NO
Can't attach correct post

[Frosty.]

The Gfs 6z op run shows an increasingly cool unsettled spell in the short term but then high pressure builds in from the southwest  through the second half of next week with increasingly fine and warm weather, especially further south. There is another changeable blip in low res which is followed by more high pressure and warmth.. considering the way this summer has turned out so far, this run should be welcomed!

[phil nw.]

1 hour ago, Frosty. said:

Meanwhile the Eastern US is having a wonderful heatwave while our summer goes from horrible to worse.. they get all the heat in summer and all the snow in winter while we get never ending Atlantic muck!

Indeed Frosty and look at Arctic Siberia's expected afternoon temperatures over the next few days as per the GFS.

hard to take when they are so much further north!

See the cool plunge of air modeled over our side of the Atlantic via that upper trough.

Now we know where our Summer heat has gone.

 

 

[Frosty.]

10 minutes ago, phil nw. said:

Indeed Frosty and look at Arctic Siberia's expected afternoon temperatures over the next few days as per the GFS.

hard to take when they are so much further north!

See the cool plunge of air modeled over our side of the Atlantic via that upper trough.

Now we know where our Summer heat has gone.

 

 

I'm just gobsmacked by the bad luck we are still having. .no winter, no spring and so far. No summer. Surely it can't go on like this month after month!

[Frosty.]

Time for some good news, despite the awful summer we are experiencing, the GEFS 6z mean shows high pressure ridging in later next week which lasts into week 2 with a spell of settled and warm weather, at least across the south of the UK. Further on the Azores highs influence does wax and wane but shows occasional spells of settled and warm weather, again, more so further south.

[Frosty.]

Looking closer at the GEFS 6z perturbations, almost all of them show high pressure either building in or already centred over the UK by T+168 hours so a spell of generally settled and warm weather could be  just a week away, in the meantime the next few days look warm across the s /e. :- )