Model Output Discussions 12z 03/05/2016

[Man With Beard]

38 minutes ago, Summer Sun said:

ECM is joining the party for next week sending up some very warm to hot air

And another model goes for the jugular... trying to think of reasons why this might be wrong ... likely that ECM has overdone heights to the north, preventing the northwards movement of the Atlantic low - if it has that wrong then CS's idea of south-easterly corrections could be right.

The last week has been a reminder of how hard it is to get a plume to the UK. South to north flows are easy to interrupt (and vice versa). 

But the direction of travel today has been towards the plume reaching at least the SE. 

Many more runs needed!

Edited August 17, 2016 by Man With Beard

[knocker]

A quick look at the NOAA 6-10. Also showing some nice amplification so could be interesting. I'll need to pop down to see Sidney in the morning.

Edited August 17, 2016 by knocker

[Nouska]

38 minutes ago, knocker said:

A quick look at the NOAA 6-10. Also showing some nice amplification so could be interesting. I'll need to pop down to see Sidney in the morning.

That's one whopper of a positive AO for August ......

 

.... must look back the 'compare year' feature in the Meteociel archives - they now go back to 1871!

http://www.meteociel.fr/modeles/archives/archives.php?day=17&month=8&hour=12&map=4&mode=1&type=ncep&region=

[Man With Beard]

58 minutes ago, knocker said:

A quick look at the NOAA 6-10. Also showing some nice amplification so could be interesting. I'll need to pop down to see Sidney in the morning.

On the brink of being mega for heat ... and on the brink of not being, too.

ECM ensemble 500mb charts looking similar to the op - that's significant imo. 

 

[knocker]

The EPS anomaly is not dissimilar and the upper air pattern is conducive to some transient heat but it's very much a knife edge scenario as any slight adjustment to the upper air would have the significant WAA move east

[William of Walworth]

Just idly wondering  what would make any heat of that kind become less transient? Could that kife-edge situation head in either direction? I guess the form-horse for now would be for any influx of any serious heat over the UK to weaken and cover less territory.

Personally I prefer less hot and with a more stable/settled/longer-lived HP controlled/influenced outlook, but I think prospects for this immediate weekend followed (perhaps) by drier weather returning after the weekend, are influencing my view a tad on that!

Edited August 17, 2016 by William of Walworth

[Man With Beard]

Any fans of heat need to tune into the GFS 18Z op run right now. It's out to T162 so far and it's taking the definition of global warming to a whole new level. Don't believe it just yet though...

[TomDav]

Looks like a very deep low over the pole for the time of year

Edited August 17, 2016 by TomDav

[knocker]

Today

Last day of the fine spell for all as the depression moves in. Cloudy in west and quite muggy. Thick fog here at the moment.

Talking of knife edges the GFS this morning

The depression, and associated fronts, duly arrive on the scene tomorrow and is centred over northern Scotland by 18z on Saturday. Thus a wet and windy couple of days with the strongest winds in the south. The low continues to drift east and fronts associated with a new  depression tracking NE to be south of Iceland (not a million miles away from the old ocean weather station India)  quickly arrive on the scene bringing more wet weather for Sunday.

Now this where we have the variation from previous runs. This low now tracks east to be west of the Hebrides 988mb by 00z Tuesday. I think it worth noting here the position of the upper in relation to previous forecasts. It's now positively inclined and this makes a huge difference to the surface evolution.

The low continues to track east and slowly fill allowing the Azores ridge to extend into the UK from the south west and not an unpleasant few days for most. Of course there is nothing to say this interpretation is on the money but you wouldn't bet the house on it not being in the right ball park. The ecm may be of some interest this morning.

.

Aquick look t the GEFS anomaly and it has similar alignment of the upper trough.

Edited August 18, 2016 by knocker

[Paceyboy]

After yesterday's runs, GFS is like the morning after a great evening and night out. A hangover and the idea it was a good night but not much more to go forward! 

UKMO not bad!

ECM prone to fail with that precarious flash of heat. 

[knocker]

Well good luck with picking the bones out of this morning's runs.

The ecm evolution next week is complete different to the GFS. Until they sort out the upper air pattern into some sort of agreement then divergence will continue. As it happens the ecm is fairly consistent to last night for a while and slowly drifts the main Atlantic low south creating a slack area of pressure over the UK and some not too bad temps in the SE quadrant and it ridges HP NE before tracking frontal systems in again from the SW by the end of the run. I think all of this best left in the pending file for 24 hours.

 

[Summer Sun]

ECM gives further opportunities for very warm or hot temperatures during next week

UKMO doesn't look too bad into next week once this weekend's unsettled blip is out the way

Edited August 18, 2016 by Summer Sun

[carinthian]

Another rather cool and cloudy day dawns in Central Europe. Fairly high confidence of a strengthening of the Euro ridge over the coming days and should miss worse of the UK weekend depression. Could be a nice week for much of Western/ and Central Europe next week with some late summer sunshine and warmth.  Long overdue in these parts.

 C

[Man With Beard]

Only 2 out of 22 ensembles do not reach 19C at 850hpa over the UK by D8. That is truly staggering.

It's a big change from the 00Z run where such hot runs were slightly in the minority. Also, the ECM ens strongly suggest the really hot air will stay just over the channel.

With this sinking trough to our west scenario, I expect the ECM op to lead the way between T96 and T144. Recent runs suggest the trough will be far enough to the west for most of the UK to be dry and sunny for most of next week, and a toss up over whether that means low 80s or mid 90s for the SE. 

In the more unreliable T168-T192, the ECM op seems keen to bring hot air back in from the SE. I think we're 48 hours away from the evolution for later in the week yet. 

Edited August 18, 2016 by Man With Beard

[Summer Sun]

We certainly can't rule out a hot spell next week as the postage stamps from the 06z show - a week today is shown below

[knocker]

I've just come in and rather foolishly I glanced at the outputs. No big surprise with the GFS as it's now realigned the upper trough back to neutral.and we are back to some WAA and very warm temps next week..

Given that the general trend, also with regard to the EPS, seems to be to orientate the trough in a favourable position with some decent amplification vis the ridge to the east, conditions are becoming quite favourable for two or three days of quite warm weather in the south next week.

[Scorcher]

One thing's for sure, it certainly won't be cool next week with that trough setting up camp to our west. How warm is still open to question, but it's looking very promising, particularly the further south and east you are. It's looking like it could turn out to be a very warm second half of August- something we haven't seen for a long time.

[Tamara]

On ‎16‎/‎08‎/‎2016 at 15:30, Tamara said:

So, to translate all that synoptically, whilst we are returned to a feed of depressions from the Atlantic, it will take little amplification within the sequence of these lows to push some hot humid air northwards, courtesy of sub tropic flow, and provide further brief heat spikes.  These can't ever be guaranteed, but such amplification is quite conceivable because with the pattern not yet fully retrogressed there is band width for the Azores High to ridge eastward and sufficiently far northwards for at least some transitory very warm air advection to occur downstream ahead of any deepening and slowing Atlantic lows..

On that basis, whilst the extent of the intense plume as shown on the ECM 12z last night is questionable, the re-appearance of a similar overall type of synoptic on the GFS 06z to whatever lesser degree, is not just coincidence.  Whilst it doesn't represent another country wide settled spell (the outlook is certainly back to a changeable one and suggests something of a NW/SE split instead beyond the unsettled conditions of the weekend and start of next week)  there remains plenty of opportunity for interest in glimpses of summer before the new autumn season officially begins. Also, until the pattern further retrogresses (watch the tropical signal for that), it will be very hard to achieve temperatures below the seasonal average - even if it feels cool in the more unsettled and blustery interludes such as it may well do this weekend.

With the re-emergence of the amplified mid Atlantic ridge in mind, any modelled synoptic that plays around with the ridge toppling over a cut off low entrapped with hot humid air is quite conceivable also - before any polar maritime influence eventually arrives from the west.

Reasons to be (cautiously) very cheerful that the upcoming rude intervention to the fine warm weather might well amount to just an annoying, albeit definitely inclement blip.

Please excuse me quoting myself, but what was conceivable a couple of days back is now not only becoming increasingly likely, but is upgrading in consensus of some potentially not inconsiderable late season heat. Its the NW'ward extent of this heat though, that at present holds the greatest uncertainty.

The outlined upper broad-scale pattern is still evolving consistently along the expected lines outlined in the previous post, but confidence is starting to grow that the amplification potential within it, is not just greater than could be anticipated, but also that the upstream amplified wavelengths are aligning very nicely for tropical continental heat to advect northwards in an ideally aligned dome to cover, at the very least, southern and central UK. Knocker has already described the surface detail processes and possibilities very well. 

 The GFS 06z operational has corrected its progressive predecessor and, at face value at least, suggests a sizzling late summer week which lasts just about into the Bank Holiday weekend. This is obviously just another operational solution, and too far off to have ultimate confidence in and also obviously too far off to trust the widespread nature of the heat indicated by it

 At this stage its the growing consensus of the overall pattern around days 4/ 5 in all the models, specifically the phasing of the low in the NE Atlantic, which will determine the potential plume and its extent, that is far more important than the daily surface details which will always change from one output to another. That consensus at the moment encouragingly continues to back westwards the trend of amplified warm/hot air advection arriving from the nearby continent.

The updated GEFS ensembles reflect a move away from the flatter progressive overnight set and the mean at day 5 reflects this well with the pattern, as reflected by the higher uppers, backed further west. This improvement continues to day 6 and becomes more marked in its contrast to the much flatter preceding set of solutions.

 

The ECM London ensembles have jumped overnight for the day 4/5 to day 10 period. At this range, for that period, arguably one of the best set of ensembles for the summer as a whole. The importance here is that although the operational remains one of the hottest solutions, as it was to a greater still extent yesterday evening, it has clearly been leading the pack.

 

The cooling off trend suggested beyond the day 10 period reflects the discussion in recent posts with regard to the evolving progression of the amplified Atlantic ridge - and how evolution of the upstream pattern ties in with direction of travel of atmospheric angular momentum.   The continued amplitude of convection in the Western Pacific over the medium term looks wholly supportive of propping up the atmospheric circulation with sufficient westerly wind propagation to prevent slipping back into -ve GLAAM territory . So supplying the downstream movement of Rossby Waves that sustain the indicated very warm meridional pattern in the Atlantic and European sector through next week, and which follows the interruption spoiler courtesy of a weekend hooligan.

Its a continued watch as to how much amplification can be squeezed out of this, and for how long. The likelihood remains that following the Bank Holiday period, the tropical forcing signal will relax, as the current activity in the Western Pacific ends and starts another cycle in the Indian Ocean. This will have the effect of a renewed slide in angular momentum and, eventually the movement of the Global Wind Oscillation more decisively into Phase 1.  Until this time, tropical forcing will offset parity of the GWO at a neutral signal on the pattern, and the status quo prevails.

 

The synoptic response to further falling angular momentum as reflected by Phase 1 GWO would be the de-amplifying of heights over NW Europe and mean that the amplified ridge in the western Atlantic becomes the main player further east and invites (relatively) much cooler air from the west or north west and quite possibly less settled in general too.

However, as mentioned in the last post, much can interfere with these processes whichever way, not least hurricane development and trajectory beginning well away in the tropical southern Atlantic that can never be modelled reliably at any range.

So, despite a decidedly poor weekend, it seems that summer proper for many may well be far from written off in its official final days. There is the cautiously growing prospect of more fine days and blue skies to repeat next week, and with it this time, temperatures potentially breaching the 30C barrier - all helping to quickly dispel any sense at all that an unpleasant weekend is a portend to early arrival of autumn.

Fortunes of those furthest NW are admittedly most uncertain close to the trough in the NE Atlantic. However, the apparently growing trend  to 'warm this out' and take it south does hold hopes for further improvement adjustment and helping to take the very warm uppers furthest north.  This trend needs to gain some further consistency however in the next few outputs if the heat spike is to maximise its longevity.

[johnholmes]

from Tamara

The synoptic response to further falling angular momentum as reflected by Phase 1 GWO would be the de-amplifying of heights over NW Europe and mean that the amplified ridge in the western Atlantic becomes the main player further east and invites (relatively) much cooler air from the west or north west and quite possibly less settled in general too.

However, as mentioned in the last post, much can interfere with these processes whichever way, not least hurricane development and trajectory beginning well away in the tropical southern Atlantic that can never be modelled reliably at any range.

I think the above 2 paragraphs are pretty important as to whether much of the UK gets a late summer heat spell or a cooler flow from N of West. To me I would back the latter option at the moment, I stress at the moent. The anomaly charts I use, taking us out almost to the end of August are below.

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

They do not show a huge amount of similarity in how the major troughs/ridges are aligned.

NOAA below, and it has, over the last 2 days, very slightly increased the +ve signal in the western Atlantic as well as showing just a slight indication of ridging in the same area.

Of course all it needs is one of these, link below to get into the North Atlantic proper and all best (sorry forecasts will be off).

Interesting trying to decide just how the BH weather will turn out for most of us.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

 

And just for another slant the latest Met O 6-15 day outlook. To me they appear to be trending by BH weekend to a NW-SE split with the changeable weather extending SE in that period? I may have misinterpreted it though?

http://www.metoffice.gov.uk/public/weather/forecast

apologies to the team for putting an actual forecast in but I hope I have entered enough model comment to let folk see the Met O output in model context?

[knocker]

 

[Captain Shortwave]

So a day further towards the potential hot spell next week and good agreement on cutting off the Atlantic low for at least a time next week allowing it to sink south and pull some very hot air towards the UK.

Day 5 (GFS/UKMO/GEM)

      

All show a fairly slack southerly flow over the UK, all three would deliver mid to high twenties in the south, a little cooler in the north as the warmer air hasn't arrived just yet. The GEM makes a lot more of that ridge extension out of western Russia, this has an effect down the line.

 

Day 6 

      

Again all three look good, the GFS/UKMO show a southerly feed still over the UK with temperatures pushing into the low thirties with mid-twenties for the rest of the UK. The GEM with that extra ridge from the east begins to set up an easterly that would make mouths water during the winter, here it would deliver a fairly dry and very warm set up as opposed to the GFS/UKMO which go hot or potentially very hot beyond the middle of next week.

One thing is for sure, there is increasing consistency on some of the key variables required to deliver a potent pulse of hot continental air to the UK, the details will change but the trend is certainly there. Maybe, just maybe this summer will go out on a high and for many on here a very big bang.

[Matthew.]

Could nearly the last week of August be the warmest of the whole summer? The stalling of the Low resembles something like July 2006 had. Certainly a chance of the warmest summer scenario coming to fruition

Edited August 18, 2016 by Matthew Wilson

[Man With Beard]

Right, it's that time again - it's ridiculous GEFS outlier of the evening. 

This is the coolest overall chart I could find. The 16C 850hpa line barely touches the SW. Temperatures may not even reach 28C ...

 

now for the mean chart... :-0 :-0 :-0

    

Getting towards 50/50 odds that the 20C 850hpa line will cross the UK now.

[Fourty Point Three Degrees]

12z was a blowtorch of a run, high 850s all the way, if this comes off it will be one of the best Augusts in yonks.

[knocker]

Not a bad example of increased amplification, a temporary cessation of zonal mobility and a meridional jet and WAA over the UK