Model output discussion - summer rolls on

[Mike Poole]

2 minutes ago, Reverse Zonality said:

Based on one ECM run in deep FI then yes. No real sign of the Atlantic waking up as such. Low pressure threatening western and some central parts but much to be determined in terms of track and strength of both the low and the blocking high. I feel we won't know the extent of any thunderstorm or heat coverage until early next week at the earliest - still a lot of differences with each run across the models.

Difficult to call beyond 5-6 days let alone the whole of August. I'll put my faith and attention into the longer-term MetO outlook. Once they suggest a return to Atlantic dominance I might take notice.

Yes I agree, looking at the CFS for August, no sign at all of an Atlantic resurgence, no point looking at just one run, so here's the last 5 z500 anomalies for August:

[MKN]

2 hours ago, Frosty. said:

Shame about the Ecm 12z op..however, it's probably being too progressive, nothing like the scorching 00z, especially by the end..we shall see, I still think the best of this amazing summer is still ahead of us.☺

The 12z appeared to me to be poor looking at the 850s only but looking at the relatively high pressure still close to the south then here at least would probably still see largely dry day/s and temps 21-24c. Given its the poor run out the bunch it's not to bad.

[blizzard81]

13 minutes ago, Mike Poole said:

Yes I agree, looking at the CFS for August, no sign at all of an Atlantic resurgence, no point looking at just one run, so here's the last 5 z500 anomalies for August:

You can't deny the trend though. My best estimate is certainly more changeable/unsettled as we head towards August but at least it won't be cool. 

[Rocheydub]

Especially us, more west of the S/E England gang here!

[Guest]

18z a little further east with the low. Consequently the hottest conditions merely glance the SE on Friday. More east/west corrections to come  #enjoytheride

edit: big differences compared to the 12z by t+156. Less thundery at the weekend. It'll be interesting to see how this secondary low interacts with the blocking high after next weekend - will the GFS push it through?

Edited July 21, 2018 by Reverse Zonality

[Mike Poole]

9 minutes ago, blizzard81 said:

You can't deny the trend though. My best estimate is certainly more changeable/unsettled as we head towards August but at least it won't be cool. 

Yes, we are certainly in a transitional period, from home grown heat with an anticyclone over or close to the UK for the last few weeks, but not to Atlantic rubbish, more to a Scandi high situation, with possible plumes from the south interspersed with lows from the Atlantic that never really make it - that's my assessment anyway.

 

[Frosty.]

9 minutes ago, Reverse Zonality said:

 the hottest conditions merely glance the SE on Friday. 

The 18z is hot all next week further south by southeast with temps in the high 20's / low 30's celsius, nearer 30 / 32c for London and the SE..amazing sustained heat for the SE next week.

Edited July 21, 2018 by Frosty.

[Mike Poole]

8 minutes ago, Frosty. said:

The 18z is hot all next week further south by southeast with temps in the high 20's / low 30's celsius, nearer 30 / 32c for London and the SE..amazing sustained heat for the SE next week.

Yes, Karl, good 18z - so far, I've holded off posting about it because of  the low to the west of the UK what is it going to do, act as a heat pump or rain on our parade?  Here at T222:

I still think this pattern will back west before we get to T0 so all good tonight!

[summer blizzard]

Looks to me like we are in limbo but with a lean towards abnormally weak Atlantic due to +GLAAM due to the Pacific pattern. 

You see here that strong westerlies in the Pacific during April and then followed by an even stronger event during May (this event went through the entire Pacific) created a strongly displaced mid-lattitude high signal.

This tropical forcing however has now abated with a fairly benign picture forecast..

Although the background pattern is one of positive GLAAM as Tamara has pointed out (hence why her thoughts are for the trough to remain west and produce a ridge to the east) that is ultimately just a holding in my opinion (though it may hold a good two weeks given that the trade burst only really put the Atlantic in control for a week). If we see a new westerly wind burst push through the Pacific as per April and May/June then it's likely the ridge over Scandinavia will retrogress and we may well see an August to challenge 47 or 95, if however we see another trade burst without much fight to it's west then the holding pattern is probably weak enough that the Atlantic wins and we start running down the clock on summer 18. 

..

Tonight's GFS18z is messy and humid. The low just sits off Scotland doing enough to keep the plume east but not enough to push the warm air away. A recipe for showers and humidity.

Euro at least was quite a bit cleaner..

[Mike Poole]

Pub run going on a monster plume adventure, here at T336

I think this is the third time in 5 runs the GFS has done this, week after next could be very interesting!

[Djdazzle]

GFS on one this morning doing its usual overblowing of the low even at T72. Totally underestimating the block strength. I think the westward correction will come this evening.

ECM is an improvement on last night.

There are quite big differences in the models st T48 in terms of the low pressure modelling.

So still massive uncertainty even for late this week.

Edited July 22, 2018 by Djdazzle

[Guest]

Those spikes of high 850s later next week are largely gone on the GEFS. Anyone looking for the really hot stuff might have to wait until early August - a significant cluster still brings a plume event to our shores.

[MR EXTREMES]

33 minutes ago, Reverse Zonality said:

Those spikes of high 850s later next week are largely gone on the GEFS. Anyone looking for the really hot stuff might have to wait until early August - a significant cluster still brings a plume event to our shores.

I stick with ecm as gfs has been a nightmare recently.

The pattern is not going anywhere fast.

North south split but ecm pushes the warmth and dryer weather back in rinse repeat.

Nothing is going to far East this wall in Scandinavia and down into southeast Europe in fact other than few little lows floating around in the Atlantic.

and there just no momentum.

I'd also like to say that were really into drought territory here in the south, not seen a single drop of rain for sometime.

Nothing substantial anytime soon either maybe some instability towards the end of the week.

Certainly a year to remember so far.

With flat lined solar activity I don't see a major change anytime soon.

[mushymanrob]

to illustrate the accuracy of the noaa 500 mb charts...

heres the chart for 8-14 days ahead published on the 15th july. in comparison to the gfs predicted chart for the 26th (mid point at the 8-14 days chart starting on the 15th). after much 'too-ing and fro-ing' the ops are now agreeing with the noaa's. not on just one run, but on all current ones that are unlikely to change much before the 26th. the main feature to note is the predicted position of the mean upper trough in the north atlantic, and outgoing flow over the north coast of norway/scandinavia.

pretty much bang on.

 

[The PIT]

Looking at both the GFS, UKMO and ECM show the clue to be the actual position of the low pressure in the Atlantic. Differences between the three are showing at T96 and the exact placing of this system will decide if we bake or just mildly done. The overall look is slightly cooler after this week away from the south and south east and more pleasant conditions.

[Mike Poole]

Model output good again this morning, although GFS a bit iffy.  I wonder if the real plume opportunity is a little later though, T336, here the GFS parallel and a couple of the GEFS perturbations:

5th August has come up as interesting on previous output, so my bet for the peak temperature.

Edited July 22, 2018 by Mike Poole

[Weather-history]

NOAA 96hr chart from yesterday

[Summer Sun]

This morning's ECM has widespread rain for ROI, NI and Scotland at D4 (Thursday)

The others have some rain but nowhere near as widespread in the locations mentioned above

[Captain Shortwave]

This coming week looks for some to be the hottest of the year, though northern and western areas will be more mixed with some rain at times.

GFS I know, but a rough guidance for the level of heat we will see and where the hotspots will be. I will use the arpege here as well for the earlier days of the week.

Monday

    

Given we can add a couple of degrees to this I still think 30C is acheivable across a good part of central and eastern England (Even as far north as Leeds perhaps). Very warm elsewhere away from the fronts across the north west (Aberdeenshire could do well from the fohn effect though). 32C looks to be the high across the interior parts of East Anglia which makes sense given a WSW wind, if there is enough strength to the wind then even the coasts of Norfolk and Suffolk could get close to 30C.

Tuesday

   

The cold front looks to have moved south east to affect Cumbria and Northumberland, again Yorkshire southwards looks hot though perhaps a degree or so down on Monday though 31C looks possible in similar locations to Monday's high. Rainfall by this point looks to have died out by this point so just more cloud than anything else.

Wednesday

   

Pretty similar conditions with the sunniest weather across Central/Southern/Eastern England with the highest temperatures, cooler elsewhere with more cloud and a few showers. The high looks to be around 31C again.

Thursday

More of the same though divergences do occur between the GFS and others with the GFS more keen to keep hotter air over France away from the UK, As such the GFS wants similar temperatures to Tuesday and Wednesday (31C), though the UKMO and ECM would probably deliver closer to 33C and have the heat spread further north and west.

Friday

Even the progressive GFS gives a high of 30C which could correspond to around 90F (32C) in reality, again the Euros are further west with the heat with the 16C isotherm grazing the SE corner so possibly getting close to 35C if we can hold a straight southerly feed to pull in the higher 850s from France. 

So this coming week, average to warm across Scotland (Eastern areas the exception where it could be very warm at times). Northern Ireland will have a similar fate with areas close to the Irish sea potentially seeing better conditions at times. As for England and Wales it will be very warm to hot at times but areas further north and west will be more at risk of a little rain and cooler conditions though exact detail is uncertain given the boundary will be over the UK throughout this week. The south east looks like seeing its hottest week in quite a few years though.

[Guest]

Seems like a fair bit of uncertainty after Wednesday unless you live in east anglia. Even if the heat is punted east quickly after a cooler spell (average at worse for many) heights could we rebuild.

[johnholmes]

Sunday 22 july

Not been around for about 2 weeks but have managed to keep an eye on the anomaly charts. Obviously I agree with the post from mushy above, one of my converts. They are wrong at times but not often but do have to be used with care.

Anyway,

 Ec-gfs both show similar to each other and also to the fri output, and from memory this has shown on a day or so previously?

Noaa also similar to ec-gfs and like wise to the fri chart

The upshot really is that the overall upper air pattern for 6-10 days is not going to be much different from what these 3 charts show. Minor differences in the positions of ridging and troughing will be all important as to how the surface pattern  shows on any one day. Much as is being commented on for the T+96 hour period.

The noaa 8-14 is, given its time scale, is less solid about the idea of heat from the south but the centre of gravity of the upper trough may still be far enough west to allow many areas, perhaps the infamous NW-SE split idea being in place into August?

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

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

 

As always the detail for the surface will come from the 2x or 4x synoptic outputs, and the T+96 charts may well show sonme corrections over the next 24-48 hours as these models get to grips with the actual position of the trough-ridge system.

Edited July 22, 2018 by johnholmes
spelling of course and text

[johnholmes]

Further to above.

Just looking at the Met O Fax charts and their surface positions suggest that the upper trough will remain west of the UK as weakening frontal systems push east.

If you look at their upper air charts (below the 120h Fax, you can see they also do keep the marked upper trough west of the UK. Perhaps by then a deep enough feature for it, not the ridge to the east, to be the dominant feature for the UK weather. Possibly just the far SE being in the 'hot' weather?

Interesting to see what does happen.

[Singularity]

Overall we’ve seen for Fri-Sat a move toward S and SE UK seeing a less hot but also much drier outcome, as the Scandinavian High looks just influential enough to stall the Atlantic fronts across northwestern parts but not enough to bring a continental flow except perhaps briefly for the SE.

My focus is therefore shifted to the next trough in the Atlantic chain. This has varied a lot in size and intensity between model runs, but overall there’s been a westward adjustment. However, the models have been hesitant to extend the Scandinavian high westward as well - the big heat plume seems to cause convective feedbacks that lead to a lot of very shallow lows that interfere with the ridge development.

Now and then, though, we’ve seen a run establish the westward expansion, usually via the inflation of a separate ridge ahead of that second Atlantic trough which then merges with the Scandinavian high. The 18z GFS of yesterday was the best deterministic model example of the past 48 hours, and the 00z ECM of today is not far off.

From that westward shift comes the potential for troublesome levels of heat - but this is now far enough away (1st week Aug), meaning enough time for complications within the hot air that may reduce its intensity, that my concern level is, for now at least, slightly lower than it was.

...though undeniably, the heat is quite capable of intensifying in situ before we reach late-August, so the reduced certainty of a severe event is offset somewhat by the increased upper potential limit i.e. just how extreme events could feasibly be.

 

If we avoid the very hot weather, a run of dry, sunny and warm or very warm easterlies is highly feasible, though continental lows may interrupt that from time to time - but that’s arguably the best of both worlds; a lot of fine weather but also some useful rain.

[mushymanrob]

14 minutes ago, johnholmes said:

Further to above.

Just looking at the Met O Fax charts and their surface positions suggest that the upper trough will remain west of the UK as weakening frontal systems push east.

If you look at their upper air charts (below the 120h Fax, you can see they also do keep the marked upper trough west of the UK. Perhaps by then a deep enough feature for it, not the ridge to the east, to be the dominant feature for the UK weather. Possibly just the far SE being in the 'hot' weather?

Interesting to see what does happen.

oh i hope not! i know im clutching at straws here, but flicking between the 6-10, 8-14 day charts would appear to suggest a weakening of the mean upper trough in the north atlantic, plus it shifts further south towards the azores. at the same time a strengthening scandinavian high?

naturally, as someone looking for a long hot spell (as opposed to the current mixed bag, as im sat under grey skies when it was supposed to be sunny) id hope future runs to have that mean upper trough as a weak feature over the azores/west of iberia, with a westward shift in the scandinavian high to produce a long southerly/southeasterly flow across the uk. thats what im hoping to see, but its not what id expect - which is little change from the current pattern.

[mushymanrob]

feasible !