Model Output Discussion - 1st July Onwards 18z--->

[Tamara]

https://forum.netweather.tv/topic/83477-model-output-discussion-1st-july-onwards-18z/page-29#entry3237007

 

A few days on, same "press F5" message essentially. Its still a matter in my opinion of when, and not if, the stalemate is broken

 

The closing period of July is fairly straightforward in broad brush terms with a disappointingly cool and at times unsettled several days ahead.   Atmospheric Angular Momentum remains (relatively) suppressed for this period with weak tropical (Madden Julien Oscillation) and extra tropical (Global Wind Oscillation) signals not forcing upstream changes on our pattern.

 

However, just because the signals are currently muted it doesn't indicate seasonality itself as an issue to lack of forcing on the pattern. Quite the contrary with the starkly compelling El Nino imprint forced on the atmosphere through July, which will cap the downside in angular momentum tendency, and it remains simply a matter of time before the tropical signal re-cycles and the blue touch paper is lit with tendency heading upwards once again

 

The negative GEFS bias to these forcing signals (pre-disposed to underplay AAM tendency in response to tropical forcing movement) as discussed by Stewart the other day should continue to be the cautionary word in extended GEFS GWO forecasts

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png.

 

It makes sense at most times anyway, but best to not read too much into longer range intra day output - and especially GEFS at the moment

 

Still the promise of better fortunes increasingly as we head through the early part of the new month with warmer and more settled conditions, gradually, extending from the south west

 

The latest ECM Dutch 15 day ensembles are consistent with a gentle warming trend through the start of August. In terms of the overall pattern progression into the extended period, a guide further east towards estimations of trough progression departing NW Europe with attendant cool air, is a good guide for us positioned closer to the direction of anticipated improvement

 

http://www.weerplaza.nl/gdata/eps/eps_pluim_tt_06260.png

Edited July 23, 2015 by Tamara

[Man With Beard]

Another interesting new feature on Meteociel - ECM ensembles spread. This morning, they show a tendency towards a warm-up and a decent pressure rise towards the end of the period - but a distinct lack of certainty too:

 

http://www.meteociel.fr/cartes_obs/ecmwfens_display.php?x=297&y=315

 

http://www.meteociel.fr/cartes_obs/ecmwfens_display.php?x=306&y=141&run=&ville=Londres&type=1&runpara=0

[Frosty.]

After an unsettled start to next week, the Ecm 00z shows high pressure building in from the south west with increasingly pleasant conditions, by the end of the run it looks like warmer continental air is poised to make inroads beyond T+240 hours.

Sorry about the charts being back to front

ecm500.168.pngecm500.192.pngecm500.216.pngecm500.240.pngecmt850.240.png

Cheers for that DRL

[Frosty.]

The Gfs 6z has a very summery low res with high pressure gaining the upper hand with most of the cool unsettled weather steered away from the UK to the northwest. The south and east in particular are very warm at times. So, although we are in for a more unsettled spell, there is light at the end of the tunnel, the 6z in FI would be very nice indeed.

Edited July 23, 2015 by Frosty.

[BlueHedgehog074]

Cheers for that DRL

Anytime Frosty.

While I'm at it, will do a quickish summary of the next 2 days using charts from the latest GFS run:

Friday - tomorrow will see a small surface Low Pressure system to the South of the UK (as shown on the 06Z GFS 500hPa and Sea Level Pressure chart below) track North-Eastwards bringing a spell of heavy rain over Southern UK from the West. Some of this could be quite torrential at times, particularly towards the far South, where the GFS UK Precipitation chart shows some high accumulative rainfall in that area. Perhaps also accompanied by the odd rumble of thunder. Further North towards North-Western areas of the British Isles and conditions look to be more showery. It will feel quite cool under the rain to the South with temperatures into the low and mid teens. Generally a little warmer over Northern UK and Ireland with temperatures in the mid to high teens, although Northern Scotland could see similar temperatures to those to the South of the UK.

Friday Night and Saturday Morning - as the Southern UK Low Pressure system pulls away into the North-Sea, it will pull in a breezy North-Easterly flow over the UK. The rain becoming increasingly confined to South-Eastern areas. Drier everywhere else with a chilly night in store for North-Western British Isles - temperatures getting into single digits in those parts, especially under clearer skies. Perhaps even chilly enough for a slight frost over hilly parts of Western Scotland. Milder to the South and South-East of the UK, particularly under the cloud and rain.

Saturday - it's game over for the rain to the East of the UK and it's now playing hide-and-seek in the North-Sea! It should generally be more of a calmer day as a ridge of High Pressure builds over the South-West/South of the UK. Some showers are possible, though, with the worst of these looking to be towards the North-East of the UK. But that ridge of High Pressure to the South-West of the UK should help to keep the weather mostly dry and bright in that area. With the pressure looking quite slack, it shouldn't be too windy, especially inland. Compared to Friday, Southern parts should see a warmer day. Temperatures perhaps reaching the 20*C mark in the far South, in particular in sunny spells. Cooler the further North of the UK you go with temperatures into the low-teens in Northern Scotland.

Later on in the day, an Atlantic Low to the West will bring some wind and rain East into Ireland. Drier and chillier elsewhere, especially over Northern UK. Temperatures perhaps getting close to freezing in some parts of Eastern Scotland. Quite incredible, really, should the GFS be projecting those temperatures correctly. Milder over Ireland, more so towards the South of the country, and also towards the South-Western UK. Low to mid-teen temperatures possible in the far South-West.

Overall, some rather action-packed weather for places. Nothing super-warm likely (if it's the type of weather you're after) and the nights, this being more the case the further North you are, will be chilly.

[johnholmes]

Interesting the difference GFS to Met forecast for here

Met=Prob slight rain for 1-2 hours in evening

GFS shows 10mm Friday into Saturday

!!

[BlueHedgehog074]

Interesting the difference GFS to Met forecast for here

Met=Prob slight rain for 1-2 hours in evening

GFS shows 10mm Friday into Saturday

!!

Will be amusing to see which model/forecast gets tomorrow's rain closest to the mark. I think the GFS is possibly over-doing it a bit, though. I suppose it's just like with thundery weather sometimes - even just 12 hours away before the main event, differences in the intensity and distribution of storms on each of the models and forecasts can be striking!  

[Frosty.]

Out of the 12z runs so far, the GEM 12z gets my vote with a change to more generally settled and pleasantly warm conditions through early August with the potential for high pressure to hang around for a while with the PFJ further to the nw.

As for the gfs 12z, next week shows a cool mixture of sunshine and showers, some heavy with hail and thunder, especially down the eastern half of the UK, then the s/e become fine and warmer with high pressure close to the south/southeast before another trough swings down from the north west bringing a return of cool and unsettled weather to all areas.

Edited July 23, 2015 by Frosty.

[Man With Beard]

The problem for the Azores High on ECM T168 is seen far to our north:

 

There is a block there, and it is in danger of preventing low pressures from the Atlantic taking a more northerly path. As a result, any pressure build towards the UK is squeezed out:

By T240, the block has pushed the trough back towards the UK.

 

It is very true that the ECM can overstate blocking at times, and for any chance of a turnaround at the months end, it really is necessary for this block to be over-exaggerated too. But even if it is, the road back to settled weather from the current position seems rather long and hard right now.

[mb018538]

Yes desperate ECM tonight, which rather than erodes the Greenland block, builds it up to 1040mb! If things follow this pattern, we could be seriously running out of time for some real heat!

[knocker]

The NOAA 8-14 and the GEFS anomaly at T360 although not identical, (one wouldn't expect them to be) they both retain the weak upper trough and a W/NW flow and no sign of anticyclonic activity. Need to see what the ECM comes up with but at this rate the expected settled weather need be put back a tad.

 

The NOAA discussion

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOUT AVERAGE, 3 OUT OF 5, DUE  TO REASONABLY GOOD AGREEMENT AMONG MODELS ON THE 500-HPA CIRCULATION PATTERN,  OFFSET BY THE EXPECTATION OF RELATIVELY LOW AMPLITUDE FLOW.  

Edited July 23, 2015 by knocker

[johnholmes]

The NOAA 8-15 gives no real hope for any prolonged surface pressure rise close/over the UK from that 500mb pattern, nor as a result any marked heat of any duration. It takes us out to 6 August. To me I would be surprised if the pattern changes markedly within 5 days or so from that date.

Hopefully I will be wrong for those of us wanting some summer heat and sunshine in August.

[mushymanrob]

The NOAA 8-15 gives no real hope for any prolonged surface pressure rise close/over the UK from that 500mb pattern, nor as a result any marked heat of any duration. It takes us out to 6 August. To me I would be surprised if the pattern changes markedly within 5 days or so from that date.

Hopefully I will be wrong for those of us wanting some summer heat and sunshine in August.

That would take us to mid August with only a couple of weeks left of summer.... Well i was wrong, i sincerely expected something of a hot spell especially after the hot blip earlier this month. For me, by then, its over.

[knocker]

The ext ECM anomaly tonight doesn't make good viewing either with troughs eastern Europe and slap over the UK with no indication of height rises and maintaining the westerly flow. Be interesting what the EC32 makes of this.

Edited July 23, 2015 by knocker

[Cloud 10]

The negative AO/NAO does seem rather reluctant to give way at the moment,and as already mentioned in a couple of recent posts this keeps the jet on a more Southerly track,with any ridges of high pressure being very transient.

 

[A Frayed Knot]

I see High Pressure Building in the Atlantic for August And Spreading SW . Looks a Dream and it ain't in FI .

[knocker]

The latest EC32 update is pretty reasonable considering recent weather.

 

By the 5th August still a weak upper trough to the NW which may affect the N otherwise general influence from the Azores ridge in a cool westerly flow.

 

For the next week until the 13th less influence from the trough and the whole of the UK in a weak westerly flow from the Azores HP lying to the SW with temps around average and quite dry.

 

This scenario essentially remains the same until the 24th with the weak trough to the north possibly impinging on Scotland on occasion otherwise the Azores HP firmly planted to the SW continuing the weak westerly, cool with temps just below average and certainly little precipitation.

 

Summary

 

No sign of any significant  HP build over the UK or to the east but from the 4th until the 24th the Azores appears to hold sway bringing a weak westerly flow with the upper trough a very weak affair so if this turns out to be anywhere near the mark it could be a lot worst. Certainly no sign of hot weather but perhaps sunny and dry is the best we can hope for.

Edited July 24, 2015 by knocker

[bluearmy]

I think that's quite a positive interpretation knocks. With Europe staying generally warm to our se and the Atlantic uppers cooler than usual, the jet seems likely to hold sway for us, exposed between the two battling air masses. I would say more of the same with the nw/se split the best case scenario. otherwise, more generally unsettled than we saw through July.

Of course, this is just one run. the general extended ens promise of persistent height rise from the sw into headed ne as we head into August seeming to evaporate with each passing 12 hours.

Let's hope the models are underplaying developments upstream which will revert the modelling back in that general direction. It wouldn't take too much for the whole thing to become more sw/ne and us to come under the euro heights rather more.

[mushymanrob]

The latest EC32 update is pretty reasonable considering recent weather.

 

By the 5th August still a weak upper trough to the NW which may affect the N otherwise general influence from the Azores ridge in a cool westerly flow.

 

For the next week until the 13th less influence from the trough and the whole of the UK in a weak westerly flow from the Azores HP lying to the SW with temps around average and quite dry.

 

This scenario essentially remains the same until the 24th with the weak trough to the north possibly impinging on Scotland on occasion otherwise the Azores HP firmly planted to the SW continuing the weak westerly, cool with temps just below average and certainly little precipitation.

 

Summary

 

No sign of any significant  HP build over the UK or to the east but from the 4th until the 24th the Azores appears to hold sway bringing a weak westerly flow with the upper trough a very weak affair so if this turns out to be anywhere near the mark it could be a lot worst. Certainly no sign of hot weather but perhaps sunny and dry is the best we can hope for.

 

i think the 8-14 day anomaly chart isnt far from supporting that (and is just outside that timeframe), so lets see if over the next week or so it moves in the right direction... without heat, ill settle for dry.

[knocker]

I think that's quite a positive interpretation knocks. With Europe staying generally warm to our se and the Atlantic uppers cooler than usual, the jet seems likely to hold sway for us, exposed between the two battling air masses. I would say more of the same with the nw/se split the best case scenario. otherwise, more generally unsettled than we saw through July.

Of course, this is just one run. the general extended ens promise of persistent height rise from the sw into headed ne as we head into August seeming to evaporate with each passing 12 hours.

Let's hope the models are underplaying developments upstream which will revert the modelling back in that general direction. It wouldn't take too much for the whole thing to become more sw/ne and us to come under the euro heights rather more.

 

Oh I agree it's a finely balanced situation and wouldn't take much to topple it one way or tother. Need to keep an eye on the professional guidance.

[knocker]

One forecast upstream pattern change for next week

Charts weatherbell

 

[johnholmes]

well the ray of hope that the GFS anomaly chart showed yesterday has all but disappeared this morning. This puts us back at, unless the NOAA 6-10 decides to up the odds this evening, to at least 15 days from now for no marked increase in ridging let alone any long term heat.

I think that the best that may occur 2 weeks or so down the line is that some kind of upper ridge in the Atlantic may develop to give drier conditions all round for the UK but with some temporary blips as weather systems run around its northern flank. Thus the south will fare best with more days of dry weather and a higher level of temperature anomaly at the surface than further north. To me there is little if any indication of an early even mid August heat wave that some seem to be suggesting.

anomaly link for EC-GFS this morning

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

Edited July 24, 2015 by johnholmes

[phil nw.]

well the ray of hope that the GFS anomaly chart showed yesterday has all but disappeared this morning. This puts us back at, unless the NOAA 6-10 decides to up the odds this evening, to at least 15 days from now for no marked increase in ridging let alone any long term heat.

I think that the best that may occur 2 weeks or so down the line is that some kind of upper ridge in the Atlantic may develop to give drier conditions all round for the UK but with some temporary blips as weather systems run around its northern flank. Thus the south will fare best with more days of dry weather and a higher level of temperature anomaly at the surface than further north. To me there is little if any indication of an early even mid August heat wave that some seem to be suggesting.

anomaly link for EC-GFS this morning

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

 

Not looking great for UK Holidaying in the next 2 weeks John,that's for sure.Yes there will be some dry days with some warmth from the sun but modelling shows we are well short of any real mid Summer heat.

The ECM for next week at T120hrs is really typical

 

extensive cooler air across the N.Atlantic and NW.Europe incl.the UK

 

The GFS surface temp forecast for here in C.England shows forecasted max's struggling to even reach average levels.

 

Ok some days for more active outdoor activities maybe but a lack of higher temperatures may well deter beach lovers.

Not a very cheerfull view from me for Summer lovers i am sorry to say but it is what it is.

[BlueHedgehog074]

I don't really want to over-hype the weather possibilities for the end of next week, but looking at some of the various operational models and some of the ensembles around the 168 to 240 hour range and I feel there is some reasonable support to see some pressure rises over the UK and perhaps to our East/North-East into the continent:

Just looking at the 06Z GFS first from 192 hours and it shows quite a decent build of pressure over the UK from our South-West in the Atlantic. This of which then migrates to the East of the UK into the continent drawing up some warm and bright weather over the UK from the South. Eastern and South-Eastern UK areas, in particular, would probably benefit the most from the sunniest and warmest conditions:

The 00Z ECMWF (using the 168 to 216 hour time-frames) showing similar ideas with High Pressure extending its ridging North-Eastwards over the UK from the South-West. This, again, migrating to the East of the UK. The High Pressure is, however, not as strong as that on the GFS - the pressure looks a bit messier and the heights at the 500mb level are a little less strong. Nevertheless, it would lead to some settled and warm conditions for places, particularly towards the Eastern part of the British Isles.

Support also from the 00Z ECMWF ensemble mean to see pressure building over and to the East of the UK from our South-West. Perhaps not a super strong signal as, just like on the ECMWF operational run above, the pressure doesn't seem too strong. but I think still enough of a signal to suggest areas of High Pressure will become increasingly influential around the British Isles area towards the beginning of August:

The 00Z GEM (using the 168 to 216 hour time-frames again), though, is one of the less impressive operational models for a build of High Pressure over the UK. Stubborn troughing to the East of the UK towards Scandinavia prevents any meaningful build of pressure over the island and to our East and any true Azores High becomes locked away to our South-West in the Southern Atlantic. One thing that does seem evident, though, is despite the corridor of Atlantic Lows to our West and the troughing to our East, there is at least a small narrow belt of weak High Pressure over Western UK, together with a small ridge over South-Western UK, to prevent any real washout conditions occurring. Plus, South-Western areas would probably remain mostly dry and settled. And I think in that respect, it's bears a few odd similarities to the above models:

And while it is at 180 hours, the NAVGEM looks as though it would almost head in the same direction. Have, nevertheless, doodled on the chart to show the kind of things that would need to happen to draw the High Pressure to the South-West of us over, and to the East of, the UK.

The black arrow would show that troughing would need to dig far enough South in the mid-Atlantic to help encourage heights and pressure building North-Eastwards over the UK and into Mainland Europe. Additionally, the blue arrow, along with the blue circle (showing the trough of Lows to our North/North-East) would also need to clear far enough East towards Eastern (or perhaps central) Scandinavia, to enable the Azores High to fight its way North-East over the UK - indicated by the green arrow. That Scandinavian troughing can be a bit of a sneaky devil sometimes when it extends its low heights towards the UK plotting its revenge against any Azores High Pressure systems that dare enter the British Isles...

Another ideal situation would be simply seeing Lows out West linking up towards Lows to our East and orientating themselves in a South-West to North-East direction to our North helped by a Northerly tracking Jet Stream to give room for High Pressure to develop over the UK and into mainland Europe.

Taking a look at the 06Z GEFS air pressure ensembles for both London and Aberdeenshire, and signs for pressure rises look evident towards the end of the month from around the 31st July onwards. And though the lines become more scattered towards the end of both the graphs, there are perhaps enough hints that pressure may then start lowering somewhat from 4th August, which may mean this might not be a long lasting spell of possible High Pressure dominated conditions. More of a transient affair, perhaps. Despite being in deep Fantasy Island, the 06Z GFS operational model had showed the Atlantic and a more Westerly dominated pattern breaking through nearer to the end of its run. Having said that, even if this possible spell of more settled conditions doesn't last long, the ensembles don't generally show pressure dropping to especially low values, particularly for the London area. But it could mean more of a general South to North split could re-establish. Less unsettled to the South and more changeable to the North. Since it's far away, I wouldn't get too worried about it yet if you're wanting a long-lasting very warm and settled spell as that could easily change, plus I am just basing that on one set of GEFS ensembles:

Another thing to mention about those GEFS graph ensembles is the GFS operational model (green line) is more at the higher end of those ensembles during that pressure rise at the beginning of August, which may mean the GFS operational model is possibility slightly over-doing the build of pressure for that period.

One other thing to note about these GEFS air pressure ensembles is that, for the Aberdeenshire graph in particular, some of the ensembles members go for a notable dip in pressure between the 29th July and 1st August.

This is highlighted well in the GEFS postage stamps below (for 168 hours) where a few of the ensemble members (perturbations) showing Low Pressure to the North or North-East affecting Northern parts:

This possibly explaining why some ensembles members go for a brief dip between in pressure within that period. Since the GEFS ensemble mean, the control and the main GFS operational don't go for much of a dip in air pressure in that period, it is possible that some ensembles members are just exaggerating the dominance of Low Pressure, most particularly for Northern UK, in that space of time.

Lastly, while the ECMWF/GFS 6 to 10 day mean chart below doesn't look all that encouraging for major height rises over the UK - the GFS one (to the right in the below image) in fact looks quite Westerly dominated - I think it would still be fair to say it doesn't look like any real washout conditions are likely either. Especially for the South. None of them show any deep troughs influencing the UK - the anomalies over the UK area look neutral. The ECMWF version does at least show a 'bump' in the 500mb flow over the UK with ridging quite likely. More of a warmer looking chart as well with the upper flow from the South-West influencing the UK.

Edit: only just noticed the above posts, particularly that from John Holmes, who to be fair has a lot of experience using these types of mean charts, and I think his interpretation is more fairer with the idea of the South seeing the best of the less unsettled conditions and the North being more influence by areas of Lows to the North.

I think it will be quite fascinating seeing the latest NOAA 6 to 10 day anomaly chart update tonight to see whether it shows a clearer signal for heights rises and pressure building towards the North-Western Europe area.

While there are still some good reasons to be cautious of possible build of High Pressure towards our part of the world next week along with possible less disturbed and more widespread settled spell developing (especially for the South and East), I feel it's possible that Glacier Point may just be on to something when he suggested the possibility of a settled and warmer spell occurring...

If I could interject here....

The upper level divergence signal in the Indian Ocean (MJO related) is slowly edging across the Indian Ocean towards the Tropical Maritimes. That is a region where the GEFS frequently struggles and shows negative bias, so given the importance of this tropical driver, I would not be in a rush to back the GEFS means here - this is not the model to show us out of next weeks rather large trough dominating north and north-west Europe.

With the tropical signal migrating through the Indian Ocean, we should see a fall in pressure to the east of the Himalayas and pretty rapid spike in tendency in relative angular momentum and the Global Wind Oscillation move towards phase 4. That's a decent signal for Rossby wave influence for rising pressure over NW Europe within a 10-15 day timeframe.

EC EPS 00z going for a pretty impressive turnaround in pressure end next week into the following week, with the longwave trough replaced by a moderate strength +ve height anomaly centred to our east. So much more settled and becoming warmer again in the extended outlook period.

Hopefully, for the warm and settled weather enthusiasts, this is the sort of direction some of the models keep heading in and that the support for it increases further.

(Xtra info: just a quick look at the latest GFS run and it seems to be heading in a similar direction to the previous run, although the Low(s) over Northern may need watching...)

Edited July 24, 2015 by DiagonalRedLine

[phil nw.]

Just a heads up- a few posts have been moved to the other Model thread,where they seem more suited.

Edited July 24, 2015 by phil nw.