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Model output discussion - summer rolls on


Paul

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

To me it look like next week shows much cooler and more changeable conditions are on the way from the w / nw, even the SE feels it by the second half of next week..for the NW you could even call it autumnal..unless I'm missing something?...there's good support from the gfs / ukmo for this to occur, and the gfs looks even cooler and more unsettled by week 2..will it be right.?.I have no idea but just saying what's currently being shown!☺

Edited by Frosty.
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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

The GEFS 12z mean clearly shows a change to cooler more changeable atlantic conditions during next week and beyond, the s / se not desperately cool or unsettled but low 20's c which would be way down on what the s / se has become used to this summer so far but the further n / nw you are it looks much cooler and more unsettled, you could even call low teens celsius autumnal by august standards..there are then hints that the azores high might ridge in again just beyond mid august.

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

Interesting discussion in here tonight, while the middle of next week is looking unsettled, the latest runs at T192 are bringing the high pressure back at least for the south.  Here FV3 and ECM 

image.thumb.jpg.031eb6b53672f590bb35b29267c56341.jpg

image.thumb.jpg.cf498c3f7fc8db7efc30efa41a3ad460.jpg

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

On to T240, those runs diverge with the ECM looking to push the high pressure in still, and the low slowly clearing:

image.thumb.jpg.6f19324460f3e4a1ccc0a2213226b9e6.jpg

The FV3 goes off the rails (in my view) with heights towards Greenland, actually at T234:

image.thumb.jpg.eb2df34db8166d06b4851b1f58cab25e.jpg

These charts are obviously day 8-10, the message is summer is not over, and my expectations are actually something a little more positive than the ECM run to be the actual weather.  We'll see.

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

The Ecm 12z certainly shows some unseasonably cool and unsettled weather on the way.

ECM1-144.gif

ECM1-168.gif

ECM0-168.gif

ECM1-192.gif

ECM0-192.gif

ECM1-216.gif

 

ECM1-240.gif

ECM0-240.gif

Edited by Frosty.
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11 minutes ago, Singularity said:

The point is that the signals offer greater predictability that enables a more confident idea of what will happen 'behind the scenes' of the charts that the models throw at us. When AAM is in GWO phase 3 and ENSO is in a supportive state for a climb in that AAM, there's a very high probability that the atmosphere will then, over the following 2-3 weeks, exhibit an El Nino-type cycle of events.

Mid-summer onward, this takes the general form of:
1. A ridge moving across the UK, and a trough moving down near the Azores.
2. That ridge moving to be E or NE of the UK, with the trough out west getting closer, this combination bringing a high potential for 1-3 day plume type events with sometimes thundery breakdowns.

Then, there's a wider variety of possible outcomes, this relating back to the ENSO state.

El Nino outcome (the descending part of the cycle is limited and then a new climb in AAM kicks in): The trough moves off to the N, NE or E after 1-3 days, often with some form of secondary low on the SE then E flank, with a new ridge of high pressure building across afterwards, this aided by a new movement of a trough toward the Azores.

La Nina outcome (the descending part of the cycle is large enough to move AAM into negative anomaly territory, with the next AAM rise a lot further off in time: There's no new trough into the mid-Atlantic, instead a ridge builds. The Atlantic jet as a free run across the UK, and the trough that interacted with the heat plume is able to strengthen while still near or over the UK, often with further lows arriving from the Atlantic to sustain the unsettled conditions for longer.

Neutral outcome: somewhere in between the above two... in this situation we have less predictability to work with, but please note that you can have an El Nino atmospheric state even when the oceanic indices are neutral, as is the case at the moment.

 

If you look at events from last Friday through to now, you can see that steps 1 and 2 have played out with the El Nino outcome then following swiftly on.

Just imagine averaging the charts out across that period. You'd see only weak mean ridge and trough patterns, as if there wasn't a significant relationship, in that way masking the true situation. It's like a sequence of numbers that went 1, 3 ,5 ,7 ,5 ,3 ,1. What does the overall mean of 5 really tell you there about the behaviour and pattern? Not much. You can only tell that it went all the way from 1 to 7 and back if you look at small enough step-intervals.

 

Currently, the anticipation by the likes of Tamara and I is that the same broad sequence will play out again, starting with the plume breakdown next Tue/Wed/Thu, but the modelling is generally showing the follow up tot step 2 to be more of a La Nina outcome. Hence the cognitive dissonance caused by model charts that feature a big ridge in the Atlantic next Thu/Fri onward. For this reason, of the 12z runs, GEM is the least suspicious looking as a new trough establishes itself out west of the UK, and GFS the most so with its Atlantic ridge and troughs diving into the UK from the northwest. ECM sits in between, and isn't that much in the way of adjustment from being the most credible of the 12z runs.

I must stress that this is not, therefore, an anticipation of an overall settled August; continued Nino cycles will support a continued sequence of settled spells, plume-affected spells and breakdowns that may be thundery followed by unsettled interludes. We've well and truly left the setup of June and much of July behind. 

 

I hope this makes sense, or at least as much as it can for such a complex approach. After all, I'm a specialist in weather and climate science, and it took me around half a decade of reading and re-reading to get my head around it enough to be able to discuss it without the world's biggest caveat looming over my words!

Sounds completely ideal and similar to August 2004

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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
16 minutes ago, Leo97t said:

Sounds completely ideal and similar to August 2004

Absolutely; it's a good match from the GSDM perspective, as AAM was entirely in the positive anomalies that month, with the GWO showing orbits through phases 5 to 8 and then back round again, making for two Nino-like cycles between 1st and 31st. 

Not to say that the details will be the same this time around, but the overall theme of the month should be.

Edited by Singularity
Still Only Human
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Posted
  • Location: Cleeve, North Somerset
  • Weather Preferences: Continental winters & summers.
  • Location: Cleeve, North Somerset

Surely an August 2004 setup would be very warm and humid though. After next Wednesday, we seem to get the opposite - cooler northwesterlies move in, which would actually be a lot drier but much less seasonal?

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
17 minutes ago, Leo97t said:

Sounds completely ideal and similar to August 2004

And, as it's all occurring after umpteen days/weeks above 25C, there's plenty of scope for things to get 'cooler' without actually getting cool?

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Posted
  • Location: Camborne
  • Location: Camborne

They hope not similar in Boscastle

August 2004

The averaging period used for the following assessment was 1961-1990.

UK overview

A very wet month, with many areas receiving double their average August rainfall. Sunshine totals were close to average in most parts, although parts of south-east Scotland and north-east England had considerably lower than average amounts. Shetland's sunshine total was much higher than average. Mean temperatures were generally one or two degrees Celsius above average.

On 16 August, there was devastation in Boscastle (north Cornwall) due to severe flooding, and at nearby Otterham 200.4 mm of rain fell in 24 hours. Lesnewth near Boscastle had 64.8 mm of rain in an hour. Eskdalemuir recorded over 300 mm during the month.

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

Super post by @Singularity above, for someone trying to properly understand the GWO it clarified a few things for me. 

ECM 12z ensemble mean, here at T216, supportive of a reintroduction of high pressure from the SW, no sign of a horrid trough settling over the UK, but would need to see the individual runs or clusters to be sure.  

image.thumb.jpg.07974e899e648a3c1d4ed991bfa04a39.jpg

I firmly expect the model output to improve re fine summer weather in the 0z and 12z tomorrow.  And to @Quicksilver1989 who brought it up^^^^^^^^, I still think there's a cat in hell's chance of the jet stream significantly breaking through directly over the UK in August!  ?️✔️.  Happy to be proved wrong as always.

Edited by Mike Poole
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Posted
  • Location: Kirklees, West Yorks
  • Weather Preferences: Winter
  • Location: Kirklees, West Yorks

The ecm shows a breakdown to cooler weather mid week and hints of a pressure rise at latter end of the run. Not a bad run really. I think people are struggling to come to terms with potential unsettled and cool blips after the last few extroadinary months. But that pattern from june and july has shifted and done with and that be the same with teleconnections. Im not saying this doesnt imply settled and hot spells for the rest of the month. Im just saying the patterns have shifted from the extremely dry nature that we saw in may, june and most of july, to something more normal if you can put it like that. The teleconnections are shifting different mixes and terriotries, which would take away the abundance of constant weeks of dry and warm weather, to a pattern more prone to unsettled blips making incursions from time to time. I think other posts like @Tamara and @Singularity may know what im getting at. Thats how im understanding it at the minute. My knowledge on background signals etc isnt quite vast

Edited by Snowjokes92
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Posted
  • Location: Kirklees, West Yorks
  • Weather Preferences: Winter
  • Location: Kirklees, West Yorks
1 minute ago, Man With Beard said:

Well whether there are future plumes or not, I think tonight's runs have finally put the lid on chances of "the big one" for this year, by that I mean an extreme heatwave reaching 36C to 40C. A lot of the ingredients have been in place the past two weeks - exceptional heat over Iberia, high sea temps, dry ground, heat already in situ, Scandia ridging and a more active Atlantic coming against it. Alas the Scandi ridge has fallen just a couple of days too soon. Might be another decade before we get as good a chance. Still I imagine some of you are very relieved! :)

I agree about the scandi ridge as brilliant as it is, but definetly looking like it will fall for now. But like i said previously, teleconnections and back ground signals and developing el nino, are defonetly going to change from what we have had the last few months. Which is why i said, i think we will be more prone to more unsettled and variable weather in between at the very least.

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Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK

Depends what level of ENSO we get. Either way, the link isn’t concrete for winter weather in the UK. Fascinating all the same.

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4 hours ago, Weather-history said:

Not a lot of rain for the south on that GFS 12 op run. Out to a week on Saturday

GFSOPUK12_219_18.png

There wasn’t a lot of forecast for here 3 days before last weekend and we ended up with 25mm on Sunday alone.....

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

Nothing summery about these charts from tonight's Ecm 12z ensemble mean...quite a change on the way next week  with much cooler more changeable atlantic weather spreading across the uk, especially for the n / nw..hot early next week for the s / se.

EDM1-144.gif

EDM1-168.gif

EDM0-168.gif

EDM1-192.gif

EDM0-192.gif

EDM1-216.gif

EDM0-216.gif

EDM1-240.gif

EDM0-240.gif

Edited by Frosty.
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Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl

Gosh not had such in depth posts in an evening for a long time - more like winter in here tonight - a refreshing change, from weeks of well not much to discuss, all suggesting a notable change on the way.

As others have said we are now firmly moving out of the dominant exceptionally warm dry pattern we have had since mid April, and something more typical at least for the time of year - its August, and the atlantic is ramping into gear.. the usual NW-SE split is firmly taking hold, the SE holding on to summery conditions, the NW more prone to unsettled cooler weather.

The models are moving the trough through the UK next week, ushering in a spell of unsettled weather for all, and cooler, but probably staying fairly warm in the SE still.

A large ridge is then shown to develop in mid atlantic, yet others more knowledgeable than me, suggest the El Nino background won't be supportive of low pressure in succession scenario flattening the ridge, but instead another sharp trough development with plume scenario, so expect perhaps a change in the models next day or two suggesting another nosing of the azores high as we approach mid month, and likely shortlived plume again, before the trough crashes in.

This is a decent pattern for the SE, but unfortunately not the NW, August could end up being a generally good month in the SE, but a poor one in the NW - as often seems to occur.

 

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Posted
  • Location: Powys Mid Wales borders.
  • Location: Powys Mid Wales borders.

I certainly can`t see no august 2004 that was a one of a kind and the most memorable thundery augusts on recent and ex tropical storms included.on a southerly jet.

A lot of interest continues as this summer unfolds with the model output currently as the form horse august in recent years goes downhill rapidy with the atlantic coming in.

But this is no ordinary summer as we are looking at the driest and hottest possible summer since the famous 1976.

Anyway the change comes midweek again.

Rtavn1441.gif

 

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Posted
  • Location: NR Worthing SE Coast
  • Location: NR Worthing SE Coast
1 hour ago, Frosty. said:

Nothing summery about these charts from tonight's Ecm 12z ensemble mean...quite a change on the way next week  with much cooler more changeable atlantic weather spreading across the uk, especially for the n / nw..hot early next week for the s / se.

EDM1-144.gif

EDM1-168.gif

EDM0-168.gif

EDM1-192.gif

EDM0-192.gif

EDM1-216.gif

EDM0-216.gif

EDM1-240.gif

EDM0-240.gif

Guess the end of the amazing summer had to come  to an end some time  Frosty,Having said that sill a possibility of hot conditions returning after Mid month,looking at various model output and the met office forecast using their seasonal computer models.Im also intrigued by this winter coming,IF we get  bitterly cold continental air crossing the above normal SST in North Sea ,that would lead to huge convective snow showers moving in from the E,still that’s in the future lol,still turning hot over the weekend and early next week.

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Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK

I'd be wary about writing the summer off just yet! It looks nailed on that once we get to Wednesday next week the hot weather will be moved away by low pressure for a time. However, it doesn't look desperately unsettled - and by no means a wash out. ECM ensembles & met office long ranger still going for something more settled as we head through August. To be honest, even if the rest of August didn't offer much, we've still had another week of temperatures in the high 20s/low 30s....which beats most of the terrible August months we've had in recent years regardless. What a summer!

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