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Model output discussion - summer rolls on


Paul

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

They key to any certainty is consistency - and when the ensembles split so much at only 5 days away like they are at the moment, you just can't forecast anything and be sure about it.

We could still end up with anything from just warm weather to something exceptional (35c+) again just after the weekend. Loads to sort out! It's like being here in winter!

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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire

I personally can't see a major plume affecting the UK (bar the south east) in the next week. A little like the weekend just gone, the Icelandic low is exerting too much influence in our neck of the woods to prevent any major plume engulfing the UK. An incredible summer thus far. Persistent cloud has been troublesome this week though. 

Edited by blizzard81
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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

I wonder how confident NOAA are in that anomaly plot from two days ago now... 

 

Silly jibes aside, the anticipated trend showing its hand a little this morning; a slowing down of the Atlantic trough, leaving the 'heat low' in place for longer to our south, so increasing the potential for the mega-plume to find its way in via France/Germany/Belgium.

This outcome requires a more prolonged draw to threaten us with dangerous levels of heat, in contrast to a draw from the south which is quicker and more intense but tends to break down sooner anyway. 

The thing about next week though, as that we have a different direction of trend being encouraged by the teleconnections - last time it was toward a greater eastward push of the Atlantic trough due to the conclusion of the last tropical cycle, but this time it's toward a weaker push with the trough staying further west. At this stage it's impossible to be sure how far this might go, but that GFS 00z run comes very close to keeping it far enough west that the 'heat low' doesn't get a chance to escape NE until at least next weekend. In fact I think it would have got there had it not failed to bring another Atlantic trough into play with the Azores High being shoved NE again (still waiting for that next stage to be 'realsied' by the models).

This potential might yet be taken down in a different way to the too-progressive Atlantic trough outcome though - that trough could instead dig down west of the UK a bit, with the 'heat low' moving right up through the UK on a near-northerly path. Another way to arrive at the quicker, more intense but shorter-lived result. The ECM 00z comes quite close to this outcome; it was just a little too progressive with the Atlantic trough.

 

Given all the above possibilities, it's no wonder that the ensembles are well scattered at the moment. Still at least a couple more days until we have a good idea of what happens Monday onward, I reckon.

Oh and - UKMO, forgot about that one! That's actually only a stronger ridge away from a gentler, more easterly variation of the trapped 'heat low' scenario. It would likely become hot for a number of days, but not dangerously so.

Edited by Singularity
UKMO
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Posted
  • Location: chellaston, derby
  • Weather Preferences: The Actual Weather ..... not fantasy.
  • Location: chellaston, derby
58 minutes ago, Singularity said:

I wonder how confident NOAA are in that anomaly plot from two days ago now... 

 

 

still on 5/5, very good agreement. it wasnt so much the noaa's that were inaccurate as much as my interpretation of them that was in my post..

they still show a moderate westerly upper flow, but have dropped the idea of a weak ridge to our west somewhat. so detail aside, theres no strong ridging or troughing over the uk on either the 6/10 day (5/5 confidence) and the 8/14 day (4/5 confidence) period . i dont see anything in any model run that would really contradict this as any ridging or troughing in the 6-14 day period isnt expected to last long in a steady westerly upper flow. but please note, most of the coming ridging is occurring before the time period these charts cover. IF , and atm its a big 'if', the current ecms ridging off the atlantic is to become reality, the noaa's will pick it up. for now, id suggest the gfs 00z is pretty close to the conditions id expect , so not bad at all.

 

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

Looking likely that there'll be at least one less settled day at the end of next week according to EC ensembles this morning - EC op run not with much support. 

A very mixed bag from the clusters in the D11-D15 period. Probably a temporary recovery but by D12 we have this... no discernable guidance really, a bit like yesterday. 

ec-ens_nat_z500scenarios_2018080100_300.

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Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK
9 minutes ago, Man With Beard said:

Looking likely that there'll be at least one less settled day at the end of next week according to EC ensembles this morning - EC op run not with much support. 

A very mixed bag from the clusters in the D11-D15 period. Probably a temporary recovery but by D12 we have this... no discernable guidance really, a bit like yesterday. 

ec-ens_nat_z500scenarios_2018080100_300.

I just had a flick through them too - not really worth posting as you say, they pretty much have every option under the sun on offer in the 10-15 day period, so not much help at all. Maybe once this plume/non plume event has been sorted and gone by we will have a better picture. When the heatwave was in full swing we were getting 100% clusters even at day 10-15!

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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

There's some absolutely scorching weather on the Gfs 6z operational during the next week or so (reliable / semi-reliable timeframe) especially further s / se where temperatures get above 32c 90f at times..

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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire
54 minutes ago, Man With Beard said:

Looking likely that there'll be at least one less settled day at the end of next week according to EC ensembles this morning - EC op run not with much support. 

A very mixed bag from the clusters in the D11-D15 period. Probably a temporary recovery but by D12 we have this... no discernable guidance really, a bit like yesterday. 

ec-ens_nat_z500scenarios_2018080100_300.

Many thanks, as always for posting these mwb. Some uncertainty as you say but it's got to be said that the clear majority have the scandi trough and ridging to our west. This would result in a marked cool down as we enter the second third of August. Those wise words of Tamara appealing to all not to take each suite as gospel are resonant in my ears. However, it is very notable that the gfs ens agree with this marked cool down so it would be reasonable to suggest that both ecm and gfs are barking up the right tree. 

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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire
14 minutes ago, Frosty. said:

There's some absolutely scorching weather on the Gfs 6z operational during the next week or so (reliable / semi-reliable timeframe) especially further s / se where temperatures get above 32c 90f at times..

Not saying it won't happen but it's got to be said that the gfs 06z has a reputation, shall we say, of wanting to entertain with the extreme possibilities. It does the same in winter with it's almighty cold teases. 

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Posted
  • Location: Saltdean,Nr Brighton,East Sussex,Hither Green,SE London.
  • Location: Saltdean,Nr Brighton,East Sussex,Hither Green,SE London.
5 hours ago, blizzard81 said:

Not saying it won't happen but it's got to be said that the gfs 06z has a reputation, shall we say, of wanting to entertain with the extreme possibilities. It does the same in winter with it's almighty cold teases. 

Hardly an "extreme possibility" when most of the other models and Met office have been singing from the 06z hymn sheet for a few days now!

Edited by Polar Maritime
To move discussion on.
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Posted
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.

Let's please move on to discussing the Models, Thanks.

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

gefsens850london0.png

Still a plethora of options on the 6z ensemble - lots of very hot 15-20c members, but it has to be said a marked cool down looks likely after.

No ppn spikes really appearing, so dry and mainly settled looks the order of the day, but it's the first extended run of mean 850s below 10c that we've seen in a long time. Could be some very pleasant weather for those wanting a break from the incessant heat of this summer.

Edited by mb018538
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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

Looking at the GEFS 6z mean, the next week or so indicates predominantly very warm / hot weather across most of england and wales, especially further s / se with plenty of dry and sunny weather but an increasing risk of the high temperatures sparking some heavy showers / thunderstorms later. Beyond that there is a less warm trend as winds become w / nw'ly with temperatures returning closer to average but of course that range can easily change and the reliable timeframe shows plenty of heat for the s / se.

Edited by Frosty.
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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire

Gfs and ukmo now moving towards ecm. Warming up over the next few days, then a steady cool down. Azores then ridging in. After that? Who knows?

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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 ukmo 12z shows plenty of high pressure / strong ridging, especially further south and becoming hot across the s / se with temperatures into the low 30's c and widely mid to upper 20's c across most of england and wales, significantly cooler across northern uk, especially the far n where it also looks more changeable as weak atlantic frontal systems brush around the top of the high / ridge. By T+144 there is plume potential further south with a hot and humid continental air mass and a higher risk of thunderstorms from france and homegrown. 

UW24-21.gif

UW48-21.gif

UW48-7.gif

UW72-21.gif

UW96-21.gif

UW120-21.gif

UW120-7.gif

UW144-21.gif

UW144-7.gif

Edited by Frosty.
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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

@johnholmes sorry if I enraged you there, it was not intended as I was being silly - hence the use of the word - by referring to their charts from 2 days ago instead of today's ones, which have altered the orientation of the positive anomalies in a way that tones down the suggestion of mid-Atlantic ridging. The only thing that bugged me a couple of days ago was their level of confidence despite the uncertainty associated with background forcing - it would be respectful of that to set confidence at a 3, maybe 4 at a stretch.

 

Moving on - interesting developments from the GFS 12z for next Monday compared to the preceding run (or indeed few runs):

h850t850eu.png h850t850eu.png
hgt300.png hgt300.png

The trough is elongating more toward the Azores on the 12z run right) compared to 06z run (left). Granted, it doesn't reach anywhere near that region, but the fact it's reaching down further west than before is sufficient to allow more time for pressure to rise across Scandinavia Mon-Tue.

On this particular run, the jet is a lot stronger due to the low having been flatter in shape during Sunday (a bit counter-intuitive if you ask me...), but that need not have been the case. With the same jet stream strength as the 06z, I believe the cool polar maritime air would have continued south for longer, passing west of Iberia and bringing about a stronger Iberian trough development than we've seen modelled lately. That's a hotter and more thundery outcome to watch out for.

The UKMO 12z appears to have the weaker jet + trough digging further west combination I'm talking about. Much as the 00z run did, to the model's credit.

Rukm1441.gif

Still time for further westward adjustments to where the trough digs south, but thundery spells are a fit to the Nino background in August, so I'd be surprised if we didn't see anything thundery for at least part of the UK after next Wednesday at the latest.

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

Not impressed with any of the 12s so far in the reliable from a decent summer weather point of view, GEM the worst for sure, here T180:

image.thumb.jpg.14dbbab86146dbb8c28dd0404156669c.jpg

ICON poor, not convinced about UKMO, GFS a bit meh! 

Kind of cancels out morning runs so a no-score draw is the verdict from me on the day, more runs needed, let's see what tomorrow brings. This story is not over.

Edited by Mike Poole
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Posted
  • Location: Maldon, Essex
  • Location: Maldon, Essex
3 minutes ago, Mike Poole said:

Not impressed with any of the 12s so far in the reliable.  GEM the worst for sure, here T180:

image.thumb.jpg.14dbbab86146dbb8c28dd0404156669c.jpg

ICON poor, not convinced about UKMO, GFS a bit meh! 

Kind of cancels out morning runs so a no-score draw is the verdict from me, more runs needed, let's see what tomorrow brings. This story is not over.

You mentioned the reliable, then posted a T180 chart!

I would say anything past 120 is very uncertain.

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Posted
  • Location: Peterborough
  • Weather Preferences: Snow and frost in the winter. Hot and sunny, thunderstorms in the summer.
  • Location: Peterborough

Day 5 charts

UKMO/GFS/GEM

UW120-21.GIF?01-18   gfs-0-120.png?12   gem-0-120.png?12

The GFS has a much deeper low compared to the other two and as such we do not see the high sheer off so a westerly flow for northern areas as opposed to the light continental flow seen on the other two.

Day 6

UW144-21.GIF?01-18   gfs-0-144.png?12   gem-0-144.png?12

Again the GFS and its deeper low does seems to want to push the trough cleanly eastwards and we see a fresher westerly develop during the middle of next week. The UKMO and GEM are starting to slow the eastward progress of that low down so not strong guidance as a developing cut off low that could form on either the GEM or UKMO could lead to a drastically different solution further down the line. The GEM parks the low over the UK but at that timeframe a similar evolution could lead to the low being further west which would allow a much warmer southerly flow to be maintained.

Not overly convinced going forward apart from up to next Tuesday there looks like being a lot of fine and dry weather with temperatures above or well above average with hot conditions in the south at times.

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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire
5 hours ago, blizzard81 said:

Many thanks, as always for posting these mwb. Some uncertainty as you say but it's got to be said that the clear majority have the scandi trough and ridging to our west. This would result in a marked cool down as we enter the second third of August. Those wise words of Tamara appealing to all not to take each suite as gospel are resonant in my ears. However, it is very notable that the gfs ens agree with this marked cool down so it would be reasonable to suggest that both ecm and gfs are barking up the right tree. 

The 12z gfs ens carrying on with the cool down baton as we go into the second week of August. 

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Has to be said a flip flopping suite of models usually results in an unsettled spells, how long that lasts is uncertain but from many years of model watching it would not surprise me one bit if this time next week we had low pressure makimg headway into the U.K..

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

I wouldn’t expect that at all - nothing suggesting a low pressure onslaught. Maybe lower pressure, but no washout at all. Just back to something more like average.

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Posted
  • Location: Maldon, Essex
  • Location: Maldon, Essex
4 minutes ago, blizzard81 said:

The 12z gfs ens carrying on with the cool down baton as we go into the second week of August. 

The GFS op also holding on to the hot weather in the south for longer. I think with the flipping and flopping at the moment, the ensembles aren’t the best guide at the moment.

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