Model Output Discussion - mid Autumn

[IcySpicy]

This high-latitude blocking is so, so unnecessary right now, bringing near freezing temperatures to my part of Europe. Would be nice setup in January, but not now.

[northwestsnow]

EC looks very wet this evening...

 

[Jacob]

53 minutes ago, IcySpicy said:

This high-latitude blocking is so, so unnecessary right now, bringing near freezing temperatures to my part of Europe. Would be nice setup in January, but not now.

That’s exactly what I’m thinking

[WYorksWeather]

GFS vs ECM 12z runs. Both models are close to their ensemble means. Temperatures broadly average.

   

At T+72, both GFS and ECM show low pressure out to our west, a little weaker on GFS than ECM.

 

At T+120, deep low pressure piles in from the west. This time it's a little stronger on GFS than ECM, but broadly a very wet pattern on both.

 

At T+168, those low pressure systems are right over the UK. We could well be looking at two named storms in as many weeks if something like this comes off. Note that yet more low pressure is away to our west, and an ex-tropical feature visible on the GFS.

 

At T+240, yet another deep low pressure system absorbs the ex-tropical system, and then piles in on the GFS. ECM lacks the tropical system, and my guess is that the low therefore has a bit less energy, as it stalls just to our west, with some potential for eastern areas to get something a little more settled, though likely still showery at times. More of a traditional NW to SE split.

 

Finally, the GFS extended eventually settles things down right at the very end. You'd think this would be quite a mild pattern, but the surface flow is north-easterly and so it's probably cool and settled. Long way off though.

In summary, I think if you're wanting any sustained settled weather for the rest of October you're out of luck. It's a case of watching and waiting to see if we're able to eventually get a solution closer to what the GFS extended is showing.

Rainfall accumulations on the GFS and ECM out to T+240 are still very high, and this is coming in addition of course to all the rain that has already fallen over the last 24 hours. On balance ECM probably slightly less wet than GFS, but pretty unsettled all round.

 

[ANYWEATHER]

Unfortunately the trend for another ten days of wet weather coming up for the UK , looking at the Ecms ten day precip chart. Hopefully though weather system's going through quicker rather than getting stuck over the uk like they have been....?.The sunny warm weather of early October seems a million years ago, at this rate it's going to be a long winter

 

 

 

 

[Summer8906]

1 hour ago, ANYWEATHER said:

Unfortunately the trend for another ten days of wet weather coming up for the UK , looking at the Ecms ten day precip chart. Hopefully though weather system's going through quicker rather than getting stuck over the uk like they have been....?.The sunny warm weather of early October seems a million years ago, at this rate it's going to be a long winter

 

 

 

 

Not just the UK but it's remarkable how wet large swathes of the continent are forecast to be, particularly France, southern Germany, Italy, the Alpine region and the western Balkans.

Edited October 21, 2023 by Summer8906

[minus10]

Yes a pretty unsettled outlook with more rain and wind...

gfes 0z looking pretty wet here at times with temps at or just below average..

..0z pressure ens showing more of a shift to this unsettled theme i think when compared with yesterdays 12z..

..certainly the op has dropped the previous theme of more of a rise in pressure as we go into November ...seems these unsettled patterns once in go on repeating ...only positive i think is that areas of rain will be moving through quicker than has been seen recently...still little comfort for those flooded areas accross the country....

[ANYWEATHER]

36 minutes ago, Summer8906 said:

Not just the UK but it's remarkable how wet large swathes of the continent are forecast to be, particularly France, southern Germany, Italy, the Alpine region and the western Balkans.

Yes even Spain and Portugal are getting deluged. 

[Rain All Night]

How's the signal for an improvement at the beginning of November doing? It looks a little weaker than yesterday, though I remain hopeful. Here are some ensemble mean charts all showing the same point in time, 00hrs on Thu Nov 02 (which is now day 12), from each of the last three runs of the ECM and GEM ensembles:

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You can see that the ECM in particular may have been getting a bit carried away yesterday. Its cluster analysis this morning, showing the first few days of November, produced two clusters, the smaller of which is the cluster of blocked outcomes:

For comparison, here is the weekly mean height chart for the first week of November from the EC46 run initialised yesterday morning, when the main ECM ensemble was feeling more optimistic:

The interest of the GFS ensemble in an improvement, while less than that of the ECM, had been growing, but I can see that as of its 18z run last night, that interest has fallen away again significantly.

Edited October 21, 2023 by RainAllNight

[Rain All Night]

The ECMWF seems to have again expanded its repertoire of machine learning models to include one of its very own, which it is calling the "AIFS" (the formal name of the regular ECM model being the "IFS"). We can now view outputs from this model alongside those of the other machine learning models we have already seen from Nvidia, Google and Huawei. My understanding is that the reason the ECMWF is able to run so many of these models at once is that they require vastly less computing resource to run than traditional models.

https://charts.ecmwf.int/chart-set/Latest forecast?base_time=202310210000&productNames=medium-mslp-wind200&productNames=aifs_medium-mslp-wind200&productNames=fourcast_medium-mslp-wind200&productNames=graphcast_medium-mslp-wind200&productNames=pangu_medium-mslp-wind200&projection=opencharts_north_atlantic&valid_time=202310310000

You can see that at 0z this morning, all were showing broadly similar outcomes for the UK for Hallowe'en in ten days' time.

For comparison, a more familiar Z500+MSLP view of the regular ECM model output shown top left above:

As a reminder, the way that these machine learning models differ from traditional atmospheric models is that instead of trying to "fast forward" the state of the atmosphere by using (approximations of) the laws of physics, they use re-forecasts of historical weather going back decades (which are produced using the regular ECM model, meaning that that model is still needed) to "learn" how the atmosphere works, and then use the patterns they have "learned" to try to "fast forward" the current state of the atmosphere.

Edited October 21, 2023 by RainAllNight

[damianslaw]

This thread has been notably quiet in recent days, perhaps no surprise, given the models are offering more of the current conditions right out to the end of the month with exception of immediate outlook. 

Short term, a 48hr window of dry weather, which many will be grateful for I suspect. Average temps.

Rainfall for everyone Tuesday onwards but hard to pinpoint where will see the most. 

Temps holding near average.

Southerly tracking jet, with low heights and trough stuck limpet over the UK.

No obvious clear signal how we will emerge out of this very unsettled spell, as yet... good to hear views of prospects for November.

[swfc]

Evening. Ten days or so ago the nhp looked full of heights to the nne. The switch as been flicked and the pv has woken. Not a great week ten days ie rain amounts ete but not long fetch sw winds. Hopefully November will bring a change ie meto longrange

[northwestsnow]

All looks very mobile for a while.

Hence I'm not posting much..

[Ross90]

GFS looks even worse in FI, big storm over the UK on the 2nd with 80mph gusts. Hopefully it's gone on the next run.

[damianslaw]

16 minutes ago, swfc said:

Evening. Ten days or so ago the nhp looked full of heights to the nne. The switch as been flicked and the pv has woken. Not a great week ten days ie rain amounts ete but not long fetch sw winds. Hopefully November will bring a change ie meto longrange

The heights are there still, but fairly weak, and more to the NW in time, the trough is deep though, sign it may shift east eventually, but there appears to be no signal for any block to stop further low pressure squeezing in from the west at the weak spot.. low pressure might be forced on a more NW- SE alignment as we enter November thanks to heights holding to the NW.. it does look a very wet prospect and non too mild either. 

[ANYWEATHER]

By the end of this upcoming week gfs paints us all in a broad swathe of an upper level trough ,but by then the signal for any blocking has been removed by then ,so even though there will be plenty of rain bearing fronts moving across the nation, the rain will be pushed along quickly by fairly brisk winds . Pretty standard conditions for late October early November and enough injections of PM air at times to make it feel cold and seasonal and these conditions affecting a lot of southern Europe as the jet stream tracks a little way south of the Uk, still not good news for the flood hit areas but at least a respite to come later next week although some slow moving rain bands to come again as we move into the first part of this coming week.......

[Summer8906]

24 minutes ago, ANYWEATHER said:

By the end of this upcoming week gfs paints us all in a broad swathe of an upper level trough ,but by then the signal for any blocking has been removed by then ,so even though there will be plenty of rain bearing fronts moving across the nation, the rain will be pushed along quickly by fairly brisk winds . Pretty standard conditions for late October early November and enough injections of PM air at times to make it feel cold and seasonal and these conditions affecting a lot of southern Europe as the jet stream tracks a little way south of the Uk, still not good news for the flood hit areas but at least a respite to come later next week although some slow moving rain bands to come again as we move into the first part of this coming week.......

Mind you if that Fri 27th chart (about as bad a chart as you can get!) is a "respite later next week", I hate to think what happens when the respite ends!

It's one thing the fronts moving through quickly, but with pressure so extremely low, I'd expect dull weather with frequent downpours even between the fronts (bit like Thursday just gone in the south) - so really no respite at all.

(Or do you mean a respite later the following week? Pressure is less extremely low by then on the GFS 12z which suggests it will be less wet, albeit still rather damp and drab; basically it brings in mild, dull SWlies but pressure rises somewhat in the south).

 

Edited October 21, 2023 by Summer8906

[Summer8906]

51 minutes ago, damianslaw said:

The heights are there still, but fairly weak, and more to the NW in time, the trough is deep though, sign it may shift east eventually, but there appears to be no signal for any block to stop further low pressure squeezing in from the west at the weak spot.. low pressure might be forced on a more NW- SE alignment as we enter November thanks to heights holding to the NW.. it does look a very wet prospect and non too mild either. 

At least a NW-SE track might dramatically improve sunshine levels - Nov 1996 is the first thing that springs to mind for NW-SE lows at that time of year.

Edited October 21, 2023 by Summer8906

[damianslaw]

Hazard a guess but I suspect if you averaged out pressure anomalies for last week of Oct, it would show a mirror image of what is in prospect, i.e. low deep heights over the UK. Settled weather in late October always seems hard to come by. 

Edited October 21, 2023 by damianslaw

[Summer8906]

3 minutes ago, damianslaw said:

Hazard a guess but I suspect if you averaged out pressure anomalies for last week of Oct, it would show a mirror image of what is in prospect, i.e. low deep heights over the UK. Settled weather in late October always seems hard to come by. 

Even still, this year pressure seems forecast to be particularly low. While I agree that late Oct is almost always poor to some extent, it seems to be spectacularly so this year - I doubt mean pressure in late Oct over southern England is below 1000mb.

[Nick2373]

12z keeps the temperature around the average mark for the next week, showers  seem to be the outlook. After that it’s just a mess perhaps some sort of change to something colder. 

[Newberryone]

The 12z Ecm does perhaps present a ray of hope with regards to something drier developing for Halloween and probably going forward from that point too as heights build strongly over Central Europe having the effect of diverting Atlantic weather systems well away to the northwest. We can but hope.

[Kirkcaldy Weather]

So looking at what's happening in the next 10 days approx first the transition to the negative PNA which will factor greatly into the overall synoptics

Taking the setup from July 1st - July 15th

Why am I using these dates to compare with the pattern through late October 

The strength of this negative PNA matches nice with the 1st part of July, obviously some teleconnections will be different as was in July however taking the standard negative PNA setup 

️ Blocking High to our East Northeast

️ Increased high pushes Northeast through the east---->Northeast US

️ Alaskan High strengthens with the East Asian trough associated Jet to its south 

️ West coast cut off low and troughing 

On 17/10/2023 at 17:23, Kirkcaldy Weather said:

Indeed. Fast forwarding to Oct 24th we really see this switching from positive to negative phases as the Alaska trough flips to an elongating high as discussed previously this will connect with our Scandinavia / Northeast blocking and the opposites also occur as the United States west coast high pressure shifting to a trough and finally a bit of respite for the North East US toward the maritimes with the trough switches into a building high which carries the exact orientation as the previous trough from the Gulf of Mexico

Our trough will also connect energetically to the west coast trough at least briefly 

 

This switches the recent west coastal heat into a cold plunge with the heat transferred East 

I've enjoyed researching the PNA further extending more information than the bits I knew already and having found multiple papers there's a clear connection with the PNA and upstream blocks either Scandi Greenland or a mix of both which stems from Rossby Wave Breaking in most scenarios as we are and have witnessed lately 

With the stalling MJO still sat between phase 8 and 1 we are already seeing how this sets the next evolution into reality

First the PNA switching 

As the outlook chart shows by Halloween the PNA rises as Current signals have a huge cyclonic and upper level trough signal moving East southeast across Canada 

This is likely linking with our configuration into November with further energies from it feeding into further Atlantic RWBs with renewed unsettled and most probable STORMY patterns prevailing 

  

There is however an opportunity which could come if a RWB causes a cut off low to go south whilst the blocking to the Northeast connects across Greenland and the Alaskan high 

We will see the Russia and extension across Siberian high begin to develop too and an eye catcher from the EC which ramps up the Strat warming as that gets going 

As this cyclonic trough over Canada develops through Halloween we are seeing the initial warming which I had discussed as a genuine possibility  

Full house with the stretching first 

A number of output attempt an October Split which is madness

Amounts increase at 50hpa

[damianslaw]

Thanks for post above, after the deluges of late and continued unsettled outlook, I think many will hope for the cut off low to SW scenario with heights to the north and east fending off the atlantic. As said if we were deeper into winter, I'd expect the cold dense air to hold its ground, alas its the time of year when 9 times out of 10 the atlantic has its way. I always expect atlantic wet weather late Oct and into November. A grin and bear it period. 

Edited October 21, 2023 by damianslaw

[WYorksWeather]

Bit later than usual but I'll do the 18z GFS vs 12z ECM. 12z GFS ensemble is shown below for reference, 18z may be different.

 Overall, the ensemble means are quite close to the long-term mean.

 

At T+66/72, GFS slides a slow moving low along the east coast of central/northern England and Scotland, which looks very bad for areas already affected by flooding. ECM moves it through a bit faster from west to east, which is probably the best of the two options from a flood risk perspective.

  

At T+114/120, GFS and ECM both have deep low pressure out in the Atlantic. GFS brings it in closer, ECM a little further out to sea.

 

At T+162/168, GFS swings the low in even closer. ECM briefly flirts with this idea but then sends the deepest area of the low back out west. From a pure flood risk perspective again I think we need to be rooting for ECM here.

 

By T+240, finally a bit of a light at the end of the tunnel. GFS goes for a NW/SE split so at least some of us will get some drier weather, and ECM goes further by building up a ridge that gets at least to central areas.

 

The GFS extended continues in a similar vein to the position at T+240, bit of a NW/SE split, settled interludes in between showery bursts. Pretty mild.