model discussion Model output discussion 11th July onwards

[Mike Poole]

2 hours ago, Ed Stone said:

There's quite an intriguing look to the GFS 06Z, I think?

Not only do things look likely to be notably warm by next weekend, that Russian blocking high (should it remain) will essentially negate any chance of any deep, cold arriving from the east until New Year?

It is, of course, possible I'm talking rubbish!

    

Yes, Pete,  it is a concern I have now, more than compared to 2009, 2010.  2019 had decent winter synoptics that never delivered due to lack of cold air, until mid-December if memory serves, then it was dross for the rest of the winter.  I think there is now reasonable confidence from a number of commentators that there will be an early doors winter setup that is conducive to cold and snow, but the question is will it deliver or fall on the wrong side of marginal?  We will see.  Probably one for the winter discussion thread…

Meanwhile, I was struck by the ECM 0z clusters at the timescale beyond the current unsettled spell, T192-T240:

Clusters 2 and 4 have that high to the UK and NE (which is what I’m expecting) but there are other options too, but there is northern blocking of some sort on all of them.  Sometimes, would be good to see the NH view of the clusters, I guess.  

[johnholmes]

Turning to a closer time scale, the run up to this coming Sunday, seems a really interesting period for any amateur meteorologist and a 'pain' for any professional on duty during this period as just where the track and how deep the surface low will be Saturday through Sunday.

IF it is to deepen rapidly in that period then the jet stream has to be the reason. The 300 mb flow from GFS and ECMWF are not all that similar. For rapid deepening the flow needs to be diffluent in the vicinity of the surface feature. That simply means the flow slows down. The upper air pattern on EC and GFS is not that similar, one suggests the upper flow will be from off N America the other from a sharpening upper trough from the Greenland area. So a really interesting time.

UK Met with their latest 'possible' suggestion of how things may develop, their early morning Fax chart, see below, for 12Z Saturday shows the wave tip, already occluding 50N 8-9W. If this is so the rapid deepening, unless the Fax chart should not have been shown as occluded, is unlikely to deepen rapidly turning left in its track as it does so. Fascinating to see what todays D shift senior man is going to do with it. If only I still had contacts into the thought processes!

Fax Synoptic Charts From The UK Met Office - Neweather.tv

WWW.NETWEATHER.TV

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Latest Met Office Fax synoptic weather maps

Well worth watching in my view. Also the London marathon could be really affected depending on just what track and its depth in terms of wind strengths for the London area.

 

Edited September 29, 2021 by johnholmes

[Mike Poole]

Hell, that’s messy on the GFS 12z T84:

Pick the bones out of that!  Interesting weekend to come!

T120, tropical storm coming to our aid and causing a settling down, T120:

Edit yes T186 delivered:

Edited September 29, 2021 by Mike Poole

[Methuselah]

I think this chart was taken by the Hubble telescope:  

[mb018538]

A more amplified 12z as Sam interacts and buckles the jet stream. Still no clues as to preferred outcome at this stage!

[Methuselah]

Nae bad. Nae bad at all!    

[Mike Poole]

GEM looks nasty for the north T84:

But by T144 like the others is on the settled October march…

I think October will be largely settled and warm, and if any low pressures come in between that, then they will be exactly that, in between!  There is no driver off the Atlantic for a normal Autumn in my view.  Warm October, then what???

[Thunder and Lightning]

To be honest I don't know why everyone is wishing for settled weather after one of the most boring periods of weather in my memory!! I am very excited by the thought of any unsettled weather, and the last few days have been absolutely great. I was really excited by the prospect of a maybe stronger storm being signalled by models recently, but most have taken the foot off the gas regarding intensity. 
Hoping for a big uptrend personally by model output, but jet looks  relatively powerful and then divergent near to the UK, though deepening and associated wind speeds aren't as powerful as one might expect - though of course positioning matters a lot so needs watching. Big shift south on the latest GFS though. Wonder what will happen regarding model trends next few days. Still some quite strong winds on models for northern areas. 

Edited September 29, 2021 by Thunder and Lightning

[Eagle Eye]

On 29/09/2021 at 17:52, Mike Poole said:

GEM looks nasty for the north T84:

But by T144 like the others is on the settled October march…

I think October will be largely settled and warm, and if any low pressures come in between that, then they will be exactly that, in between!  There is no driver off the Atlantic for a normal Autumn in my view.  Warm October, then what???

Warm October

Cold November?

[mb018538]

55 minutes ago, Thunder and Lightning said:

To be honest I don't know why everyone is wishing for settled weather after one of the most boring periods of weather in my memory!! I am very excited by the thought of any unsettled weather, and the last few days have been absolutely great. I was really excited by the prospect of a maybe stronger storm being signalled by models recently, but most have taken the foot off the gas regarding intensity. 
Hoping for a big uptrend personally by model output, but jet looks  relatively powerful and then divergent near to the UK, though deepening and associated wind speeds aren't as powerful as one might expect - though of course positioning matters a lot so needs watching. Big shift south on the latest GFS though. Wonder what will happen regarding model trends next few days. Still some quite strong winds on models for northern areas. 

Because it can still be pleasant and quite mellow at this time of year? What’s the point of wishing for 14c, gale force winds and rain? Can’t exactly go out and enjoy it can you? Everyone is just stuck inside and watching it out of the window! This weekend looks pretty lively, so we can all sit inside and marvel at the strong winds and rain together, hurrah!

[Frosty.]

Having just looked at the GEFS 12z mean in the mid / longer term I think a north-south / northwest-southeast split is a good bet, perhaps even better than that with only the far north remaining unsettled and as far as the southern half / third of the u k is concerned, there are strong indications it will start to become generally settled beyond the next week or so? ️ ?  

[Thunder and Lightning]

1 hour ago, mb018538 said:

Because it can still be pleasant and quite mellow at this time of year? What’s the point of wishing for 14c, gale force winds and rain? Can’t exactly go out and enjoy it can you? Everyone is just stuck inside and watching it out of the window! This weekend looks pretty lively, so we can all sit inside and marvel at the strong winds and rain together, hurrah!

But thats just the point! The wind and rain is the best part. Because I love the weather, I naturally want to see the most exciting parts, and for me while settled weather is lovely at times, we have had boring settled weather for weeks on end, and after a change, I dont want to go back to it.

[Frosty.]

 

Compared to most of the ECMWF 12z operational (which is very unsettled / disturbed) day 10 looks best in terms of high pressure but it’s certainly on the chilly side!…  

Ex tropical storms could still play havoc with any long term predictions!   

 

Edited September 29, 2021 by jon snow

[Don]

5 hours ago, Mike Poole said:

Yes, Pete,  it is a concern I have now, more than compared to 2009, 2010.  2019 had decent winter synoptics that never delivered due to lack of cold air, until mid-December if memory serves, then it was dross for the rest of the winter.  I think there is now reasonable confidence from a number of commentators that there will be an early doors winter setup that is conducive to cold and snow, but the question is will it deliver or fall on the wrong side of marginal?  We will see.  Probably one for the winter discussion thread…

Yes, could be frustrating, particularly for us southerners at least!  No early optimism from me but one for the winter thread.  Meanwhile, some more autumnal weather to enjoy for the next few days and weekend….

Edited September 29, 2021 by Don

[johnholmes]

Looking at the latest model outputs and the Exeter newest Fax all the models seem agreed that the low is going to deepen close by the UK, see the Fax chart out this evening for 12Z Saturday, an open wave which can deepen. Previously they showed it as an occluded system which would not turn north and rapidly deepen. The jet also appears to be a NW one from the Greenland area so the deepening is occurring in the bottom of the upper trough  I would think the low itself exiting England in the NE of England as a first estimate. Windy for sure on its S/SW'ern flank and some fairly heavy rain possible on and ahead of it. Hefty showers to follow in the strong to gale (for a time) SW flow.

An interesting period up to Sunday at least.

[minus10]

Interesting ECM 12z this evening. Certainly the weather very unsettled/disturbed now. 

4 LPs move in over the 10 day period but cannot move further East before the HP ahead of Hurricane Sam. Indeed Sam enters the stage on Sunday and is loitering with intent until it makes its move on the following Friday on this run. Although this will change it shows how volatile things are at present with high levels of uncertainty: certainly not boring.....

High to the north, south and the East, so where does it go?

[Cambrian]

After the fun and games to come this weekend, prospects after day 6 seemingly tied in with the fortunes of our co-latitudinal friends in Newfoundland. 

ECM builds a decent high pressure there at 144h, holds the ex-tropical storm pretty much where it is, allowing only a modest mid-Atlantic high, maintaining a broad trough over us through to day 8 with another fairly deep low about to cross Scotland and unsettled for all.

 

 

GFS at 144h, Newfoundland under the ex-tropical storm, already modified to a more regular Atlantic low, and pumps up a generous high which migrates our way by day 8, pushing the low up towards Iceland. Relatively settled for most.

 

 

UKMO at 144h has something in between, likely supporting the north / south split idea for us down the line.

[Polar Maritime]

This morning's GFS take on Saturdays Low. Sweeps into the Channel effecting the South Coast then runs North all the way up the East Coast to Scotland..

 

[mb018538]

No real amplification on the GFS/GEM 00z runs, staying fairly flat.



UKMO has high pressure slightly more in play. 

Last night's NOAA update had the high pressure fairly close by:

[Frosty.]

More Ex tropical storm activity  having an impact on the ECMWF 0z operational further ahead, which increases the level of uncertainty?    

[mb018538]

ECM Op actually looks quite close to the NOAA chart above too. Sort of a halfway house - not completely flat, but nowhere near as amplified as some previous runs from 1-2 days ago.

Just look at this ECM rainfall chart for the next 10 days too. What a massive NW/SE split! Hills in Wales and NW England seeing eye watering totals over 200mm, so flooding definitely likely there.

[johnholmes]

Turning to this weekend and it is becoming reasomably clear on how deep and the most likely track of the low. Much as it seemed yesterday evening in terms of its track. One can see this morning's view by UK Met on the link below from its inception as a wave in the Atlantic to its position close by Shetland during Sunday.

UK Met Office Fax Charts - UKMOMSLP Analysis and Prognosis - org

WWW.WEATHERCHARTS.ORG

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UK Met Office . . Europe and North Atlantic MSLP analysis and prognosis charts

 

 

[Jamie M]

Quick comparisons for the low this weekend.

OP/Fax Runs at 72/78h:

 

Mean runs for GFS & ECM:

Ensembles for London:

It looks like a general consensus for low to end up near Shetland by Sunday, just how deep though is the question. Going to be windy though.

[Methuselah]

Well, well, well, well, well. Doesn't this morning's GFS 00Z run look eye-wateringly fantastic? No? I thought not!

    

    

   

Meanwhile, all is not revealed:

  

And, finally, the piece de resistance, the Met's 10-Day forecast:

 

Edited September 30, 2021 by Ed Stone

[mb018538]

12 minutes ago, Wimbledon88 said:

Absolutely. It's been a boring several weeks though we are at 110% rainfall for September here in London. Those 10 Day high pressure charts that keep getting posted dont seem to ever deliver,

Strange comment when a good number of days in September have been anticyclonic..




Anyway, a bit more agreement on a NW/SE split in the 8-10 day period, with the driest/most settled conditions in the SE, wetter and windier towards the NW closer to low pressure: