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Model Output Discussion - Into Autumn 2020.


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3 minutes ago, damianslaw said:

A step-change in the feel of things takes place through late September, as we descend into Autumn more fully and cross the natural divide. Through most of September there is a tug of war a pull and push between summer and autumn, by October, the release into autumn is finally kicked, any dry settled sunny weather even if temps get into the 20s has a definitively feel about it. The same step change takes place in late March.

In overall feel the most major step-change of the year takes place when the clocks go back, far more marked a change than when the clocks go forward. 

And part of that of course, is the clocks go back end October when Autumn is well in control, but with an asymmetry that baffles me, the clocks go forward end March, when most years spring has already sprung. 

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ECM indicating a return to some settled weather end of next week however a few showers & the flow becoming Northerly so the potential for some frost developing- Nice & seasonal.

Well the AO off the scale is an interesting sight !

A major change from ECMWF ahead of the winter.  

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1 minute ago, Mike Poole said:

And part of that of course, is the clocks go back end October when Autumn is well in control, but with an asymmetry that baffles me, the clocks go forward end March, when most years spring has already sprung. 

Yes if the clocks went back say end of September wouldn't have quite the same immediate effect, psychologically a change from it getting dark at 6pm to the next day going dark at 4.45, is very profound.

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14 minutes ago, damianslaw said:

A step-change in the feel of things takes place through late September, as we descend into Autumn more fully and cross the natural seasonal divide. Through most of September there is a tug of war a pull and push between summer and autumn, by October, the release into autumn is finally kicked, any dry settled sunny weather even if temps get into the 20s has a definitively different feel about it. Indeed statistically we see the most marked temp differential between two adjacent months in September and October. The same step change takes place in late March. There are therefore two step changes in the autumn season, whereas the spring season feels has perhaps just the one in late March, followed thereafter by a propelled movement through the splendour of spring, rushing headfast into summer.

In overall feel the most major step-change of the year takes place when the clocks go back, far more marked a change than when the clocks go forward. Key factor loss of daylight.

I think late August Is the first hint of autumn, with the transition between summer and proper autumn between mid August to mid September. Now moving into late Septemner, autumn is starting to become fully established.

October is fully autumn, but I feel but the time the clocks go back, it really seems like winter is taking hold, mainly due to the darkness. Even when the weather is mild late October just feels really bleak. The long dark days remain with us until late February, before things start to change towards spring again.

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GFS 18Z definitely had more than 10 pints at the pub this evening! 🍺 A very potent North-Westerly to Northerly it is showing for 27th September. Scotland, particularly during the morning, would probably be greeted with a few sleet and snow showers with the -5*C 850 hPa temperature line spilling over the country at times during that day. If this has any chance of verifying, up North, it could feel like Snowtember! (Or Sleetember!)
 

4ADF45D4-721F-4786-B6F4-ED0D3FD7B411.thumb.png.94e130c2a705231a2362645b503d5c0c.png240E1589-8ED6-422B-9B7E-617C7522A928.thumb.png.e1f7fd1689658b3c6c460ae177e30b68.pngCFFEB701-480F-43BC-B59D-0836DB7F72CC.thumb.png.fc1d50f1dea065ac09454523e2eb93ab.png96ADFD24-3CCC-4113-BFAB-E4AFA484C109.thumb.png.0d9c618f9903c24a92c9a12dd5ab7c23.pngC634711C-1DD6-45FA-A983-9A26A02F7806.thumb.png.a60c50cbda77f42917ff6e0478c52220.png7512C3ED-B29E-48C2-A382-242204007059.thumb.png.33e661b9e0e37795663cd34846aeb1bd.png

 

In the closer range, it looks like the settled and fine conditions will continue over this weekend. Though Low Pressure sitting to the South of the UK could bring along the odd shower or two at times over Southern areas. 
 

E10DE9E8-C07C-4220-9573-F36E69427776.thumb.png.f02e82c6430af8dcbae3f520de9e2c9e.png2A316919-CE0C-4758-A652-7D8192C8995F.thumb.png.92b6312806e373129f377e9589b0ac4f.png
 

Similar on Monday, though may cloud over across the far North as pressure starts to fall towards the North and North-West of the UK.

46F99C3D-D0C1-460D-8C2A-403A04F40646.thumb.png.224c68de5428fcfe631463d6de44ab59.png

 

Edited by DiagonalRedLine
Removing extra chart at bottom
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19 hours ago, cyclonic happiness said:

Well, it's a good job this morning's GFS is shoving the -4'c/-5'c 850s down as far as Oxford later this month.

Extraordinary cold northerly considering how early in the season it is, and how warm the planet is atm!!

snow3.png

Sorry for the very late post but it should be noted the GFS in particular has a cold bias as it goes further into the forecast but there is signs we may see a chilly northerly flow at some point. Whether uppers go that low ill have me doubts mind. 

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8 hours ago, Mike Poole said:

And part of that of course, is the clocks go back end October when Autumn is well in control, but with an asymmetry that baffles me, the clocks go forward end March, when most years spring has already sprung. 

I've always thought the clocks should go forward on the last weekend in February- or at the latest the first weekend in March. There really is no need to wait until the end of the month.

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It’s not so easy to find a bright side having viewed the 0z output but here goes...the GEFS 0z mean indicates some relaxation in the unsettled conditions eventually, and early October may not be to bad...but certainly next week shows a big pattern change to very unsettled and cooler although the ECM 0z doesn’t become as cold as last nights 12z whereas the GFS 0z op does look 👀 colder with a risk of snow for Scottish mountains at times, and perhaps lower levels  but it’s a complex set-up and whether or not we do get a northerly with any bite, it will become very unsettled / cyclonic with gales and rain...but also some ridging from time to time giving at least temporary respite.

D62737D2-1391-4CB7-88AE-9B5CCD170DEA.thumb.png.eab8c2123afdc5d86e45f4e06b48ffc2.pngE5255F83-0B61-482D-88B3-C23E18A77125.thumb.png.df6d29ea80022999d9c4c0a3122b3805.pngE7825645-16A6-4411-B952-919D1748F5DC.thumb.png.d27a75aadbd8c0444d359873a41b4c98.png53D21484-E875-4751-8474-F59F5E5B1CF0.thumb.png.d354bf56fbdb081ffea8a9c705b97a16.pngAC871077-0D53-4BB5-956B-12FAEE79F079.thumb.png.351fc0b4c62ec8e94180215e412bb563.png7EF6D13B-107F-43ED-B0FC-F14705C0F1F6.thumb.png.228200cbf62f6a8e2cc5556ea58cc886.png0BB2FD83-99C8-4655-A41D-8C9AE28A433D.thumb.png.d3fe1df47764130f878a400c56dc2f3e.png948BA18A-E714-4204-BB9C-2F55B3CEBEFD.thumb.png.fcfdca95204ee53b8cee0198c7b51369.png

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GFS continues to paint a rather chilly outlook for late September, with a pronounced  build of heights over Greenland, this has the effect of maintaining the presence of an increasingly cold trough. Much depends on whether the warm air advection over the NE USA seaboard/Labrador strait area is sharply defined i.e. N-S aligned, enabling heights to develop strongly in the vicinity of Greenland or not. General theme though is for a build of heights in this region, and a northerly of sorts looks the form horse. How cold it gets remains the question, but there is a chance Scotland in particular next weekend could be notably chilly, and the s word certainly may appear even down to modest levels, given there is a deep pool of cold air building to our NW.

ECM is showing less of a colder scenario but it's still a chilly one, with a flow from between north and west taking over by Wednesday and for the foreseeable, quite a plunge in temperatures is forecast.

In the short term 2-3 more very pleasant days ahead, plenty of sunshine, make the most of it everyone!

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On 18/09/2020 at 00:01, Geordiesnow said:

What I'm finding really interesting in the model output is the fact if we do get some northerly flow of some sort, the ECM especially wants to develop a massive ridge over Western Russia with what probably be record breaking heat so you think, well if Western Russia is getting record heat, there must be some cold weather over Siberia forecast given there will be a dip in the jet stream. Well absolutely not, not only we got above average temperatures, there is barely any snow cover and there is hardly anything in the forecasts so for those who think lots of snow cover over Siberia is a good sign for winter will be very disappointed with the forecasts. I for one I'm not too convinced by that link but a lack of snow cover means above average temperatures and above average uppers so coupled with lots of warm open water over the Arctic then cold air could be in short supply I feel. 

I think you'll be surprised how fast that can turn around. While it is very warm there at the moment, as soon as temps dip low enough for lying snow then synoptics could reverse the entire picture within days. Noone wants to see the arctic in such distress, but snow cover in October will arrive regardless. More interesting is the impact of all that heat energy in autumn being absorbed by the atmosphere. I dont think there has been a peer reviewed analysis of the impact on autumn synoptics of such heat loss/absorption...but it is something that gets thrown around on the forums from time to time.

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2 hours ago, sheikhy said:

Cold gfs from wednesday onwards!!temps of 10 degreees by day and 5 or just below by night!!ukmo looks the same!!had this been december or january we would be going cookoo right now😒

Aye but that's when it dosen't happen, today would actually be snowier for many, i'd have thought? but E'lys don't seem to exist between Late Nov and Late Feb

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9 minutes ago, Catacol said:

I think you'll be surprised how fast that can turn around. While it is very warm there at the moment, as soon as temps dip low enough for lying snow then synoptics could reverse the entire picture within days. Noone wants to see the arctic in such distress, but snow cover in October will arrive regardless.

My understanding is it’s the rate of snow cover advancement through October which can have a bearing on winter?  2012 has a big increase during autumn, following the record breaking low sea ice.

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7 minutes ago, Don said:

My understanding is it’s the rate of snow cover advancement through October which can have a bearing on winter?  2012 has a big increase during autumn, following the record breaking low sea ice.

It's all a bit theoretical and still unproven. One thing I look for is the classic aleutian low, euro high combination that can be a signal for a wave 2 pinch on the vortex. Whether snow cover advancing swiftly westwards is a precursor to a Euro high may be possible to argue....but of course that particular setup in October/November is too early to have a realistic impact on the heart of winter given vortex spin up in November. I'm not a convert of the snow cover index (yet) - though in general terms it seems good to me to have the siberian high strengthened as much as possible by extensive snow cover so that western europe can get a cold easterly feed and cool down. Ultimately more snow over Russia has to be better than less.....

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3 minutes ago, Catacol said:

It's all a bit theoretical and still unproven. One thing I look for is the classic aleutian low, euro high combination that can be a signal for a wave 2 pinch on the vortex. Whether snow cover advancing swiftly westwards is a precursor to a Euro high may be possible to argue....but of course that particular setup in October/November is too early to have a realistic impact on the heart of winter given vortex spin up in November. I'm not a convert of the snow cover index (yet) - though in general terms it seems good to me to have the siberian high strengthened as much as possible by extensive snow cover so that western europe can get a cold easterly feed and cool down. Ultimately more snow over Russia has to be better than less.....

To be honest out of all the LR winter forecasting tools there is, in my opinion the strongest is the PDO area in the NE pacific, a warm pool of water there has been the one constant with the long run of non-blocked winters we have had, whether the nina is a pre-cursor to the cold pdo phase i don't know, also perhaps the Atlantic, the last thing you want is a huge cold pool of water right the way from Greenland down the Eastern seaboard.

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Hi folks

The team have decided to open a thread for those wishing to discuss and post charts on the run up to Winter 2020/2021.

As we're only just in Autumn, it's a bit early to be posting Winter charts in this thread.

Of course, if cold weather is within the model output within the GFS 384 range, then it is perfectly fine to post that in here. 

For the early run up to Winter, head over to here:-

Thank you! 🙂

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8 minutes ago, Zak M said:

Here is this mornings ECM, GFS and GEM @240:

483227471_ECM1-240(2).thumb.gif.98869579a2b2871712b0ac32f1225981.gif   gfs-0-240.thumb.png.aff05be3d808f34de791ef6800c49b94.png   gem-0-240.thumb.png.5e6308d59cd0b31bf2b2bc8941d93b3b.png

All of them are showing some AH ridging, but with some cold uppers still in place from the cold plunge to the east, I would assume that it would be pretty mild (or cold in the north), with the potential for couple of frost patches in the north where temperatures drop into single figures.

Also - 1 year ago today, I made my first ever post in this thread.

I laughed looking back at that post, mainly because of the fact that I didn't know at all what that FAX chart showed and I also threw some text of a random 7 day forecast I found on the internet into it. 😂

But, I have certainly learned a lot from every post in this thread and I'm still learning a lot now, so a big thank you to everyone who has contributed to this thread. 👍

cool Zak, keep it going!

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Very impressive Zak, much more impressive than me during my first year, indeed first several years ( I was pretty rubbish to be honest..some think I still am!..😁 anyway.. I’m still learning / evolving too (late bloomer):shok:..moving swiftly on,:whistling: the Gfs 6z op does show some improvement in its later stages, at least across the south but certainly a big change coming for the second half of next week compared to what we’ve seen so far this autumn..it will certainly feel like autumn! 🍂:shok:😜 
6D499A75-39E7-4605-9C02-314EF2DF347D.thumb.png.a5bb4497b8b168ca164595b7afd81975.png6EF49F50-5CD7-431C-B96D-8A2A2CD6E07E.thumb.png.01cfb421babe1102e675d04db185837a.pngD2C5C60C-2691-43DE-A4B3-F098BB529031.thumb.png.a8ad10cacc538688b79ab3b08bbb1c17.png36308A84-E38A-452A-A872-31ED17BAECCF.thumb.png.bf3c2a778d93accaddc7925752935a00.png

 

Edited by Jon Snow
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Afternoon all!

Glorious Autumn weather up here the last few days - fog in the morning, sunshine/not a cloud to be seen in the afternoon and temperatures between 18 and 21C - perfect September weather! (Not going to last much longer unfortunately)

UKMO 144 looking very chilly!

9CD93DCD-06DD-4E18-A096-44BEF7CC5593.thumb.gif.374c81eeb19fe06a4c5e9f64c1f47092.gifED79643D-2833-43F8-BE20-E4C096103D8F.thumb.gif.d56e89c6a87468d1f428723a469ecd45.gif
 

Mountain hike planned for next Friday/Saturday...should be fun...🥶:cold-emoji:

Planning Outlook

A band of rain and strengthening wind reaching far NW Scotland on Monday, will swing erratically SE to reach England and Wales on Tuesday - though for many areas the deterioration may be late in the day (perhaps after dark). Several days of frequent rain, intermittently strong winds and lower mountain temperatures will follow as low pressure envelops Britain and then drifts east. By Thursday or Friday, particularly cold for late September, with snow lying on many Scottish summits and perhaps on some higher tops elsewhere.

https://mwis.org.uk

Great time of the year for a bit of weather variety!

All the best everyone - have a great weekend!

Edited by Mr Frost
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The 12z Ecm does appear to have downgraded the unsettled Wed-Fri period somewhat although still distinctly autumnal compared to what we’ve enjoyed these past couple of weeks. And if this 168 hr chart is anything to go by I wouldn’t be quite so sure that these North Atlantic lows will suppress the now familiar Azores ridging to any great extent.

D3262B23-845F-4352-BFF5-ED17C0D3C652.jpeg

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The ECM 12z operational looks pretty unsettled too me following a settled start, there is a bit of temporary respite / ridging for a time towards the end of next week but it soon becomes unsettled again, it doesn’t look terribly cold though but certainly an autumnal feel.

54C9345A-FA92-44E7-8D18-D9F4CA426E33.thumb.png.b85f3939ee5e54b4b81cee76772b018e.pngABE1EA90-3895-4087-9CFE-FC9C3A94FDC8.thumb.png.ca635aea6218a5f8b18706d8f0e0272b.png838CED8C-F929-42F1-A4FE-E859E2E189CA.thumb.png.f7cd11221155654d3deed5b0187cb607.pngCBC95CD1-02EA-4841-8AEF-85A9EDC944F3.thumb.png.edf30f5a5ce8a3af9b06c4bac1f47ef4.png6589729F-5EF5-476A-8714-21436127EFF5.thumb.png.bf354c1254366b705fb4956d2ceca89e.png214484C5-5E7C-41AB-B9BF-8589F69EEA57.thumb.png.a9fb5f60136988d1893324010127d176.png8969210B-D5E1-4673-A213-9EDE4A75D947.thumb.png.dbe9e50c06253836ea7422a11152475d.png

 

Edited by Jon Snow
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16 minutes ago, Newberryone said:

The 12z Ecm does appear to have downgraded the unsettled Wed-Fri period somewhat although still distinctly autumnal compared to what we’ve enjoyed these past couple of weeks. And if this 168 hr chart is anything to go by I wouldn’t be quite so sure that these North Atlantic lows will suppress the now familiar Azores ridging to any great extent.

D3262B23-845F-4352-BFF5-ED17C0D3C652.jpeg

Unfortunately, there's not much sign of anything settled in the FI period on the ECM 12Z.

The exact timing and trajectory of the ex-Hurricane Teddy remains pivotal. The current path has it making a brief landfall in Nova Scotia before curving back NE but it's not clear if it will move to the west of Greenland which would cause heights to rise over eastern Greenland and bring the trough down over western Europe or whether it would phase into LP moving over southern Greenland thus giving the jet a brief kick. 

I've put up the T+240 Northern Hemispohere chart to show the large HP over NW Russia which is forcing thr Atlantic trough to align negatively into north-west Europe. The set up is a classic NW-SE alignment leaving the British Isles on the colder side of the street.

ECH1-240.GIF?19-0

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