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Model output discussion - here comes the beast!


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Please only post model discussion in this thread 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

We also have a special post SSW cold spell discussion open here:
https://www.netweather.tv/forum/topic/89358-ssw-related-cold-spell-will-it-wont-it/

Thank you!

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UKMO 12z has the -12 line in the SE corner at t144 with the -8 line around the Scottish borders

UW144-7.thumb.GIF.3fc459be364443d1b797537793508824.GIF

00z had the entire country under the -8's with Lincolnshire south under -12's?

UW144-7444.thumb.GIF.8a2ec02bb480aae920fdd4adff38a086.GIF

Obviously, the time frame is different but that is definitely a shift south for the coldest air - not that the UK would be all that warm anyway

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Early guidance forewarning of next weeks weather was issued earlier on, and this has been further enhanced with extended outlooks in bulletins. AFAIK (comms not being my area) public agencies and majo

Come on those looking for the breadown before the major cold and snow has begun You will be very lucky if that is the correct word to see this in ANY winter in the rest of your lives I would sugg

Microscale detail absorbing an awful lot of attention on here, when in reality it is a waste of emotion. The macroscale pattern is now fixed - it will not change significantly now for the start of nex

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2 minutes ago, Mucka said:

I'm not thrilled by the UKMO, ICON and this mornings ECM all going for a less exciting evolution but I still think it is a trend that could be reversed, or at least revised back toward something more favourable for the whole country.

Certainly not something we want to see continued and progressed upon tomorrow but @carinthian's report of a quicker progression to cold sounds hopeful as that would likely have the initial ridge and high further North 

Indeed, we have seen the trends reversed before and we don't have access to the tools that the Meto do.

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GFS OP very different from ECM, ICON and UKMO. Big northwards correction with goes against the other models in which the high moved slighly southwards. Wait for the mean as OP could be an outlier before coming to a judgement. Southwards correction looks a trend and I think most the cold air will end in France and we'll end up with HP with a dry easterly. Nothing too cold or drastic.

Edited by WalsallWeather123
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18 minutes ago, Southender said:

Wow, just wow. There are some seriously inaccurate posts flying around at the moment. Please, if you do not understand how to read the models correctly either ask a question or read up on things, there is some excellent learning material on here and across the web. This is a place to learn, but at the same time posting wholly inaccurate info just inflames a situation further.

Anyhooooo, lovely GFS run eh?

 We do not want a shortwave forming in the north sea . Firstly It prevents the cold air advection lifts heights and secondly will mix out the colder uppers and although it fine for snow on this run ,the seasoned campaigners on here have seen this before. Clean and aggressive this run or the last are not.

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Many British residents were left fuming  as forecasters forecast rain  "its just not on"   Mr Jones 45 from wales said  a he was  forced to ski  to top up his electric metre.

gfs-2-210.png

gfs-2-216.png

gfs-2-222.png

Edited by weirpig
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Is it schadenfreude or deep rooted pessimism that's the driving force behind some of the posts in here of late? I've been a member of this forum for 13 years but at times like this it's almost unbearable trying to find a measured viewpoint to the models.

A couple of people have already stated that they are dodging the forum for the foreseeable and I'm thinking of joining them.

As ever the models beyond +144 are not reliable, especially in finer detail. Up until +144 they are all in broad agreement that we are going to get a potent cold blast with snow. Can't we all just appreciate that?

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With the exception of the GFS, all other models have shifted south - some slightly, some more so.  ARPERGE (shown below) probably the most southward.  I believe its the shortwave to the north of Iceland that is putting the southward pressure on the block - but I could be wrong?.

arpegeeur2-0-114.png?12

We await the ECM with baited breath as this was was the first model to call out the southward shift.

Edited by mulzy
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1 minute ago, Summer Sun said:

UKMO 12z has the -12 line in the SE corner at t144 with the -8 line around the Scottish borders

UW144-7.thumb.GIF.3fc459be364443d1b797537793508824.GIF

00z had the entire country under the -8's with Lincolnshire south under -12's?

UW144-7444.thumb.GIF.8a2ec02bb480aae920fdd4adff38a086.GIF

Obviously, the time frame is different but that is definitely a shift south for the coldest air - not that the UK would be all that warm anyway

Shifting south seems to be the trend, I've noticed the last few days that the ARPEGE has modelled the high to sit off the north west coast of Ireland. Giving us more of a dry cold rather than very cold maybe snow. Hopefully ECM keeps the high further north over Iceland/Greenland. How do you reckon this spell is going to unfold? 

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What a strange place this has become.......

The ECM 12z operational shows virtually the whole of the UK under at least -5 to -10 air, briefly flirting with -15, from T120 right out to T240. The slightly 'messy' picture in fact means more potential for smaller scale disturbances and troughs, so more likelihood of snow, and yet people are not happy ??? Honestly, how much would most people have given for charts like these at just about any point over the last 6 or 7 years ???:

ECMOPEU00_120_2.thumb.png.0621bb384fbd97c936765d04de3c7d98.png

ECMOPEU00_144_2.thumb.png.2da75e6a8fa09b5ead08a4f9cae8d45b.png

ECMOPEU00_168_2.thumb.png.14a39826c13ddce0030b2a64fcce2caf.png

ECMOPEU00_240_2.thumb.png.afcd021e5a2d174d0093b5e3ad5ab71c.png

ECMOPEU00_216_2.thumb.png.91beb37fdb8c0ba4c8799abfc1d44ffc.png

ECMOPEU00_192_2.thumb.png.516227c43ddb8b3d8b40b8ad56b1f26a.png

It's beyond bizarre !

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3 minutes ago, Staffordshire said:

ECM 12z on the 19th and 20th vs the 0z for 28th 01:00... yes I am sure.

 

GFS 12z much nicer though.

19th ECM 12zECM1-216.GIF?00EDM1-216.GIF?00
20th ECM 12zECM1-192.GIF?00EDM1-192.GIF?00
21st ECM 0zECM1-168.GIF?00EDM1-168.GIF?00

So the high moved west from the 19th to the 20th, then the high moves back west from the 20th to the 21st......

The upper high actually migrates (north over those three runs, the 21st looks more like the 19th.

there is no trend, so to predict anything from that is well..... a folly. (or a troll)

Added the means too......

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7 minutes ago, Mucka said:

I'm not thrilled by the UKMO, ICON and this mornings ECM all going for a less exciting evolution but I still think it is a trend that could be reversed, or at least revised back toward something more favourable for the whole country.

Certainly not something we want to see continued and progressed upon tomorrow but @carinthian's report of a quicker progression to cold sounds hopeful as that would likely have the initial ridge and high further North 

Indeed, and you make an excellent point there. The Met outlook and @carinthian's report show us that the professionals have access to data us poor schlubs never see. This then gets combined with their own human expertise, which is often a vital element of making forecasts in unusual situations such as we see before us. It should make us take any commenting on the publicly available data with a little pinch of salt!

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Just now, kev238 said:

I don't think anyone can really forecast anything from the models with certainty ( beyond Sunday)  apart from it will turn much colder and it shall feel bitter in the wind. There might be snow almost anywhere; equally there might not be.

yep as you say very cold from Sunday but in the mid-term lots of options

big differences at just 96hr in where the models take the vortex/parts of it all 4 12z runs (icon/gfs/Gem/UKMO) deal with it very different manner which effects how far north block goes and whether we keep easterly feed or end up with northerly.

means may give an idea but I think we may be waiting till Saturday to get cross model agreement for middle of next week.

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A couple of points worth making:

1) The instabilities within the cold pool are going to be very difficult to forecast at this range and because the severity of the cold pool isn't comething we normally experience in the British isles, it may be difficult for us as well. Analogous to troughs within an unstable Arctic flow I would imagine.

2) It's worth repeating if you want a protracted cold spell you don't want to see a lot of snow early. With the cold pool promoting instability and lowering heights, yes, you get the snow but it opens the door to the south and west for a return of milder air as shown on GFS at T+240:

gfs-1-240.png?12

Snow falls on Tuesday, melts by Saturday.

A more sustainable cold evolution needs the HP to be stronger to the north and north west and that may mean less initial excitement for snow fans but the likelihood of 7-10 days of severe cold weather rather than 2-3 which is on offer with the so-called "better" GFS.

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12z Arpege further south with the coldest, most unstable airmass too;

arpegenh-0-114.thumb.png.5b0401db7ca78d797fd072355928243b.png 

arpegenh-1-114.thumb.png.244c26b779f190065bf1ff8ee9d77e12.png

So, UKMO 12z & 12z Arpege look like going down the cold but less snowy route to start next week.

Worth noting however, a colder than normal airmass is likely to meander around the UK for a good deal of time, so the chance of snowfall, at varying times across varying parts of the UK, is much greater than normal for this time of year.

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1 minute ago, mulzy said:

With the exception of the GFS, all other models have shifted south - some slightly, some more so.  ARPERGE (shown below) probably the most southward.  I believe its the shortwave to the north of Iceland that is putting the southward pressure on the block - but I could be wrong?.

arpegeeur2-0-114.png?12

We await the ECM with baited breath as this was was the first model to call out the southward shift.

That’s the shortwave I’ve been droning on about since yesterday .

Until that’s resolved then I’d  be dubious of the outputs in relation to where the block sets up.

They all handle shortwave energy there differently , which impacts how far north the high is and the flow into the UK.

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58 minutes ago, Summer Sun said:

That pool of slightly less cold air to the north of Scotland is a bit further south compared to 00z doesn't make any difference to the UK

icon-1-141.thumb.png.fe78fc4d1ab25f6e44f404c34abae4ba.pngicon-1-153.thumb.png.6d3196e998aae602ef6aadaadb526d08.png

Seems to make a difference to the 850 values in the south the coldest are pushed into France on the latter.

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16 minutes ago, Mucka said:

I really would ignore this GFS run. It will be different tonight because the chances of that trough developing in the same way and stalling over Scotland are less than 1% IMO

Aw, let those of us in NE Scotland, who haven't seen much snow this winter, dream for another 6 hours. 

240-780UK.GIF?21-12

Yep, not all of Scotland has had a "decent winter already". Repeated NW flows are just as poor for some this far north as they are further south. 

I agree though, it'll be nowt but a dream,  and will inevitably change on the next run. The massive difference between the 12Z GFS and UKMO at t144 ably illustrates this. 

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Well the GFS unexpectedly ends up further north then the previous run, the UKMO in itself is still good but we want the cold shot of air right over the UK. Pretty nervous just because we are at the exact same point as we were in February 2012 before the southward corrections began.

To see GFS and UKMO be further north and south then previous runs makes me feel a scenario in the middle is still plausible. It's just when you look at past close calls when these kind of cold pools have missed us, its becuse the cold went to France. Hence southwards corrections make me feel edgy.

Come on ECM and settle our nerves haha.

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There is no denying the outputs are not as good in the last 36-48 hrs. There are no more comparisons to 87 or 91, as this at best will not top. Many on here are correct to be cautious of any more southward corrections as we have very little margins left, I think it is wrong for these people to be shot down in flames for suggesting this could happen. I just hope for this forums sake we see a correction northward in the next few days.

 

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