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Model Output Discussion - cold spell to end Autumn

Paul

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/

Thank you!

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2 minutes ago, nick sussex said:

Before everyone starts dusting the sledge off I'd urge a lowering of expectations given not just the timeframe but the disagreements between the big 3.

Even if all 3 agreed at this range the low track and highest risk area will likely change between outputs. These set ups are notoriously difficult to forecast with much accuracy 5 days out.

 

 

 

Hi I'm new to this but would it be better to see if the low/northerly still shows after the weekend say 12z sunday/00z Monday to have some confidence in the output. We have all been here before and not all models agree. I love the snow and cold but it scares me to get too excited so I lower my expectations so I would wait while after the weekend what's your take on this nick regards stefan .

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Can't believe we are seeing such differences just 5 days out, would take GFS with a massive pinch of salt while MetO and ECM not on board

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13 minutes ago, weathermadbarnsleylad said:

Hi I'm new to this but would it be better to see if the low/northerly still shows after the weekend say 12z sunday/00z Monday to have some confidence in the output. We have all been here before and not all models agree. I love the snow and cold but it scares me to get too excited so I lower my expectations so I would wait while after the weekend what's your take on this nick regards stefan .

Hi and welcome.

I think the northerly isn't so much the issue in terms of verifying, the longevity of that is uncertain but in terms of appearing that's more likely.

The low tracking east and engaging colder air is really only showing on the GFS, the ECM and UKMO take longer to advect the cold south, it might still be possible to see some backedge snow with those but they bring the coldest air after the low has cleared through.

Lets say the big 3 all agree in terms of the GFS trend then yes its best to wait till T72hrs to get an idea of the track area of the low, the margin for error in terms of snow line is higher then.

The key is to get sufficient cold south to undercut the precip.

 

 

 

Edited by nick sussex
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26 minutes ago, nick sussex said:

Before everyone starts dusting the sledge off I'd urge a lowering of expectations given not just the timeframe but the disagreements between the big 3.

Even if all 3 agreed at this range the low track and highest risk area will likely change between outputs. These set ups are notoriously difficult to forecast with much accuracy 5 days out.

 

 

 

Nick 

I do agree.....

It will have to be a perfect combination of timing to get the low at exactly the same time that the cold is streaming down from the North.

A one In a thousand chance I would guess. 

However the GFS op has shown  and returned tothis scenario 4 or 5 times now over the last 4 days. It keeps coming back to it. It must be picking up quite a strong signal that something will be occurring.

The fact is that we have not got cross model agreement on it yet.

But the other models do seem gradually to be coming into line.   ??? 

It will make a lot of people on here very happy. It will probably shut down the country until after the weekend.:bomb:

MIA 

Edit just seen Rollo's post above and I echo those sentiments entirely.

It is looking more and more 62'ish.

Edited by Midlands Ice Age
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8 minutes ago, steveinsussex said:

we get huge downgrades 24 hours out at times so fully expecting big changes over next few days

dont worry steve, we'll get some snow here in sussex. i cant wait to get out there with the kids, building a snow-ant, all kitted out in my snow shoes.

havaianas-flip-flops-havaianas-kids-top-mix-flip-flops-pool-green.thumb.jpg.e646cb93e0aabe07a98828697b3bc2b3.jpg

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1 minute ago, weathermadbarnsleylad said:

Hi I'm new to this but would it be better to see if the low/northerly still shows after the weekend say 12z sunday/00z Monday to have some confidence in the output. We have all been here before and not all models agree. I love the snow and cold but it scares me to get too excited so I lower my expectations so I would wait while after the weekend what's your take on this nick regards stefan .

Totally agree ,i will be waiting a while yet ,5/6 days in meteorological time is time for it all to go pear shape .The low could whistle into France ,no real cold air to bring in to the mix ,it could even dive south east ,and other synoptic outcomes could happen ,. I am very excited myself but many many years of studying weather and looking for good snowy setups as taught me to be a little patient and get to the three day range and a back up from the met office ,But very interesting watching coming up ,cheers gang:cold::cold:

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1 minute ago, bobbydog said:

dont worry steve, we'll get some snow here in sussex. i cant wait to get out there with the kids, building a snow-ant, all kitted out in my snow shoes.

havaianas-flip-flops-havaianas-kids-top-mix-flip-flops-pool-green.thumb.jpg.e646cb93e0aabe07a98828697b3bc2b3.jpg

Bugger , flip flopping models :nonono:

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2 minutes ago, nick sussex said:

Hi and welcome.

I think the northerly isn't so much the issue in terms of verifying, the longevity of that is uncertain but in terms of appearing that's more likely.

The low tracking east and engaging colder air is really only showing on the GFS, the ECM and UKMO take longer to advect the cold south, it might still be possible to see some backedge snow with those but they bring the coldest air after the low has cleared through:

Lets say the big 3 all agree in terms of the GFS trend then yes its best to wait till T72hrs to get an idea of the track area of the low, the margin for error in terms of snow line is higher then.

The key is to get sufficient cold south to undercut the precip.

 

 

 

Ok I see thanks for taking the time to reply, let's hope ecmf and ukmo jump on board with GFS .

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3 minutes ago, legritter said:

Totally agree ,i will be waiting a while yet ,5/6 days in meteorological time is time for it all to go pear shape .The low could whistle into France ,no real cold air to bring in to the mix ,it could even dive south east ,and other synoptic outcomes could happen ,. I am very excited myself but many many years of studying weather and looking for good snowy setups as taught me to be a little patient and get to the three day range and a back up from the met office ,But very interesting watching coming up ,cheers gang:cold::cold:

Yes very exciting ha ha .

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I've gotta say the GFS ensembles are the best I've seen all season for sure. Lots of intra-model agreement as well as inter-model agreement. First time this season there's a very definite drop in temps with less scatter in the GEFS, with some bringing 850 temps below -10 for my area in the North East. Interesting week ahead. 

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2 minutes ago, Midlands Ice Age said:

Nick

I do agree.....

It will have to be a perfect combination of timing to get the low at exactly the same time that the cold is streaming down from the North.

A one In a thousand chance I would guess.

However the GFS op has shown  and returned tothis scenario 4 or 5 times now over the last 4 days. It keeps coming back to it. It must be picking up quite a strong signal that something will be occurring.

The fact is that we have not got cross model agreement on it yet.

But the other models do seem gradually to be coming into line.   ???

It will make a lot of people on here very happy. It will probably shut down the country until after the weekend.:bomb:

MIA

I'd love to see the GFS verify as it would make a lot of snow lovers here very happy and after some poor winters its certainly deserved.

I think however the low will probably be less deep if it does verify. In terms of the others well the ECM has hardly covered itself in glory over recent days. The UKMO has been okay but theres nothing to suggest that the GFS has to be wrong.

We'll see in the morning, fingers crossed the Euros come on board.

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We should get no more excited than we did about the output last night at this range.  It is model porn, for sure, but how often have we seen model porn for it not to happen?

November 2009 was something else - from the second I saw that modelling over a week out, I knew (and I am sure others did) that that was going to be something exceptional.

This requires very exact behaviour of an undeveloped Atlantic low.  Sure it might happen.  It should be watched for.  But it is highly unlikely even on current modelling - I am not even certain that the cold will arrive for most of us.

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All the models are saying more or less a similar outcome if albeit details wise still a lot of variability. It will be interesting how this plays out though because this low will bring quite a bit of mild air and PPN so having some cold air filter in ahead of it somewhat will help. A shallow feature will definitely boost any snow potential but I would side on caution and suggest most places will likely too see rain with perhaps a bit of back edge snow but at least another Northerly shot is looking a bit more likely and coming closer to the reliable timeframe unlike some of yesterday runs.

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While we wait for the 00z runs it might be worth bearing in mind Exeter have updated their outlook a short time ago and again there is very little mention of snow next week...mainly wind and rain followed by wintry showers and then a wet weekend....

In other words they are having absolutely nothing to do with recent GFS ops or for that matter the GEFS.

 

Edited by northwestsnow
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20 minutes ago, northwestsnow said:

While we wait for the 00z runs it might be worth bearing in mind Exeter have updated their outlook a short time ago and again there is very little mention of snow next week...mainly wind and rain followed by wintry showers and then a wet weekend....

In other words they are having absolutely nothing to do with recent GFS ops or for that matter the GEFS.

 

Not Surprised at All.

How many times does the GFS Over do these LP Systems,Even if it does verify as per The 18z it will slowly get corrected Southwards and by Wednesday it will be going through France.

On  Brighter note I am more confident about the Northerly

C.S

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10 minutes ago, cheshire snow said:

Not Surprised at All.

How many times does the GFS Over do these LP Systems,Even if it does verify as per The 18z it will slowly get corrected Southwards and by Wednesday it will be going through France.

On  Brighter note I am more confident about the Northerly

C.S

Not sure i am CS...the update talks of wet weather spreading in from the North west sat/sun.

Sounds ruddy awful.

Oh well....fully expecting a big backtrack very shortly from GFS.

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13 minutes ago, northwestsnow said:

Not sure i am CS...the update talks of wet weather spreading in from the North west sat/sun.

Sounds ruddy awful.

Oh well....fully expecting a big backtrack very shortly from GFS.

Sounds pretty conflicting with most of the models so take with a sizeable pinch of salt, some have the impression they vastly no more than us mere commoners that’s not the case per se.

GFS 00z has began rolling out...

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No real change a smidgen less amplified..our low which may bear snow for quite a few of us is waiting in the wings it seems a tad further north and more shallow compared to 18z.

eek shortwave alert disrupting northerly component making much progress S... 

C782A7E3-BEE9-43E6-8028-1C220FBDDCD1.thumb.png.1651ce652feccc73764967e122419fd5.png

Edited by Daniel*

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Not bad at all T+108 cut off low formed propping amplified zone to NW, still looks like a snowy run for some however I think less so for those further south. Seems a bit of a forecasters headache..

0503D7FE-1EF1-4E0B-A327-B86937A61121.thumb.png.1ac54d072e4c6d472b605bccf7ee1e00.png

Edited by Daniel*

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A much more shallow feature and further north, although this can be a good thing for the white stuff. 

Feeling exceptionally cold at T+132 with widespread heavy ish snowfall on the back edge considerable windchill and blizzard like conditions - this is looking like a good run. 

9693948F-B0C2-4CE4-BA69-55E672102B3E.thumb.png.e9e9b76a26df3772ee30aec976a94874.pngC1DC82E7-4CBA-45D1-BD6F-6C51488E46C4.thumb.png.4758d405a4186826b142a78839057738.png

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Wow very snowy indeed! Heavy snowfall for most...

1A708594-9C0F-4682-9C76-3D66BF368A39.thumb.png.5ff1865b519c251293002e213f9ff73a.png

 

Edited by Daniel*
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3 minutes ago, Daniel* said:

A much more shallow feature and further north, although this can be a good thing for the white stuff. 

Feeling exceptionally cold at T+132 with widespread heavy ish snowfall on the back edge considerable windchill and blizzard like conditions - this is looking like a good run. 

9693948F-B0C2-4CE4-BA69-55E672102B3E.thumb.png.e9e9b76a26df3772ee30aec976a94874.pngC1DC82E7-4CBA-45D1-BD6F-6C51488E46C4.thumb.png.4758d405a4186826b142a78839057738.png

Very impressive run. Pressure charts might not look as good as the 18Z but precipitation charts are a lot better. If only we can see that low drop into europe and a scandi ridge form, that'd be the icing on the cake 

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GFS continues to look awesome- will be some snow around as we head into next weekend ...~(on this run anyway).

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