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Paul

Model output discussion - here comes the beast!

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/

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!

Message added by Paul

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Just now, Great Plum said:

What on earth is that showing? Rust accumulations?

Snow and Rainfall

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Breaking news, the 18z maybe in fruitcake land, but the GEFS control is very interesting at T180, is this low really happening in this cold air?

Deep breath!

gens-0-1-180.png?18

gens-0-0-180.png?18

Edited by Mike Poole

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Hands up if you didn't  look at the GFS because u know now SSW did it and all the models are owned 18z :hi:

 

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3 minutes ago, Wardlegacy said:

Model? Time? Day?

I Appologise , I got it from meteox percep future chart.

It looks like what some have said about that low mixing in milder air around its circulation the next slide is even worse.

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4 minutes ago, Nick F said:

Is a close call to whether the low drifts north far enough into England and Wales or stays over France on Friday, a look at the 12z EC MSLP mean for Friday shows it staying over N France, but obviously there’ll be members in there that drift the low further north.

7F89E91E-E31A-4880-BDF5-009CA3B1E008.thumb.png.1bba16bb0b325f0c672a0cad145521d2.png

I think the uncertainty lies, which @Glacier Point touched on, because the low enters Iberia on Thursday under a strong jet which then pushes NE over France taking the low with it, before the jet collapses over France and pushes on east across the Med instead, this leaves the low drifting without a rudder so to speak and therein lies the problem with models with where to take it.

The 500mb cold pool / upper low which drifts SW across the UK mid week and ends up to the SW of the UK later in the week will also play its part in the direction the low takes, because EC and GFS differ in shape and extent of the upper low, they differ where to direct the low, as a surface low will tend to drift withe 500mb contour.

Long way off to be certain on a low track, so more runs needed to see if we are in for a blizzard of the century and perhaps milder air across the S and SE to follow if GFS is to be believed!

 

 

Thanks for your thoughts Nick.

My instinct tells me that surely it would take a well defined steering flow to push a low right into deep cold air, meaning this collapse of NE steering should serve to keep the low from making it right across the UK. Does that make sense or are the beers messing with my scientific sense?

Can’t help but entertain the prospect of a band of snow stalking across S England and then clearing to very slack, clear conditions with temps absolutely plummeting. Both from the point of view of being a fascinating event, and that of it being tragic for some wildlife, homeless people etc. So mixed emotions, but  that’s always going to be the case with the most severe manifestations of weather. It is what it is, for better or worse.

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7 minutes ago, Singularity said:

EPS have a habit of leaning againt ECM right? Even so, a glancing blow at most still makes more sense to me than the low getting right across the UK.

Maybe the low getting across the far south as per UKMO 12z in the most extreme case - but the major letdown of March 2013 has made me completely unable to trust such outcomes at more than a few days’ range.

Having said that, while a halfway house between GFS and ECM remains a very snowy outcome, I will be feeling at least a little positive with respect to that potential event.

Just a whole bunch of potential snow streamers to resolve first...!

Just wondering, what was the March 2013 letdown? A channel low that stayed south?

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8 minutes ago, Great Plum said:

What on earth is that showing? Rust accumulations?

Looks like someone has gone mad with a paint brush...with their eyes closed.

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1 minute ago, Big Snow said:

Just wondering, what was the March 2013 letdown? A channel low that stayed south?

Ohh yes. Hammered the Channel Islands while far-southerners wept into their cornflakes.

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images.aspx?jaar=-6&type=europa.wind.press.arrow&datum=201803031200&cultuur=normal&continent=europa

 

SAT 3/03/2018

 

Again taken from Meteox with that low and its wind directions

Edited by mrmonopoly

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Next week could be traumatic because one man's downgrade on that low is another man's upgrade. High risk indeed but for possibly one of the best snow storms in the 20th century it's worth the risk. Especially for the West and South of the UK who won't benefit as much from the deep cold and snow as others will in the next 6 days or so. To far North and we risk mild uppers but to far South and no one gets anything. So let's go out with a bang and bring on the Snow. Lots of water under the bridge still to we have anywhere near the correct track. Enjoy the Snow evreone :cold:

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1 minute ago, Big Snow said:

Just wondering, what was the March 2013 letdown? A channel low that stayed south?

Singularity is still in therapy over that trauma! :D

Yes it corrected south and hit the Channel Islands and northern France.

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42 minutes ago, MattStoke said:

A low pressure system coming into cold air = The GFS' worst nightmare.

It is truly hopeless with such setups.

 

Agree. Always far too quick with the Atlantic. 0degisotherm.png                   0degisotherm.png                                                                      I'll eat my hat if that cold pool is virtually removed from Europe within 4 days as the 18z shows 

Edited by Zak94

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Just now, mrmonopoly said:

images.aspx?jaar=-6&type=europa.wind.press.arrow&datum=201803031200&cultuur=normal&continent=europa

 

Again taken from Meteox with that low and its wind directions

I’m guessing this is off the 18z gfs run as was the rust forecast? 

My assumption is it won’t be like this - it seems suspect to drag the warm uppers up and ‘blow away’ the cold so quickly...

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Control looks fun for much of the UK with regard to that low end of the week. 

144.png 150.png156.png

162.png 168.png 174.png

180.png

Edited by Mark N

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2 minutes ago, Great Plum said:

I’m guessing this is off the 18z gfs run as was the rust forecast? 

My assumption is it won’t be like this - it seems suspect to drag the warm uppers up and ‘blow away’ the cold so quickly...

It shows the low go across france then approach from the south east and basically sit on top of the midlands for 2 days. I think that is the path the GFS is taking it so yes I would agree with your assumption

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11 minutes ago, Mike Poole said:

Breaking news, the 18z maybe in fruitcake land, but the GEFS mean is very interesting at T180, is this ensemble low really happening in this cold air?

Deep breath!

gens-0-1-180.png?18

gens-0-0-180.png?18

This is absolutely what can happen and the ECM kind of does this - the cold gets so embedded in the low that it becomes a 100% cold low. 

This is what happened in 1991 - very similar set-up - that's what produced the epic snowfalls.

However, this feature won't be nailed until late on. Normally I'd dismiss the GFS because it overblows lows at D6, but the UKMO is with it so have to take seriously.

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11 minutes ago, Singularity said:

Thanks for your thoughts Nick.

My instinct tells me that surely it would take a well defined steering flow to push a low right into deep cold air, meaning this collapse of NE steering should serve to keep the low from making it right across the UK. Does that make sense or are the beers messing with my scientific sense?

Can’t help but entertain the prospect of a band of snow stalking across S England and then clearing to very slack, clear conditions with temps absolutely plummeting. Both from the point of view of being a fascinating event, and that of it being tragic for some wildlife, homeless people etc. So mixed emotions, but  that’s always going to be the case with the most severe manifestations of weather. It is what it is, for better or worse.

As it happens, 18z does have some jet steering flow taking that low north to the UK Friday, the flow weakens through the day and thus dumps the low over us without a rudder.

6DB6D8FD-2E89-49B9-8326-2A5927FA42A6.thumb.png.129f0886a0e7ef9055625a0f5e1805c9.pngD10CE404-5359-4F1A-BACC-512A0C7A0E9D.thumb.png.1f98fe8374f8b25c28e880a9952e46dc.png

Whereas the upper flow is weak and jet is non-existent over northern France and UK on 12z EC, so the low stays over France once dumped by the jet.

17737BAD-1386-4B10-B988-C9C2FA377943.thumb.png.19a774dc50bbce52ef0e60da857ab0cd.png770E6AE3-42F5-45AE-B44C-ED59D62FC700.thumb.png.24828906c3d9d001c063b18a8be1c328.png

 

Edited by Nick F

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Now this is interesting (and what I meant to post last time, sorry as many beers as the 18z!) the GEFS ensemble mean, firming up support for the channel low, this just T180

gens-21-1-180.png?18

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Just a reminder that Carinthian's guidance was that any Atlantic lows would track south and miss the UK entirely. So I would take any of these breakdown scenarios with a huge pinch of salt, especially the 18z GFS which looks just plain daft (+12C 850hpa in Germany). They also conflict with the MetO medium and further range outlooks.

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I wonder if there’s a way of reward with less risk.

It’s possible the low moves a bit further east into Iberia before turning ne so what we see is something like the nor easter in the eastern USA.

The low runs ne with the UK remaining on the cold side. The snow moves ne into the UK but doesn’t change over to rain and  the low becomes absorbed into the troughing over Scandi.

That would be great to see , it’s an unusual scenario but it would be apt given the unusual and stunning depth of cold for this late into the winter .

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BBC just mentioned the 2 computer models about that low pressure either heading into france or direct hit for us. Very interesting times ahead as the models start to flip flop with that low. 

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16 minutes ago, Man With Beard said:

This is absolutely what can happen and the ECM kind of does this - the cold gets so embedded in the low that it becomes a 100% cold low. 

This is what happened in 1991 - very similar set-up - that's what produced the epic snowfalls.

However, this feature won't be nailed until late on. Normally I'd dismiss the GFS because it overblows lows at D6, but the UKMO is with it so have to take seriously.

If that control run comes off , the whole country will be tanked in snow . Is there many ens on the ecm looking like that MWB ? 🙂

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