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Model output discussion - mid-winter

Paul

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36 minutes ago, karlos1983 said:

If south of the M4 sees snow next week away from elevation, I’ll eat my hat, usual locations in the North West UK will do well especially with some modest elevation. 

At least it won’t be dull 

4A786254-D610-440A-AC0A-21AF82C0C4A4.thumb.gif.de1c1fce22120da93ea53b8966ef5d95.gif2FB6C805-3E2F-4EE3-97EB-AFE8D6EB3D80.thumb.gif.f309a5fc7b86c140f3a404de44378bf6.gifBE2B0887-FF30-4B7F-905B-26B8E6A0E2C5.thumb.gif.fd2045970da5214d49663305d991064d.gif

maybe I’ll go hunting for snow in the North West..... if I’m welcome that is :rofl:

You might not have to go that far Karlos . I was living in Charminster in Jan 1984 and I can recall at least one snowfall off an identical set up to that forecast for next week. 

 

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So at last the ECM op follows the largest clusters of the previous three ensemble runs and pulls down a colder northerly for D8-D10. 

Potential for a few cold and snowy days especially in the NW!!

And the monster storm of last night had gone, though has it gone from the models for good...

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1 minute ago, Broadmayne blizzard said:

You might not have to go that far Karlos . I was living in Charminster in Jan 1984 and I can recall at least one snowfall off an identical set up to that forecast for next week. 

 

That would be right! When I was a mere 1 years old!! Over due another then 🤪 

I’m going to revert to reverse psychology, no chance of snow  :spiteful:  

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I fully expect a watering down of the cold potential from this nnw set up.  Obviously there will be snow for the more favoured places before any showers die out later in the period, but these maritime setups rarely deliver to wide areas of the country.  I see more opportunities developing later in the month as the wind direction changes with more of an easterly component.

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13 minutes ago, Summer Sun said:

They can start off very cold but as the colder air travels closer to the UK it has passed over relatively warm waters which moderates it

However there is strong 'coriolis effect/forcing in play here(pm-flow)..

And those ISOBARS  are aimed like a snipper at our shores.

This is a notable pm incursion to say the least...and my expect is for no moderation...but perhaps intensification...

Edited by tight isobar
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56 minutes ago, Ed Stone said:

Next week's looking good - for a northwesterly, that is: I think the last times I remember such a depth of cold, from that direction, were in December 1967 and February and November 1973?:D

And on all three of those occasions, snow fell to the south of the M4...:yahoo:

Sorry to appear IMBY but in response to a few posts on here, for the second half of January the south of England has much greater potential to get something out of such a set up than at any other time. M4 less of an issue than in December.

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EDM1-144.GIF?11-0   EDM1-192.GIF?11-0   EDM1-240.GIF?11-0

The trough will move slowly east with the main surface low heading south east into Europe, it looks windy throughout the week but the winds do look like falling light by the weekend, the models placing the low near the UK but with a fairly slack flow over the UK, either variable winds or a northerly with cold air still in place. I would expect it to turn very cold at night by then with hard frosts. Before then the week looks like a mix of sunshine and showers (or longer spells of rain/sleet/snow), eastern areas could see a very sunny week once Mondays front clears though showers can't be ruled out anywhere. There is the chance of heights to our north getting more involved which could pull the winds towards the north east which would be great given that a pretty potent cold pool would be starting to develop towards Scandinavia so a NE wind would be bitterly cold if we get one in the week 2 period.

Overall the outlook looks wintry, not the greatest of set up but pretty good considering we are seeing the kitchen sink literally thrown at the high to our east in the coming week.

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Just a word of caution, Jo Farrows forecast and the chart with it, the ECM mean and the UKV (which showed snow for me Tue, Wed and Thur), now shows heavy rain for at least the first half of that period), are why I will stop short of calling a generally memorable spell of weather, still tweaks either way, I predict Buxton and anywhere generally above 1000ft in the NW will be prone to very heavy falls (in excess of 1ft over the period of next week), places 600ft will get some heavy showers of snow at various points (giving accumulations), anywhere below still could get surprise falls but generally wont be lots of places with significant falls - in short - it will be a memorable spell for some people but not the vast majority of the population and I include the North West in that.

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50 minutes ago, northwestsnow said:

To balance that (although i dont personally recall -10 uppers), its a month on and the seas should be a couple of degrees colder, which will help.

Hopefully.. :)

-12'C  and -13'C uppers from the early December northerly following a pronounced mid Atlantic ridge into Greenland if my memory serves me right.

This set up is completely different though with much more in the way of low pressure, wind and of course it's a westerly.

The Scottish ski resorts will be delighted with the outlook. Alongside the snow enthusiasts up here of course as we're in for a treat! 

 

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Well that was really something; I was wondering if ECM would adjust to the tropical signal much at all, let alone by such a large amount in one run.

From MWB's updates it appears the ensembles picked up on the signal ahead of the operational.

Question now is, are the models only just sniffing the coffee, or at the other end of the spectrum, are we seeing the dreaded overreaction?

One could argue that the window for any overreaction was yesterday when GFS made the move toward the ridging to the west slowing the Canadian trough more and more with each new run. Since then the trend has only been further that way, so confidence is growing in this not being an overreaction... but it's not for sure yet. Nervous times from a forecasting perspective, but not too much so given the key moments are still a week away. 

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would be nice if this came off-

ECH1-240-4.thumb.gif.aefc30a21be056a5a29d38bca50a93b0.gif

ECH0-240-1.thumb.gif.4d95aac672bc6f8d4b3993489bc3440a.gif

that could bring snow right down the spine of the country and beyond.

@feb1991blizzard i was up in buxton and surrounding areas in the summer, on a green-laning weekend. might have to take the disco up there for a little trip! white-laning would be a new experience!

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4 minutes ago, bobbydog said:

would be nice if this came off-

ECH1-240-4.thumb.gif.aefc30a21be056a5a29d38bca50a93b0.gif

ECH0-240-1.thumb.gif.4d95aac672bc6f8d4b3993489bc3440a.gif

that could bring snow right down the spine of the country and beyond.

@feb1991blizzard i was up in buxton and surrounding areas in the summer, on a green-laning weekend. might have to take the disco up there for a little trip! white-laning would be a new experience!

Don't do it next week - or round the higher parts of here - you will get stuck - no ifs ands and buts - you will just run into a 6 foot drift!

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Evening all :)

Birthday watch for tonight - down to T+96 so you'd expect broad agreement:

UKMO:                                                      ECM:                                                       GFS OP:                                                 GEM:                                                       NAVGEM:                                                 JMA:

Modele UKMO - Carte prévisionsgfs-0-96.png?12ECM1-96.GIF?11-0gem-0-96.png?12navgem-0-96.png?11-19J96-21.GIF?11-12

Still some nuances to be resolved - the NW of earlier days has become a WNW or even a W'ly with consequently warmer uppers. The Azores HP is perhaps closer and more influential and the delayed collapse of the Scandinavian HP into Europe has perhaps left less option for a SE'ly move of the LP than was the case a few days ago.

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Evening All ,,! Well the floodgates of hellishy cold weather is set to visit us next week thanks to Greenland  the most potent northwesterly the uk has seen for many years .....:cold:Expect the Winter Rollarcoaster to overflow:yahoo::cold:

h850t850eu-3.png

ecmt850.120.png

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8 minutes ago, ANYWEATHER said:

Evening All ,,! Well the floodgates of hellishy cold weather is set to visit us next week thanks to Greenland  the most potent northwesterly the uk has seen for many years .....:cold:Expect the Winter Rollarcoaster to overflow:yahoo::cold:

h850t850eu-3.png

ecmt850.120.png

Can't understand the posts stating it looks like the most potent/coldest NW'ly in years. December's was colder. People seem to have forgotten it already.

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1 hour ago, doctor32 said:

Is this now the 850 uppers thread? 

Everytime i log on, the 1st post i see contains these. One trend i have seen in these comments is that the upper 850 temps are decreasing though.

So many things over the next week will dictate who gets what wintry wise and the uppers really dont need to be commented on every minute of the day. 

Sorry for the rant but there is much more detail in the upcoming spell of model watching than just the bleeding -4 to -7 uppers

:nea:

Do tell  

Image result for pop corn eating

Edited by stewfox
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18 minutes ago, Nick F said:

The 500mb heights are pretty low across the UK on the models by middle of next week, lowest to the north (see the purples which are below 500 dam), so probably why the air is forecast cold at all levels

h500_w06z.thumb.png.1fc65d2d31e87a01646e7320ee21dc26.png

With regards to whether snow may fall, there are various parameters required. 

Dew point is crucial, needs to be 0C or below

dewp_w06z.thumb.png.3b79a967a41370c38655efc4e91be857.png

Partial thickness between 1000 and 850mb ideally needs to be below 129 gpdm as absolute upper limit

thk_w06z.thumb.png.4e17bf8e55d1a2b627b35ae012480153.png

0C level useful too, don't want too high but looks fairly low next week at this range

iso_w06z.thumb.png.65aba7d39a1def85f4d7509c7763d8d4.png

Finally, wet bulb temperature not any higher than 2C for snow to fall.

wetbulb_w06z.thumb.png.4a825091beb2821601c6ec3bb88e35e9.png

Seem to be ticking all the above for next Wednesday morning, though GFS does have a tendency to have these parameters too low at this range in a WNW flow.

So we will have to wait nearer the time to see if the criteria are likely to be met, but ultimately looking out the window / reports will be the decider!

Looks great for many- but for the ‘south of the M4 posse’ need just a bit more Northerly component would help - ZDL @200M would be better, 400 is to high!!

Edited by Steve Murr
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Moving on from my birthday, how are we looking further down the line ?

GFS 12 Z OP at T+240:

gfs-0-240.png?12

A cold or very cold day with temperatures close to freezing over higher ground and in the north. Further wintry weather likely though fading as the main LP moves away over Europe. A sharp frost from a transient ridge before the next LP approaches.

ECM 12Z at T+240:

ECM1-240.GIF?11-0

More progressive than GFS. The ridge has arrived and it's a fine cold day for all but winds already backing SW over Ireland. 

Worth comparing the NH profiles - the GFS has a very strong HP over NW Russia and the obvious question is whether this can build toward the Pole.

GEM 12Z OP at T+240:

gem-0-240.png?12

An interesting blend. Yes, we have the transient ridge but a nose of LP heading in - will it go SE into France or across the British Isles. There's warmer air wrapped in it which looks to move up against some colder air still over the British Isles.

Very interesting to see what happens one the LP and trough drop into Europe at the end of the next week and certainly very far from any resolution.

 

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13 minutes ago, MattStoke said:

Can't understand the posts stating it looks like the most potent/coldest NW'ly in years. December's was colder. People seem to have forgotten it already.

Much colder higher up though which will encourage more widespread snowfall especially during the heavier showers and any streamers that develop.

It looks to be a rather unstable flow incoming so expect everything including the kitchen sink and especially where you are thundersnow is a strong possibility.

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JMA looks fantastic at 192 BTW.

The potential Atlantic ridge seems to be getting stronger and more amplified with each passing day.

JN192-21.GIF?11-12

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Just to highlight as others have mentioned, the sea temperatures are below average to the North West, which will aid the snowfall potential. I believe the sea temperature has been above average in this area in recent years.

Im personally looking forward to this event, even though I am unlikely to see any significant accumulations.

ecmt850.144.png

It looks like the most potent North West incursion I can remember seeing in recent years

Capture.PNG

Edited by Zakos
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4 minutes ago, Kentish Snowman said:

Much colder higher up though which will encourage more widespread snowfall especially during the heavier showers and any streamers that develop.

It looks to be a rather unstable flow incoming so expect everything including the kitchen sink and especially where you are thundersnow is a strong possibility.

December had uppers at -8 to -10 widely. Colder than anything showing next week.

Not trying to put a downer on things. Just cannot see how it is looking like the coldest NW’ly in years when only a few weeks ago we had a colder NW’l. It’s as if December just gone has been forgotten already.

Edited by MattStoke

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This PM airstream has been very well modelled a fair bit in advanced and some folk say the models don’t have a clue.. I wouldn’t call it exceptional but decent enough to deliver quite widely.

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