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Model thread discussion - cold spell looming


Paul
Message added by Paul,

It's busy right now, so please ensure you only post about the model output in this thread. 
For local snow discussion and will it snow posts, please use the regional threads
And for more general chat please use the chat, moans and ramps thread.
There's now also a cold spell chat and discusison thread.

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Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

Looking at this d10 chart (gfs 06z and subject to change), we see little sign of forcing. The upstream pattern is very flat, so no Atlantic sector wave. This is def a move away from an MJO response and the wedge we get at d10 seems more a result of the cold block halting the low to our west at d4 and the resultant WAA pushing some warmer air north?

d10 gfs 06z>302999527_gfsnh-0-240(1).thumb.png.37b95064ce8cef1ecb7940a25529e7c1.png

So, possible we are taking a fork here and a new journey? Hard to draw any conclusions as to where this will take us as we have not had many runs for clarity. That is the trend, and again subject to change in the next run or two. Comparing d12 on gfs 0z -v- 12z shows subtle differences can make for better cold evolution:

06z>gfseu-0-282.thumb.png.a436ba0958a8727066d3ecc0f22c9b5f.png 0z>gfseu-0-288.thumb.png.6ca5f8e4c502b2be31bb63cedc011feb.png

At least Thursday-Friday the SW should see a front stall and decay somewhere in that region and many should get some snow!

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Posted
  • Location: Banbury
  • Weather Preferences: Deep Deep Snow causing chaos
  • Location: Banbury
4 minutes ago, IDO said:

Looking at this d10 chart (gfs 06z and subject to change), we see little sign of forcing. The upstream pattern is very flat, so no Atlantic sector wave. This is def a move away from an MJO response and the wedge we get at d10 seems more a result of the cold block halting the low to our west at d4 and the resultant WAA pushing some warmer air north?

d10 gfs 06z>302999527_gfsnh-0-240(1).thumb.png.37b95064ce8cef1ecb7940a25529e7c1.png

So, possible we are taking a fork here and a new journey? Hard to draw any conclusions as to where this will take us as we have not had many runs for clarity. That is the trend, and again subject to change in the next run or two. Comparing d12 on gfs 0z -v- 12z shows subtle differences can make for better cold evolution:

06z>gfseu-0-282.thumb.png.a436ba0958a8727066d3ecc0f22c9b5f.png 0z>gfseu-0-288.thumb.png.6ca5f8e4c502b2be31bb63cedc011feb.png

At least Thursday-Friday the SW should see a front stall and decay somewhere in that region and many should get some snow!

Do you see a push towards Greenland ?  I know this was the thinking ( possibility of ) yesterday 

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Posted
  • Location: Leicester
  • Location: Leicester
8 minutes ago, Battleground Snow said:

Mean and control at 156.

Big scatter on the graph form at day 5. This is a long way from resolved.

 

gensnh-31-1-156 (2).png

gensnh-0-1-156 (3).png

gfs-london-gb-515n-0e (1) (17).jpeg

Another brilliant set control and mean!!

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Posted
  • Location: Liphook
  • Location: Liphook
12 minutes ago, Battleground Snow said:

Mean and control at 156.

Big scatter on the graph form at day 5. This is a long way from resolved.

 

gensnh-31-1-156 (2).png

 

gfs-london-gb-515n-0e (1) (17).jpeg

And of course the 850hpa temps won't tell the whole story, because they may well rise but if we keep a surface flow from the SE (which on the GFS mean looks increasingly possible) then its going to stay substantially colder than the 850hpa profile would imply.

My gut says we will get an easterly based vector, probably a SE or ESE airflow early next week, but the good stuff will stay out of reach for now. I wouldn't be surprised to see a proper attempt at a reload pattern 2-3 weeks down the line from today though, regardless of whether the block sinks early next week or not. If it holds it'll be quite a bit earlier than that.

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Posted
  • Location: Scunthorpe
  • Location: Scunthorpe

Give me each of these runs from the 18z GFS, 00z GFS, 00z GEM and GFS Extended

18z GFS

18zgfscold.thumb.png.44b392c4c8b0eb491ad77e1dc15c9a3e.png

Member 4 is on average the only run that stays below -5 at 850hpa for the entirety of the run and generally below the ensemble mean for most of it and certainly below the long term mean for the entirety. Give me this run from the 18z GFS please

00z GFS

Which run came out as coldest on the 00z GFS

00zgfscold.thumb.png.e86f6632191404bb2ac486baab75a1cc.png

Member 21 is on average the coldest run on the GFS 00z and this one is a true coldies run as it stays below -8 at 850hpa throughout and I would prefer this one over the 18z coldest option

00z GEM

How does GEM compare with the two main GFS runs in terms of the coldest run

00zgemcold.thumb.png.a7a18a5a9ebf7f56a3c7929034156b10.png

The control run comes out on average as the coldest run on the 00z GEM even if it too gets less cold by the end of it. So far not as preferable as the two GFS options but if GEM was the only choice then I'd take it and hope for downgrades to the milder spell later on in the control run

GFS Extended

Now here's a bigger challenge. To find an extended run that manages to stay cold right out to 840 hours away. I went through all of them and deselected those with high or long milder peaks and eventually found one that was quite decent to my surprise

00zgfsexcold.thumb.png.8b94e23865029f7ae25372984b051eb6.png

Extended Member 23 was the coldest run on average and even if it does contain some less cold periods it does remain below the long term mean throughout the entirety of its run and if I was looking long term I'd take this run for the extended cold

 

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Posted
  • Location: Banbury
  • Weather Preferences: Deep Deep Snow causing chaos
  • Location: Banbury

image.thumb.png.f6faf80ea0a6f97eca8b0b7370561e49.png

That monster LP wasn't even in the reckoning on the 0z lol 

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
6 minutes ago, Tim Bland said:

Personally I’d bank the 6z GFS. We get a snowy breakdown next week then a reload with masses of snow potential week 2..what’s not to like ??‍♂️⛄

DE6486E9-1CEB-4805-B564-0364341E5B84.png

Nothing - apart from the timeframe and verification probability, as @Battleground Snow said, 'we need the control to have a long train of low heights to our South' - actually we need it not on the control but on the analysis chart!

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Posted
  • Location: Cardiff
  • Weather Preferences: Day 10
  • Location: Cardiff

Has nobody noticed that the Atlantic is broken?  Up on blocks so to speak.  Factor in good coupling post multiple SSW’s and any “breakdown” just means snow.  We are not having anything mild or zonal for quite some time to come.

the ‘mild period’ is only going to be mild relative to now, which isn’t very mild at all and increasing all members will dip back under the 30yr mean imo.

shortwaves? Bring em on!!!

 

image.thumb.jpeg.c70423ffc43a1586b2407501a65d902c.jpeg

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Posted
  • Location: Springfield, Chelmsford, Essex 30Mtr ASL
  • Weather Preferences: snowy or sunny but not too hot!
  • Location: Springfield, Chelmsford, Essex 30Mtr ASL
2 hours ago, Malarky said:

Apologies for the off topic reply, however, decent convective snowfall so far here today in Nottinghamshire. Feeling hopeful for the runs later today.

Hello Malarky.

Be careful what you wish for.

There is nothing worse than suffering with "the runs"  Make sure you wear bicycle clips just to be on the safe side!

Seriously though and back on topic  the weather in the short term looks good for eastern most counties and from Thursday onwards those in more southwestern parts could join in with the fun with a more organized band of snow away from coasts and particularly with elevation. This is when the uncertainty increases. Will the mild weather plough through. will in the eastern half of the UK although the uppers are warmer with a feed of lower level air off a freezing continent remain very cold and dry, followed by an even colder plunge from the east northeast?

I guess it all depends on the formation and location of high pressure to the north and east of the UK, especially a Scandinavian High which is currently being mooted as a possibility.

What do the more expert on here think will happen? What is their current view as to where FI is?

Kind Regards

Dave

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Posted
  • Location: St Austell,Cornwall
  • Location: St Austell,Cornwall

Seems like a afterthought of the incredible afternoon runs that we have and woken up to this 

Though there's potential for snowfall this Friday there's so much uncertainty from day 5 onwards 

It's disappointing to see but this is British weather in a nutshell 

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Posted
  • Location: Blackwood SE Wales
  • Location: Blackwood SE Wales
47 minutes ago, Day_9 said:

Has nobody noticed that the Atlantic is broken?  Up on blocks so to speak.  Factor in good coupling post multiple SSW’s and any “breakdown” just means snow.  We are not having anything mild or zonal for quite some time to come.

the ‘mild period’ is only going to be mild relative to now, which isn’t very mild at all and increasing all members will dip back under the 30yr mean imo.

shortwaves? Bring em on!!!

 

image.thumb.jpeg.c70423ffc43a1586b2407501a65d902c.jpeg

and according to that double wave , would be a double snow event .. even triple without a real thaw.

It's a big battle .. and we're in no mans land 

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Posted
  • Location: Broxbourne, Herts
  • Weather Preferences: Snow snow and snow
  • Location: Broxbourne, Herts

Big difference in the number of posts on this thread in the last hour compared to the same hour of the day towards the end of  last week!!!

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
5 minutes ago, Timmytour said:

Big difference in the number of posts on this thread in the last hour compared to the same hour of the day towards the end of  last week!!!

Its because the next chance of cold is on the verge of capitulation, the people who are where its snowing now are in regionals, the people who don't probably are confident that they need a miracle 12z suite so are waiting for those, one way another, It will go into overdrive at 1600 hours this afternoon, either for good or bad.

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Posted
  • Location: South Staffordshire
  • Weather Preferences: Snow
  • Location: South Staffordshire
11 minutes ago, feb1991blizzard said:

Its because the next chance of cold is on the verge of capitulation, the people who are where its snowing now are in regionals, the people who don't probably are confident that they need a miracle 12z suite so are waiting for those, one way another, It will go into overdrive at 1600 hours this afternoon, either for good or bad.

Was it even a chance though? There was only a small handful of runs that showed an extension of cold in the snowy/notable sense was on the table.

To me we are heading out of this moderate 'cold spell' into a dry/high pressure dominated spell - unfortunately, this is the wrong time of the year for that to take shape as it will take us out towards the end of February without a true nationwide snow event. 

We need to be looking for ways to increase the chances of a widespread snowy breakdown, to make up for the total non event of this week - certainly in the case of virtually all away from favourable eastern areas. It's a shame this week looks like being 'the spell we have waited for' after everything that's been on the table this winter.

It won't be long before the mildies are out in force with 'Spring' posts.

Edited by PolarWarsaw
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Posted
  • Location: Wakefield, West Yorkshire
  • Location: Wakefield, West Yorkshire
27 minutes ago, feb1991blizzard said:

Its because the next chance of cold is on the verge of capitulation

Really?! That's not the impression I get from the 0z and 6z runs.

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