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Paul

Please ensure that the majority of your posts in this thread are model related - a theme of model discussion needs to run throughout.
Some off topic chat and reactions are ok, but please use other, more relevant threads for entirely off-topic chat (such as snow reports, met office forecasts and general chat/moans about the weather or this winter).

For more no banter and just model discussion please head to the new focused model thread - this is also a great place to post (or cross post) your longer model summaries or thoughts around the models.

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32 minutes ago, Chertseystreamer79 said:

6th feb...come on frosty...don't panic

It was only 5th/6th Feb when first signs of Beast showed up on GFS!

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Well this run is making a better effort of building heights into Scandi, I know something Blue has been expecting to see

image.thumb.png.c00a95c20bd86a6e36ca51c19a597b71.png

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2 minutes ago, Catacol said:

Exciting week coming. But.....if proper cold is your thing and not marginal NW activity then we are taking significant steps backwards at the moment. The EPS mean for 240h is a long way from anything good

 

 

 

To be honest, deep cold from HLB has yet to materialise for our island unfortunately, so maybe getting some snowfall from marginal setups with PM sourced air is our best bet for now! 

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4 minutes ago, Ice Day said:

Well this run is making a better effort of building heights into Scandi, I know something Blue has been expecting to see

image.thumb.png.c00a95c20bd86a6e36ca51c19a597b71.png

Because or the track of Thursday low as it exits the uk. 

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It looks like we are nearly there!  What to look for in the models

 

I've still very little time to produce a full post, so I'll do a summary.  I'm writing this report for several threads on two weather forums (US and UK) with a full spectrum of readers - so I'll use simple terms. There have been some excellent posts on here in recent weeks and this post will pick up on the timing and coupling issues.


Despite the great advances in our understanding of the teleconnections and how they influence the atmosphere and the broad scale patterns, there are still challenges at certain times in understanding how they interact with each other, constructively or destructively and which ones dominate at particular times. The GSDM (global synoptic dynamic model) pulls this together and gives us a great heads up into what is going on and what we "might" expect and look out for in the coming weeks, months and seasons.  It's just as important to understand what can go wrong and why as it is when everything goes according to plan. 

 

This winter has been both truly fascinating and (so far) pretty frustrating for the cold and snow brigade.  We know that a major SSW (sudden stratospheric warming) and particularly a split SPV (stratospheric polar vortex) usually leads to widespread HLB (high latitude blocking) in the Arctic with a lot of cold displaced towards the middle latitudes. No two SSWs are alike.  Occasionally the wind reversals in the strat never down well to the trop (troposphere), to influence the surface patterns. More often they do produce surface impacts but this can be pretty quickly (in just one or two weeks) or after a protracted period.  These timing issues are mostly in relation to the "coupling" between the strat and the trop.  When they are in harmony, down welling can proceed much more smoothly.  Since the 2018 SSW and the final warming in the Spring, the strat and trop have been pretty decoupled. In fact, it is this which has delayed and prevented (so far) a full El Nino from developing despite a number of attempts and this has defied most of the main ENSO forecasts.  We have seen short periods of El Nino like conditions but with brief La Nina like setbacks.

 

This SSW started off in late December as a displaced SPV which quickly split in early January. The wind reversals in the middle and lower strat lasted for most of this month.  There is a recovery underway up there now (which does not mean that the event is over - far from it) and the reversals are at last down welling through the trop.  It looks like full surface impacts will be seen in the high Arctic within a week or so.  We still need the trop to be receptive (with other teleconnections acting constructively) and it was back in late December but far less so for much of January but the next cycle of tropical forcing has been underway during the last few days. This is where +ve GLAAM (global atmospheric momentum) anomalies push polewards from the tropics. We saw +ve mountain torque events and the GWO (global wind oscillation) is in a higher orbit in phase 6.  GLAAM and the torques are key parts of the GSDM.  Another part of this forcing mechanism is shown by the MJO (Madden Julian Oscillation) with areas of tropical convection progressing from west to east.  This too is entering key phases in its cycle which are more favourable for HLB.  In fact ECM has now joined GEFS (and several other models) with increased amplitude from phase 6 into phase 7 within a few days (indicated on both the VP200 and RMM charts).  There are the usual time lags and the benefits from both the GWO and MJO in favourable phases are usually seen some 7 to 10 days later - ie: on this occasion very much in harmony with the Arctic surface impacts.  

 

There are still two mores ingredients.  One of these is the ENSO state with weak El Nino conditions considered to be most favourable for tropical forcing.  A WWB (westerly wind burst) is underway in the western tropical Pacific and progressing steadily eastwards.  This will be associated with an upturn in the Nino region temperatures which is just getting underway right now.  The final ingredient is FT (frictional torque) which has been stubbornly -ve all month - in fact it was last +ve at the equator and northern tropics in late December.  FT has been rising for the last 3 or 4 days and on the Jan 24th chart (always produced 2 days afterward) it was heading towards +ve territory and is probably already there.  +ve FT really assists with the tropical forcing (caused by the stresses created by tropical convection and changes in AAM).  It should help with the strat/trop coupling down there which may well see this El Nino event finally get over the line with a sustained period of Nino conditions as well as contributing to the overall poleward push of momentum.

 

So, it looks like all this is finally occurring with a much greater degree of harmony.  The AO (Arctic oscillation) is already going -ve and should go more strongly -ve next week with HP showing up near the pole.  The PNA (Pacific North American oscillation) is also going +ve with the Aleutian LP setting up.  The down stream pattern of ridges and blocks then develops in conjunction with the forced extensive HLB from the Arctic.  The Canadian PV should weaken and be pushed further south.  HP is likely to rise in the Greenland area.  Siberian, Arctic and Scandinavian HPs should all be seen at stages and the NAO (North Atlantic oscillation) should at last go -ve.  For Europe and the UK an extended period of north easterlies or easterlies are favoured.  The current LPs with increasingly polar maritime and Arctic incursions in it should be forced southwards or south eastwards.  Given the long SSW event in the strat,, we can expect these surface conditions to dominate for much of February and perhaps well into March too.  Eastern CONUS and Canada should see even more extensive and prolonged cold.  Just how much snow any of us see will be decided closer to the events but all of us should see a fair amount of it.

 

So, once again, I've been very bullish.  I do hope that we do not see another "curve ball" - but this time it does look like our patience will be fully rewarded.  Those with model fatigue need to recharge their batteries. We can expect the models to pick up on these imminent changes increasingly during the next few runs.  In fact there has already been a shift.  UKMO looks to be the most progressive with D6 Arctic blocking (and consistent with their extended outlook).  Exciting times ahead.  David  🙂 

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The North / South type conversations are quite funny actually, especially considering Tuesdays low hasn't even formed in the Atlantic yet and won't for another 18-24 hours yet approx. So anything further into next week is a bit of a lottery still. This can all change at the drop of a hat.

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Really interesting NH profile starting to appear around days 8-9, the PV is all over the show with heights building over Greenland.  Looks like the downwelling from the SSW is starting to have big impacts!?

image.thumb.png.1ecbd61bdefb43d433038bcc974c81c1.png

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32 minutes ago, Tim Bland said:

A good 8hrs of snow with accumulations around 5-7cm in the south / south east. Best so far this winter for widespread snow in this area. It won’t be smowmagedon but enough for a snowman in places 

2A5C6D0C-BB89-4305-B4A3-A9AE88973CBA.png

77B02B3E-4802-4EC9-A394-8F6C822AB907.png

404029C5-951D-4BD4-86D3-214F65417B75.png

Surely a little more than that for 8 hours?

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1 minute ago, That ECM said:

Because or the track of Thursday low as it exits the uk. 

Let's wait and see how the FV3 handles things? Hopefully, not the same way as this!

image.thumb.png.f6f0354b5bb877d4421d4e43cb544289.png

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10 minutes ago, Catacol said:

Exciting week coming. But.....if proper cold is your thing and not marginal NW activity then we are taking significant steps backwards at the moment. The EPS mean for 240h is a long way from anything good

ecmwf-ens_z500a_nhem_11g.thumb.png.3d51d90ad1708070a7b531f5cacb7537.png

making a monkey out of both the MetO long term forecast from a couple of weeks ago and the runs of EC46 which have all supported teleconnective signals pointing to a blocked atlantic and a continental feed via reversal. Strat charts at 240 suggest a jet being dragged south, but no significant signal for a cut off block to the north of the UK where we would want to see disruption of the flow focused.

ecmwf150f24f0.thumb.gif.a1fe8b9ffe4dfbef35068376094baeac.gif

I am ever optimistic, but our winter cold is still side stepping away from the UK and refusing either the develop the -NAO signature that looked significantly likely as we approached mid Jan or develop core cold to the NE. I'm beginning to take ever greater sips from the glass that was most definitely at least half full through all of winter so far but now looking less so.

Meanwhile somewhere in the south looks likely to see snow this week, amounts uncertain, extent to which it will stick uncertain. Perhaps I've got greedy - but "uncertain" wasn't on the menu when looking at winter from a long term perspective early doors. But let's see how it all pans out - upgrades are as possible as downgrades and we aren't into Feb yet.

Yes it seems the attempts have tried to show there hand ie blocking but never fell or developed in the more favourable areas.The se flow hasn't kicked on but as you say who knows going into Feb!!!

Edited by swfc
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Just now, AmershamMike said:

Surely a little more than that for 8 hours?

There’s a good chance Tues early eve starts as rain. So although some areas see precip for 8hrs, 2hrs could be rain and last hour or so will be light and patchy 

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Last time I logged on here was Friday...there have been 66 pages since! 😂😨

I am sure each page has been filled with friendly chat and absolutely no bickering whatsoever! 😁

The main interest for me is Tuesday - lots of heavy cheeky snow showers blowing through! Hopefully they will leave enough on the ground to build a wee snowman! ☃️

Thursday/Friday could be interesting for Scotland if the GFS 6z has it nailed - doubt that very much though! 

Looks very exciting down South with regards to potential significant snowfall - hope it delivers for you all! I know it has been a very tough Winter so far - all the best ladies and gents! Look forward to seeing some great snowy scene pictures in the regional threads soon! ❄️

297F56A1-18B6-4A0F-9F86-FC579D194F61.png

2F51978E-4E2F-40D3-A338-348EC003E484.png

Edited by Mr Frost
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6 minutes ago, Mr Frost said:

Last time I logged on here was Friday...there have been 66 pages since! 😂😨

I am sure each page has been filled with friendly chat and absolutely no bickering whatsoever! 😁

The main interest for me is Tuesday - lots of heavy cheeky snow showers blowing through! Hopefully they will leave enough on the ground to build a wee snowman! ☃️

Thursday/Friday could be interesting for Scotland is the GFS 6z has it nailed - doubt that very much though! 

The great thing about Thursday is that whilst the models all pretty much agree on the broad placement/strength now, the angle of attack makes a huge difference as does the exact shape and the models aren't really going to call that any time soon.

What I would say is at the moment I think the GFS is by far the most northerly model (and that is fairly typical I have to say!) when it comes to the front, most models are a solid 50-100 miles south with regards to the northern extent, however still plenty of time to come on that one and I'm sure you'll be getting plenty of snow showers/troughs .

So all to play for still for sure!!

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Gfs para further south with the low!!just keep an eye on euro4 now!!

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20 minutes ago, Catacol said:

Exciting week coming. But.....if proper cold is your thing and not marginal NW activity then we are taking significant steps backwards at the moment. The EPS mean for 240h is a long way from anything good

ecmwf-ens_z500a_nhem_11g.thumb.png.3d51d90ad1708070a7b531f5cacb7537.png

making a monkey out of both the MetO long term forecast from a couple of weeks ago and the runs of EC46 which have all supported teleconnective signals pointing to a blocked atlantic and a continental feed via reversal. Strat charts at 240 suggest a jet being dragged south, but no significant signal for a cut off block to the north of the UK where we would want to see disruption of the flow focused.

ecmwf150f24f0.thumb.gif.a1fe8b9ffe4dfbef35068376094baeac.gif

I am ever optimistic, but our winter cold is still side stepping away from the UK and refusing either the develop the -NAO signature that looked significantly likely as we approached mid Jan or develop core cold to the NE. I'm beginning to take ever greater sips from the glass that was most definitely at least half full through all of winter so far but now looking less so.

Meanwhile somewhere in the south looks likely to see snow this week, amounts uncertain, extent to which it will stick uncertain. Perhaps I've got greedy - but "uncertain" wasn't on the menu when looking at winter from a long term perspective early doors. But let's see how it all pans out - upgrades are as possible as downgrades and we aren't into Feb yet.

Hi catacol 

The ext eps are not looking great but that said they have looked great for weeks in the extended and haven’t delivered anyway . Hopefully something will just come up in the mid range around days 7-10 . I’ve lost faith this winter in all long range models tbh lol . 

Cheers . 

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Low further south on GFSP compared with its previous runs...

gfs-0-54.png?6

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2 minutes ago, Cold Winter said:

Low further south on GFSP compared with its previous runs...

gfs-0-54.png?6

And heads se as opposed to gfs👍

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18 minutes ago, Bring Back1962-63 said:

 

So, it looks like all this is finally occurring with a much greater degree of harmony.  The AO (Arctic oscillation) is already going -ve and should go more strongly -ve next week with HP showing up near the pole.  The PNA (Pacific North American oscillation) is also going +ve with the Aleutian LP setting up.  The down stream pattern of ridges and blocks then develops in conjunction with the forced extensive HLB from the Arctic.  The Canadian PV should weaken and be pushed further south.  HP is likely to rise in the Greenland area.  Siberian, Arctic and Scandinavian HPs should all be seen at stages and the NAO (North Atlantic oscillation) should at last go -ve.  For Europe and the UK an extended period of north easterlies or easterlies are favoured.  The current LPs with increasingly polar maritime and Arctic incursions in it should be forced southwards or south eastwards.  Given the long SSW event in the strat,, we can expect these surface conditions to dominate for much of February and perhaps well into March too.  Eastern CONUS and Canada should see even more extensive and prolonged cold.  Just how much snow any of us see will be decided closer to the events but all of us should see a fair amount of it.

 

 

Lets hope your right because at the moment the GEFS out to +384 suggest the opposite for much of Europe & UK. See my previous post on the GEFS 850hpa means across various locations. The theme at the moment is to keep the very cold air bottled up in the Arctic.

The GFS Op is a good example.

GFSOPEU06_276_1.png

Based on current output we would be waiting till mid Feb!

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Yep South East England has a yellow warning Tuesday evening for snow and now looking like the low on Thursday is trending south with a risk of more snow ..

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i see now at 87 hr  we got two more lows  in the north sea

icon-0-87.png

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