Model Output Discussion - Into February

[sebastiaan1973]

GFS6h could be a reaction of the development in the stratosphere. Research shows that a negative NAO setting is very sensitive to the state of the stratosphere. https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/qj.3280 

[snowray]

Just now, sebastiaan1973 said:

GFS6h could be a reaction of the development in the stratosphere. Research shows that a negative NAO setting is very sensitive to the state of the stratosphere. https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/qj.3280 

Indeed, could this be the turning point we are seeing here? More upgrades in the pipeline? 

[Uncertainty]

We are (understandably) debating the ‘why’ driving the outlook, me included, so I’m going to focus on the modelling for a while… but the last thing I will add wrt the strat is that the euro blocking regime (which we presently have) is the ideal regime for assisting the downwelling and resulting in a GH further down the line - have a look at Domeisen et al (2020) for more details. @Dennishas kindly posted it on Twitter.

Notably, at day 10, the big 3 have significant ridging to the W/NW

 

@Lukesluckybunch it gets awful close mate!

 

We’re trending towards something quite significant end of week 2,  there’s lots of time for upgrades. It feels like it’s all ‘coming together’…

[Lukesluckybunch]

2 minutes ago, Uncertainty said:

We are (understandably) debating the ‘why’ driving the outlook, me included, so I’m going to focus on the modelling for a while… but the last thing I will add wrt the strat is that the euro blocking regime (which we presently have) is the ideal regime for assisting the downwelling and resulting in a GH further down the line - have a look at Domeisen et al (2020) for more details. @Dennishas kindly posted it on Twitter.

Notably, at day 10, the big 3 have significant ridging to the W/NW

 

@Lukesluckybunch it gets awful close mate!

 

We’re trending towards something quite significant end of week 2,  there’s lots of time for upgrades. It feels like it’s all ‘coming together’…

yes weve seen it close many times before..but that chart will do -10 uppers creeping into the east! haha

[Ali1977]

Day 9 mean, well thats an upgrade

 

Id say about 80 percent have us in colder air by next Thurs, obviously a scatter on the set up though. Lots to sort out but the chase is on. 
 

12 hours later most of the U.K. in -4c to -8c uppers with the MEAN!! 

Edited February 14, 2023 by Ali1977

[Allseasons-Si]

Liking the trends this morning

and the gefs are upgrading the Atlantic ridge,...nearly all of them show this at 216

and the 06z mean vs 00z.

summat's in the water

 

[snowray]

Yes big upgrade in the mean, even the control run is much improved.

 

 

 

[Met4Cast]

I think it's best to summarise the broad picture going forward as there's a lot of different things (understandably) being put forward at the moment, some rather complicated things are going on in the atmosphere and sometimes it's better to go back to basics to get a clearer picture of the expected evolution.

High pressure most likely to build out in the Atlantic, GEFS/EPS in agreement. 

 Winds broadly turning N/NWerly next week & during the final week of the month, temperatures falling back to average/perhaps slightly below in the north

Will ridging eventually move north into Greenland? Limited signal for this at the moment, the Canadian vortex could over power any attempts unless we see low heights draining from Canada, will the SSW help us out with that? As such, "deep" cold remains a lower probability until this is resolved.

SSW impacts remain largely unknown re: downwelling, timing & subsequent impacts on the broad-scale tropospheric pattern.

A BFTE is looking unlikely. Any cold weather seems most likely to come from the north, rather than the east. Albeit I see potential for Scandi heights as we go further into March, the likelihood of deep cold lessening the further we go into the month.

Edited February 14, 2023 by Met4Cast

[Lukesluckybunch]

-6  uppers as a mean temperature at 240! 

[alexisj9]

6 hours ago, Mike Poole said:

Liking the movement of the trop PV on the GEM this morning, T144-T240:

We’ve seen something similar in the last couple of runs from the GEM, it’s maybe a little early, but it is what I’m hoping, and indeed, somewhat expecting to see as the SSW makes itself felt…

Almost close enough to take notice of, almost, wonder if it will come closer.

 

[snowspotter]

8 minutes ago, Met4Cast said:

I think it's best to summarise the broad picture going forward as there's a lot of different things (understandably) being put forward at the moment, some rather complicated things are going on in the atmosphere and sometimes it's better to go back to basics to get a clearer picture of the expected evolution.

High pressure most likely to build out in the Atlantic, GEFS/EPS in agreement. 

 Winds broadly turning N/NWerly next week & during the final week of the month, temperatures falling back to average/perhaps slightly below in the north

Will ridging eventually move north into Greenland? Limited signal for this at the moment, the Canadian vortex could over power any attempts unless we see low heights draining from Canada, will the SSW help us out with that? As such, "deep" cold remains a lower probability until this is resolved.

SSW impacts remain largely unknown re: downwelling, timing & subsequent impacts on the broad-scale tropospheric pattern.

A BFTE is looking unlikely. Any cold weather seems most likely to come from the north, rather than the east. Albeit I see potential for Scandi heights as we go further into March, the likelihood of deep cold lessening the further we go into the month.

Like the way you’ve tried to be logical about this but I don’t think at this stage you can rule out winds from the east when the SSW has not really happened yet . We have no idea how it’s going to affect things in next 2 weeks 

[Met4Cast]

1 minute ago, snowspotter said:

Like the way you’ve tried to be logical about this but I don’t think at this stage you can rule out winds from the east when the SSW has not really happened yet . We have no idea how it’s going to affect things in next 2 weeks 

The displacement of the vortex lobe looks to be into Siberia, fairly good agreement/confidence on this, assuming this imprints onto the troposphere below we'd expect to see (as currently being modelled) low pressure dropping into Scandi/Siberia, rather than high pressure. This strongly suggests northerlies rather than easterlies.

The GEM is probably over-doing the amplification here but does give a broad idea of the expected pattern.

[Allseasons-Si]

This dog is liking the look of this...

P16

[phil nw.]

A way to monitor the downwelling of the warmings is to follow the ecm srat. forecasts.

Reversal is underway at the very top and will show at 10hPa in the next day or so.

Lower down at 30hPa the reversal doesn't quite show within the next 10 days,based on the chart from yesterday.

On the plus side zonal winds even at this mid level are forecasted to slow right down,3 to 4 m/s. and this reduction extends right down to the lowest level with forecasts zonal wind speeds down to 7 m/s.

The troposphere pattern should start to reflect this in the later outputs from now with a more ridgy and slowing jet.

Probably why we are just starting to see some interesting charts in the later frames.

[Ali1977]

1 minute ago, Met4Cast said:

The displacement of the vortex lobe looks to be into Siberia, fairly good agreement/confidence on this, assuming this imprints onto the troposphere below we'd expect to see (as currently being modelled) low pressure dropping into Scandi/Siberia, rather than high pressure. This strongly suggests northerlies rather than easterlies.

The GEM is probably over-doing the amplification here but does give a broad idea of the expected pattern.

I think the ECM would be even more amplified than the GEM , so either the GFS has nailed it or we are going to end up colder than that’s showing!!

Understanding the day 10 charts are way off, and lots could change with the SSW happening right now. I’m thinking cross polar flow

[alexisj9]

3 hours ago, bluearmy said:

As soon as the models have reversed flow atop the strat at T0, they respond by finding upper ridging to our west gaining way more  traction than seemed possible only 36 hrs ago (in combination with n pacific sector ridging which cuts the vortex connection across the pole which seemed so strong) 

the zonal flow down here is predicted much slower than had been forecast ….

still too early to get a handle on whether ec/gem ops are too slow and amplified by day 10 and gfs will hopefully sniff the coffee better through its next few runs. But now we have he most important part of what occurring in the upper atmosphere in the starting data, we should begin to get some better modelling of the 8/16 day period. 
 

@nick sussex (and others) have been expecting a change but if the 00z ops are on the money this will be even quicker than expected towards Greenland 

Perhaps,  the high however may be mjo related, perhaps the two could be working together for a change, as the strat will be weeker at the same time as mjo builds heights to our west. So it may be able to push up through greenland.

[Met4Cast]

4 minutes ago, Ali1977 said:

I think the ECM would be even more amplified than the GEM , so either the GFS has nailed it or we are going to end up colder than that’s showing!!

Understanding the day 10 charts are way off, and lots could change with the SSW happening right now. I’m thinking cross polar flow

The EPS mean is certainly of interest, although the high sinks between T216 & T240 this is probably due to the shear number of options appearing within the suite at the moment. 

In any case, if it's cold you're after this is one of the best means in that direction we've seen since December. The SSW is underway, winds have now reversed in the upper stratosphere, that alone is rather exciting regardless of any later impacts!

[Uncertainty]

10 minutes ago, Met4Cast said:

I think it's best to summarise the broad picture going forward as there's a lot of different things (understandably) being put forward at the moment, some rather complicated things are going on in the atmosphere and sometimes it's better to go back to basics to get a clearer picture of the expected evolution.

High pressure most likely to build out in the Atlantic, GEFS/EPS in agreement. 

 Winds broadly turning N/NWerly next week & during the final week of the month, temperatures falling back to average/perhaps slightly below in the north

Will ridging eventually move north into Greenland? Limited signal for this at the moment, the Canadian vortex could over power any attempts unless we see low heights draining from Canada, will the SSW help us out with that? As such, "deep" cold remains a lower probability until this is resolved.

SSW impacts remain largely unknown re: downwelling, timing & subsequent impacts on the broad-scale tropospheric pattern.

A BFTE is looking unlikely. Any cold weather seems most likely to come from the north, rather than the east. Albeit I see potential for Scandi heights as we go further into March, the likelihood of deep cold lessening the further we go into the month.

The trop vortex over Greenland still looks strong at day 11.

I think we’re looking at scandi heights developing late Feb. Obviously the million dollar question would be can we get the strength and orientation right. You can’t rule a BFTE out, that’s for sure, but it still isn’t the form horse. It would only take one more big push from the above northward and things would get very busy in here indeed!

[alexisj9]

More likely would be the PV reducing in strength and slowly drawing west under the high. But it needs to get over there first. This could get very interesting, or not depends on a lot of things still, like where the pv is when the reversal reaches the strat, if the reversal ever reaches the strat, where the high is, and that's just some things.

3 hours ago, nick sussex said:

Do you think we might see the ridge building even more strongly north once the reversal has happened at the lower layers ?

It’s encouraging though that the ECM is developing the ridge within day ten . 

So hopefully a sign of things to come .

 

 

[bluearmy]

I would give the ens suites a few more runs to get a handle on week 2

it’s not usual for them to handle reversed flow  

 

[Allseasons-Si]

That's not a bad mean out to 324 with surface winds from the east,...i've seen a lot worse

06z vs 00z.

[MJB]

 

 

Apologies for the number posted but certainly shows we have something interesting on the horizon , we could see some beauties crop up  in the coming week 

 

[alexisj9]

1 hour ago, mountain shadow said:

Well, I don't know about anyone else, but things seem to be moving as predicted a good few weeks back with the SSW combining with the MJO moving into a favorable phase at the same time. MJO moving into Phase 7 today providing amplification from the Trop as the SSW provides support from the Strat. I mean, what can go wrong?

 

Don't ever say that last sentence again lol, whatever can go wrong usually does for us.

[northwestsnow]

Nice to see the forum busy again.

Would be brilliant to see a late season freeze ,I'm not going to lie,  March snowfall doesn't do it for me but I appreciate it does for some..

One year we will see this kind of SSW in November,that's the holy grail for me personally ..

Fingers crossed we see some cold uppers , defo need those into March when the sun will do serious damage to any snow cover ,unless its a BFTE ,the t would be nice  

[Rain All Night]

Where will we go from here I wonder?