Model Output Discussion - Into February

[Chesil View]

It would be interesting to know if any research has been done as to whether the time at which an ssw occurs ( ie early,mid or late winter ) has any consequential effect as to whether we get significant cold as a result.  For Instance  of those ssw that do result in cold for the UK  do a higher percentage of early winter ssw produce cold outcomes or are later winter ssw more likely to produce cold outcomes.

[minus10]

From T300 on gfs6z anomaly heights linking up accross the pole...

...probably means very little but just looking for diffrrences in the back end of the run now...

 

[Cambrian]

I’ve been looking at the mean sea level pressure weekly anomalies for the next 6 weeks from ECM. I’ve come to enjoy these of late, and I particularly like the look of this instalment. As we’d expect, they fit in nicely with the weather regimes forecast and are a great place for us to be as we await the tropospheric effects of the SSW event.

Week 1 - European high; Week 2 - Atlantic ridge;

 

Weeks 3/4 - progressively lower heights from Southern Europe and heights building over Northern Scandinavia through Svalbard to Greenland.

 

Weeks 5/6 - northern heights become focussed on the Greenland / Iceland area, while the continuing lowering of heights across Europe through March is a real shocker!

  

This suggests that the reduction in the blocking (red) signal on the regimes chart is most likely only due to the encroachment of lower heights through Europe, fitting with the slack being picked up by the increasing NAO- signal, with a continued suppressed NAO+ signal as we head through to mid-March.

These charts are of course to be taken with a generous pinch of salt as usual because of their extended range, and in this instance additionally because of the potential variability introduced by the SSW itself, but at this stage it does look favourable for the main PV-related trough to drop into Europe with this SSW and that there is a signal for some very interesting and sustained pressure anomalies already in place. 

If we have felt that the Atlantic has been relatively docile this winter (no named storms, etc.), then the charts for weeks 1-3 look to be taking that to a whole new level. Any ocean-driven action even thereafter appears to be well to our south. 

It looks like another protracted period of slow-moving weather, with the UK and Ireland on the northern side of the Atlantic jet stream, scope for northerly winds by week 2 and a predisposition to easterly winds by week 4,

 

potentially for several weeks through March, increasingly unsettled (though not at all mobile) as low pressure pushes up from the south and southwest, and even if not landing anything that extreme from flying PV debris, in any case a more than likely cold end to winter and very slow start to spring. 

[feb1991blizzard]

whitney we have lift off.

[bluearmy]

making a judgment on current output (prob gfs/gefs led because of availability of data but with broad eps support), I think the first reversal around the 15th will not downwell into the lower strat at a latitude which would benefit us. However, a second warming at the back end of week 2 looks like it gives the impetus for the reverse flow to force the strat Canadian vortex extension lower down to dissipate as the strat ridge forces down into the n Atlantic sector. That should mean the Canadian tpv will drift further west and allow a greeny ridge to establish. 
 

of course trop patterns may force a late week 2 cold pattern in any case in the meantime and a pacific ridge into the pole as a QTR is still showing on plenty of ens runs and could be a wild card in general. 

[Johnp]

I guess this (p15) is what we should be looking for based on the teleconnections?

[nick sussex]

More encouraging signs today that the SSW will have an impact especially as there’s two warmings  . It’s like buses , wait for ages and two turn up !

Its hard to say how quick any trop response might be . No matter how good the model factoring in the forecast reversal versus starting conditions once that has actually taken place .

Late February and into early March has often delivered snow in the past although of course we do need to temper expectations with the increase in solar energy .

So it’s really a case of whether we can see a 5 star Synoptic set up , something like 2013 or 2018 or whether we have to settle for something not as exceptional .

I think at this point given the lack of snow for most even a 4 star one will be welcomed .

Edited February 10, 2023 by nick sussex

[Astral Goat Juice]

1 hour ago, Chesil View said:

It would be interesting to know if any research has been done as to whether the time at which an ssw occurs ( ie early,mid or late winter ) has any consequential effect as to whether we get significant cold as a result.  For Instance  of those ssw that do result in cold for the UK  do a higher percentage of early winter ssw produce cold outcomes or are later winter ssw more likely to produce cold outcomes.

So, when it comes to the relationship between SSW and the UK's weather, it's a bit complicated. There's no clear cut answer to whether early winter SSW or later winter SSW are more likely to result in cold or mild temperatures. A lot of factors come into play, like the timing, strength, and duration of the SSW event, as well as the conditions in the atmosphere at the time.

That being said, studies have shown that early winter SSW events tend to bring cold temperatures to the UK, while later winter SSW events are more likely to bring milder temperatures. But it's important to remember that each SSW event is unique and can have different effects on the weather. So, it's really hard to make any concrete predictions based on just one factor.

[Matt Jones]

1 hour ago, nick sussex said:

More encouraging signs today that the SSW will have an impact especially as there’s two warmings  . It’s like buses , wait for ages and two turn up !

Its hard to say how quick any trop response might be . No matter how good the model factoring in the forecast reversal versus starting conditions once that has actually taken place .

Late February and into early March has often delivered snow in the past although of course we do need to temper expectations with the increase in solar energy .

So it’s really a case of whether we can see a 5 star Synoptic set up , something like 2013 or 2018 or whether we have to settle for something not as exceptional .

I think at this point given the lack of snow for most even a 4 star one will be welcomed .

Personally I would want a 5 star one here as neither 2013 or 18 really delivered anything other than a light cover of snow here, obviously though those years did deliver for others, late Nov 10 was the last what I'd call decent snowfall here. So I am hoping for some raging NE/E winds to be showing in the models soon.

[nick sussex]

4 minutes ago, Matt Jones said:

Personally I would want a 5 star one here as neither 2013 or 18 really delivered anything other than a light cover of snow here, obviously though those years did deliver for others, late Nov 10 was the last what I'd call decent snowfall here. So I am hoping for some raging NE/E winds to be showing in the models soon.

That’s surprising given your location . 

Of course aim high . It would be great  to see a 5 star set up.

I was living in France in 2018 so I missed out on the amazing depth of cold the UK had during that notable spell .

There’s still a way to go before we know what’s on offer this time . A lot of things have to come together to get the deepest cold source to hit the UK but certainly coldies are due a change of luck.

[Matt Jones]

It was surprising at the time, in 2018 spell we had it cold  & windy with snow blowing around more than anything but never really got going and in this location we pretty much always avoid anything coming in from the west (storm Emma) so relatively dry here.

[BLAST FROM THE PAST]

5 minutes ago, Scandinavian High. said:

With SSW are we more likely to get snowy Easterly or Northerly what is more likely or could we get both or we could end up mild side.

All of the above.  However, it’s looking like a favourably cold response is n the offing.  

 

BFTP

[Chesil View]

38 minutes ago, nick sussex said:

That’s surprising given your location . 

Of course aim high . It would be great  to see a 5 star set up.

I was living in France in 2018 so I missed out on the amazing depth of cold the UK had during that notable spell .

There’s still a way to go before we know what’s on offer this time . A lot of things have to come together to get the deepest cold source to hit the UK but certainly coldies are due a change of luck.

2018 was a five star epic.

The coldest spell including  days in March  since 1845.

[mushymanrob]

1 hour ago, Astral Goat Juice said:

 

That being said, studies have shown that early winter SSW events tend to bring cold temperatures to the UK, while later winter SSW events are more likely to bring milder temperatures.

Sorry but i disagree with that.

Since 1958 when SSWs were first recorded there have been 13 SSWs in February, only 3 were not followed up by some cold Wintry event. 2018 and 2013 were extreme examples, most post SSW events in Spring were short sharp events.
Cold spells in Spring are common, but the data suggests that a SSW Spring is likely to produce a more severe spell than a non SSW Spring with "normal" cold.

I used the SSW database and Bonacina snow database alongside archive charts for this research.

[Rob 79812010]

17 minutes ago, Chesil View said:

2018 was a five star epic.

The coldest spell including  days in March  since 1845.

[Methuselah]

31 minutes ago, BLAST FROM THE PAST said:

All of the above.  However, it’s looking like a favourably cold response is n the offing.  

 

BFTP

You may well end up being right, Fred. But, in the meantime, maybe we should keep our excitement in check. 

 

[Rob 79812010]

53 minutes ago, Matt Jones said:

It was surprising at the time, in 2018 spell we had it cold  & windy with snow blowing around more than anything but never really got going and in this location we pretty much always avoid anything coming in from the west (storm Emma) so relatively dry here.

We had the blowy snow in Manc all the time and  I thought that was that. Drove home from work one night and saw some cloud drifting over the pennines and we had a 2 hour blizzard! Only time I remember powder snow in Manchester

[Astral Goat Juice]

8 minutes ago, mushymanrob said:

Sorry but i disagree with that.

Since 1958 when SSWs were first recorded there have been 13 SSWs in February, only 3 were not followed up by some cold Wintry event. 2018 and 2013 were extreme examples, most post SSW events in Spring were short sharp events.
Cold spells in Spring are common, but the data suggests that a SSW Spring is likely to produce a more severe spell than a non SSW Spring with "normal" cold.

I used the SSW database and Bonacina snow database alongside archive charts for this research.

Thank you for bringing this to my attention and correcting my mistake. It's great to see that you have conducted your own research and have a better understanding of the topic. Cheers for sharing your findings and you don't need to apologise, we live in a democracy after all (I think)

[MATTWOLVES 3]

So let's just have a little think about it folks...Forget next week it remains on the mild side with rather mundane conditions going on for at least 10 days!

Whats next? SSW is being spoken about a lot right now and for good reason..A full reversal can spell a big shake up of the Northern Hemisphere!

That means we are in the game for some serious action. 

ALERT! The met are now signaling the possibility of widespread wintry conditions towards months end....because basically they are well aware that such an event could up the cold ante by over 60% so it would be foolish to say the conditions will stay the same.

This feels very strange to me as these events are coming literally at the same time as the 2018 one..yes all SSW events can be different...for better or worse...but don't be suprised to see some crazy output appearing this time next week.

Have a gr8 Weekend..and be cool....you be cool...everybody be  

Edited February 10, 2023 by MATT TATTOO

[Allseasons-Si]

Afternoon all,...some good discussions in here today so thanks for that

just my 2 peneths worth to add that we have had a minor warming as we know

*A minor stratospheric sudden warming (SSW) event started at 30 hPa level in the Northern Hemisphere around 26 January 2023(circled in red)*

Climate System Monitoring / TCC

DS.DATA.JMA.GO.JP

---

Climate System Monitoring / TCC

and now we are starting to see a second warming take place,...this will be the start of the one that is forcast to be a major ssw next week and will probably look like (roughly)somewhere where i have drawn the red arrows,you can also see this from the GPH(geopotential heights) chart that @MattH posted some time ago,i am not all that clued up on this chart but would it be right in saying that +ve heights reached at 10hpa?(circled) but i am not sure what standed deviation means,...i would appretiate it if someone would give me and others more clarity on that chart

anyway,...a nuff said about that so here is a couple of 500mb height anomalies of which i am liking at day 15

EPS and gefs do now show +ve heights just NW of the UK with -ve heights to our NE over Scandi and downstream trough Mid north Atlantic,i am not sure of all the +ve heights over Asia to Alaska and what ramifications that will do but i have not seen anything like that before,...ssw induced?

rolling sleeves up for the 12z rolling out now

have a cracking weekend all.

thanks @MATT TATTOO

The latest from met...

Temperatures expected to be mostly around average, but a period of colder or much colder temperatures remains a possibility, bringing widespread wintry conditions.

 

 

 

Edited February 10, 2023 by Allseasons-si
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[Dorsetbred]

1 hour ago, nick sussex said:

That’s surprising given your location . 

Of course aim high . It would be great  to see a 5 star set up.

I was living in France in 2018 so I missed out on the amazing depth of cold the UK had during that notable spell .

There’s still a way to go before we know what’s on offer this time . A lot of things have to come together to get the deepest cold source to hit the UK but certainly coldies are due a change of luck.

Nick, much appreciate your analysis (along with many other learned folks on this thread), BUT, when you use the following I am concerned, you're using a new analysis method. 

QUOTE

change of luck.

/QUOTE

Are you using luck in your forecasting system now?

Of course we have a long way to go, given our experience this winter, so a lot of alignment needed.

[nick sussex]

1 minute ago, Dorsetbred said:

Nick, much appreciate your analysis (along with many other learned folks on this thread), BUT, when you use the following I am concerned, you're using a new analysis method. 

QUOTE

change of luck.

/QUOTE

Are you using luck in your forecasting system now?

Of course we have a long way to go, given our experience this winter, so a lot of alignment needed.

Very funny ! Of course luck doesn’t come into it . We are mere bystanders to what’s delivered .

In terms of the outputs so far .

The UKMO looks the most promising at upto day 7.

The GFS does look like its beginning to feel the SSW love but well into FI .

The GEM is in the naughty corner at day ten . Yuk !

[Ali1977]

The GFS Op may not look great this run but no doubt we’ll get wild swings, there are plenty of GEFS on the 06z showing cold weather starting at around day 9/10, I have a feeling we may go colder early than expected - the UKMO looks interesting.

Lets see if the ENS upgrade again

[Chesil View]

 Perhaps the longer Range modelling is begi ning to  factor in  possible ssw effects The Meto have an interesting tease about the risk of widespread wintry conditions as we enter March in their latest 15 to 30 dayer.

Edited February 10, 2023 by Chesil View

[Allseasons-Si]

Oh!!!,...hello

i will add

i would expect more of a pincer type evolution with the Pac ridge and Atlantic ridge punching further north into the pole as we move closer and closer ,not a garantee however where these will land the CAA to lower lats but it will be fun watching over the next couple of weeks to see how this will go.

Edited February 10, 2023 by Allseasons-si
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