Model output discussion - 21st Jan Onwards

[stainesbloke]

Just now, feb1991blizzard said:

Yes, I agree, It does eventually become a problem but usually only with showers, even in March, if you get big thick flakes via a slow moving system  and good PPN intensity, theres no problem with it sticking.

I may be wrong of course but IMHO it's all down to air temperatures. It can blizzard in New York, for example, in late Feb and that is at the same latitude/solar insolation level as Madrid. All too often temperatures here are very marginal. But Feb snowfalls and cold spells can be pretty potent, so there's still time for the coldies 

[bluearmy]

NH profile on the gfsp 06z is interesting post day 10 at the time when things also get intreresting high up.  Looks like a pretty swift evacuation of low heights across a swathe  of the NH.  Could be some fun FI's to come on gfs  ops.  

[Frosty.]

If at first you don't succeed, try, try and try again and that is precisely what the Gfs 12z does with several reloading cold shots drawing arctic maritime air south with a wintry cocktail of snow, ice and widespread frosts..good to see and it makes me more hopeful for February to salvage something for all us coldies!

[nick sussex]

3 minutes ago, stainesbloke said:

I may be wrong of course but IMHO it's all down to air temperatures. It can blizzard in New York, for example, in late Feb and that is at the same latitude/solar insolation level as Madrid. All too often temperatures here are very marginal. But Feb snowfalls and cold spells can be pretty potent, so there's still time for the coldies 

With the right set up you can get some very wintry weather. Also sea temps are close to their coldest so less modification. Ice days are still possible even late into February. Its all about getting the right synoptics which so far this winter has been like pulling teeth!

[ColdFront80]

A potential PV split of GFS 12z. Excitement is building.

[Singularity]

Is this the weirdest model output chart of all time?

It looks to be a consequence of the low coming off the U.S. disrupting but then almost immediately merging with a shortwave near Iceland that has refused to run down the western flank of the Scandi trough such as GFS has it doing.

 

Anyway, the suggestions remain of a kind of west-based negative NAO setup emerging and hanging about during 4th-8th Feb, but with uncertainty over just how strongly the heights are able to rise across Greenland.

UKMO has a stronger Arctic High by some margin for +144 (1045 mb as opposed to just 1036 or so).

Consequentially it is not clear how this will interact with lows crossing the U.S. as they eject into the Atlantic having found no coherent polar vortex over Canada to engage with. Trough disruption will be a possibility, but it's not one the models' det. runs are entertaining at the moment.

 

Longer term, GFS is starting to produce some curious looking 500 mb patterns and given that it's still not seeing the tropical forcing properly, the primary reason has to be events in the stratosphere... and there sure have been some interesting changes up there!

 

From the left, we first have the displaced, weakening vortex as of 5th Feb which may be helping with the west-based neg NAO pattern. Then, after a strong bout of warming that peaks 7th Feb, we see the extension toward Canada which was causing some to worry about the return of a notable polar vortex there. After this comes the good stuff, as the vortex splits profoundly by 11th Feb, this setup becoming more pronounced by the end of the run as wave-2 warming starts to become evident (albeit rather weakly).

Based on the lack of organised polar vortex by the end of the GFS 12z at the 500 mb level, it seems to be going for a fairly quick influence on the troposphere. That's typical of a Major SSW. Something to keep an eye on for sure.

[ColdFront80]

In fact it's very cold later in the run. I treat that as fun. This would be freezing.

[bobbydog]

"goodbye mr PV...."

[Singularity]

Forgot to mention, the GWO outlook has changed a fair bit too. It's all connected...

Watch for further adjustments upward and 'outward' to the orbit. Just 24 hours ago it was hardly showing any orbit at all - so typical of GFS.

[Nouska]

The 12Z ARPEGE has resuscitated the idea of a small low crossing southern England - first mooted by the ECM a couple of days ago.

ECM from 12Z on the 27th      

Today's 114 hour ARPEGE      

 

[chris55]

Certainly not a mild outlook into Feb from the GEFS 12z, some snow between the 3rd and 5th further south doesnt look out of the question.

 

[Ali1977]

The next chart could be good, charts are fast becoming much better looking for Feb...Fingers crossed all comes together.

[Cloud 10]

ECM 12z has a chunk of the Polar Vortex visiting the UK.

 

Interesting times ahead for sure.

 

[chris55]

With a chunk of the PV  to our east an Atlantic ridge would be most welcome!

The correlation with the strat is uncanny. Though im not sure if this is just coincidence or whether the strat is really that quick at down-welling.

[nick sussex]

Well the ECM delivers some interesting synoptics but even at T216hrs with what looks like a northerly flow the 850's are not that cold.

With low heights this might mitigate this somewhat but until we see some blocking that's not boxed in over the Arctic then its just cooler and wetter rather than colder and snowier.

Looks okay for hills and mountains, but doesn't pass the crunchy snow and frost test for most of the UK and so therefore it scores 4/10.

Who would have thought at the start of December that we would have sat through so far roughly 240 GFS outputs, 120 ECM and 120 UKMO outputs and whats actually delivered in terms of colder weather is about 7 days with a few hours of slush to show for it for most, a few frosty nights and some poor BBC weather presenter stuck on the North York Moors trying to big up a snowier blip amongst the utter tripe that's masquerading as winter 2015/16.

Ghastly! Theres been more snow in the Middle East and the Greek Islands. For this winter to save itself we need some proper blocking to stop this relentless succession of lows.

And we have now about 4 weeks to save this winter from being a complete write off, that goes down to around 3 weeks when you factor in the solid agreement upto T240hrs.

 

Edited January 29, 2016 by nick sussex

[Frosty.]

Nick's not impressed.. but these are welcome charts from the Ecm 12z, an upgrade on the 00z and this sure beats the hell out of the record breaking mild blowtorch conditions we had through December...hopefully Feb will be a a better month for coldies, it's looking more promising!

[J10]

 

Fascinating for the Alps this week. Snow for the weekend turning to rain. Then Very mild with Freezing Levels hitting 4000m in the west, before turning colder towards the weekend with further snow, certainly not boring. Click the link for more details.

This also shows the GFS's take on the potential colder weather for the UK at times next week.

[Singularity]

56 minutes ago, Nouska said:

The 12Z ARPEGE has resuscitated the idea of a small low crossing southern England - first mooted by the ECM a couple of days ago.

ECM from 12Z on the 27th      

Today's 114 hour ARPEGE      

 

Jolly good spot my friend 

It is the sort of feature that's so small in scale that the usual global models fail to resolve it properly. When ECM was seeing it, the feature was stronger and so it was able to be resolved. I believe ARPEGE runs at a higher resolution, hence it only goes to 5 days ahead? If not, my fledgling theory goes flying out of the window 

 

Looking further ahead, it's interesting that ECM allows just  a bit more time between the storms for the cold air to make it south on the 12z compared to the 00z. Relatively small adjustments to the strength of the jet will have significant implications in this sort of setup when it comes to cold air imports. That ECM is slower upstream than GFS days 7-10 may be related to it seeing the MJO gaining amplitude and moving toward phase 5.

Incidentally, the current nudge into phase 4 looks to be producing results 5 days later that correspond well to the 'El Nino January' composite for that phase:

- but with the strat. displacement enhancing the height increases in the Arctic. I am somewhat relieved to see my predictions bear some fruit, after the models took so long to catch on to the idea. It was starting to strain the nerves a bit!

[chionomaniac]

28 minutes ago, chris55 said:

With a chunk of the PV  to our east an Atlantic ridge would be most welcome!

The correlation with the strat is uncanny. Though im not sure if this is just coincidence or whether the strat is really that quick at down-welling.

Hi Chris you are right and wrong here.

Firstly, the wrong bit - the second chart is a temperature chart and does not show the position of the polar vortex at 10 hPa - so you should not even make the correlation analogy!

The correct bit  ( or partially correct bit) is about the downwelling, or to put it more accurately, the position of the tropospheric vortex in relation to the position of the strat vortex. Yes, this can be well correlated - but not necessarily always ( an example of a disconnect recently was the trop Kara high in early Jan). So when the vortex displaces stratospherically to the Scandi /Siberian sector, then a transfer of the bulk of the tropospheric vortex to this region is quite common. But the best correlation can be seen with a complete split of the vortex from strat to trop. Then we are laughing...

[phil nw.]

The one trend that would help a colder setup is being modeled on both GFS and ECM ops.and that is the jet re-aligning more nw-se with troughing digging into Europe as we go into February.

I wouldn't normally highlight op runs at day 10 but what does catch the eye is their agreement along with Gefs at this range.

 

add the Strat. chart at day 10 at the lowest level(100hPa)from the GFS

and we can see where we are probably heading in week 2 of February,a cooler flow certainly with uppers trending into negative values.

those for C.England.

This would fit in with the colder trend forecast by the MO but we should note colder -at this stage.We need to see better ridging of any Atlantic heights to increase chances of some of that deeper cold further north spreading south nationwide.

It wouldn't need much further amplification at this time of year with the Arctic cold pool to our north now at it's peak extent.

Not a bad trend and it does keep the interest going for cold lovers.

[Singularity]

25 minutes ago, nick sussex said:

Well the ECM delivers some interesting synoptics but even at T216hrs with what looks like a northerly flow the 850's are not that cold.

With low heights this might mitigate this somewhat but until we see some blocking that's not boxed in over the Arctic then its just cooler and wetter rather than colder and snowier.

The issue is that the main thrust of the cold travels from Siberia to the western N. Atlantic via Greenland, where it just serves to boost the development of the storm systems coming our way.

That's where the seasonal changes may help us out as we go through week 2 of Feb, provided we can keep the tropical forcing going. The emerging signs of a SSW would shake things up big time, though. Basically we have two routes to a properly cold setup by mid-Feb but it's going to take something special for the south to join in with the fun. That's where a SSW is arguably more promising. Well, actually the best possible outcome is a SSW working alongside tropical forcing from an MJO event moving across the Pacific toward phases 7/8. Such is up for grabs:

...but even though this is faster than the previous update, it's still three weeks before the optimum setup emerges. In light of that it's a good thing that the models have a real habit of underestimating the speed of MJO propagation in the longer-term. We could do with that wander back into the COD being ditched though.

[chris55]

1 hour ago, Nouska said:

The 12Z ARPEGE has resuscitated the idea of a small low crossing southern England - first mooted by the ECM a couple of days ago.

ECM from 12Z on the 27th      

Today's 114 hour ARPEGE      

 

That little runner caught my attention the other day, good to see it back on the ARPEGE! Snow on the northern edge looks possible although marginal at present.

 

[BLAST FROM THE PAST]

2 hours ago, Nouska said:

The 12Z ARPEGE has resuscitated the idea of a small low crossing southern England - first mooted by the ECM a couple of days ago.

ECM from 12Z on the 27th      

Today's 114 hour ARPEGE      

 

JMA had that yesterday too and UKMO 00z sniffed at it too if you look at my posts so interesting feature.  

 

Come to daddy ECM, mentioned earlier that 00z ECM was decent but could engage in more cold air, and the 12z has just done that.   Lots of tweaking still to come BUT again, turn of month into Feb cold to arrive and we enter the coldest core of this winter.  Cloud 10 mentions chunk of PV moving over UK, yep this is a very volatile cold set up and I think snow will become more and more in the mix....for ALL Uk to be at risk....and to think we had so many posts that winter was done.  

 

 

BFTP   

Edited January 29, 2016 by BLAST FROM THE PAST

[chris55]

4 minutes ago, chionomaniac said:

Hi Chris you are right and wrong here.

Firstly, the wrong bit - the second chart is a temperature chart and does not show the position of the polar vortex at 10 hPa - so you should not even make the correlation analogy!

The correct bit  ( or partially correct bit) is about the downwelling, or to put it more accurately, the position of the tropospheric vortex in relation to the position of the strat vortex. Yes, this can be well correlated - but not necessarily always ( an example of a disconnect recently was the trop Kara high in early Jan). So when the vortex displaces stratospherically to the Scandi /Siberian sector, then a transfer of the bulk of the tropospheric vortex to this region is quite common. But the best correlation can be seen with a complete split of the vortex from strat to trop. Then we are laughing...

Thanks for the info Chiono, always learning

[nick sussex]

9 minutes ago, Singularity said:

The issue is that the main thrust of the cold travels from Siberia to the western N. Atlantic via Greenland, where it just serves to boost the development of the storm systems coming our way.

That's where the seasonal changes may help us out as we go through week 2 of Feb, provided we can keep the tropical forcing going. The emerging signs of a SSW would shake things up big time, though. Basically we have two routes to a properly cold setup by mid-Feb but it's going to take something special for the south to join in with the fun. That's where a SSW is arguably more promising. Well, actually the best possible outcome is a SSW working alongside tropical forcing from an MJO event moving across the Pacific toward phases 7/8. Such is up for grabs:

...but even though this is faster than the previous update, it's still three weeks before the optimum setup emerges. In light of that it's a good thing that the models have a real habit of underestimating the speed of MJO propagation in the longer-term. We could do with that wander back into the COD being ditched though.

Someone on the strat thread had a great analogy which IMO summed up both the strat and the trop. Its like waiting for an elephant to give birth! lol

Until I see a proper block over Greenland or a Scandi high with sufficient cold air to be pushed west then I'm going to be thoroughly underwhelmed.

You maybe right that things might come together later in February if the both the MJO and SSW coincide but I think most are now getting frustrated and impatient. Its not surprising because if they dished out Olympic medals for patience NW members would win gold after gold!

Edited January 29, 2016 by nick sussex