Model Output Discussion - Spring Has Sprung

[Chesil View]

 Mike Poole

Great post Mike and a good study in how the recent modelling has been underplaying the MJO amplitude by a considerable margin.

I've had the sense over the last two or three days that the NWP is playing catch up and is slightly behind the curve with the speed at which the pattern will change from our current position of positive nao and  Euro hieghts to a euro trough and blocking or wedging to our northwest.

Every so often the ops look like they want to create a winter pattern like 1979 but then back away somewhat which would make perfect sense if they have been under modelling the mjo amplitude.

Edited January 31 by Chesil View

[Rain All Night]

8 hours ago, RainAllNight said:

0z/6z ensemble means, 31st Jan to 15th Feb (day 15)

No change to the expectation of a switch to a cyclonic spell of weather from 8th/9th Feb, and it still appears that after about five days of this, pressure will start to rise again from the southwest. ECM's mean low pressure area is noticeably less intense than that shown by the GEFS (and still has a flatter top), implying that the ECM ensemble members might offer less miserable weather for the UK than the GEFS ensemble members.

0z/6z deterministic runs, 7th Feb (day 7)

The end of the semi-reliable timeframe is still a day or two before the expected pattern change, so the appearance of any "saviour wedges" would still lie just beyond this - unless you ask the ICON.

12z ensemble means, 1st Feb to 15th Feb (day 15)

The most interesting piece of emerging information here is that the rise in heights from the south beginning around 13th Feb is starting to look like it has some potential to manifest as an Atlantic ridge - we'll want to keep an eye on that. For the five or so days before that, it's increasingly looking like we'll need to batten down the hatches.

12z deterministic runs, 7th Feb (day 7)

These few charts are a fair representation of the spread of solutions seen at T+168h this afternoon.

 

[WYorksWeather]

So, let's get the short-term out of the way first. Exceptionally mild for many areas from 2nd-5th, possibly record-breaking if raw maxima are undercooked or Foehn effect is present, as previously highlighted.

It's not all bad news from a cold perspective though. Right on cue with what I've been saying, the ensemble mean signals for the medium term look quite a bit better tonight.

Means are approaching the -5C mark at 850hPa and flatlining for several days, especially further north.

The meteogram for Reading is still largely unchanged, but early signs are better further north. Here's the Newcastle meteogram, which finally shows temperatures by day dropping towards and possibly slightly below average, and the first time in a long while that I've seen it starting to show an increased chance of northerly winds compared to climatology.

I'm not on board with this chase yet properly as the period of interest is still outside the reliable (around the 10th or beyond), and there remain too many mild outliers for my taste. However, this is the sort of upgrading I said we needed to see, so good early steps here.

Looking at the long range, as others have highlighted the EC46 looks better. Probably worth throwing in the CFSv2, which to my mind also looks better than it has of late. Week 2 (7th-13th) sees the Iberian heights weaken and ebb away towards the far south-west of Europe. They are then not restored until Week 4 (21st-27th).

The result is that Week 1 sees a very mild temperature anomaly, which then ebbs away from the north in Week 2. Week 3 is near-normal (possibly a transitional week?) and then week 4 re-establishes the very mild pattern.

Quite interesting what the CFSv2 is doing here - if this verifies, it could be a very topsy-turvy month. The exceptionally mild start is now nailed on, but then we could go into a period with wintry potential, after which the end of the month could bring an early Spring.

Finally, worth noting that CFSv2 anomalies are not directly comparable to the EC46, as the CFSv2 is based on 1999-2010 climatology, whereas the ECM uses a model climatology based on the last 20 years.

 

[Johnp]

Much better dig south of the cold air so far on the 18z

[feb1991blizzard]

 Johnp

Yes, was going to say in all this long range excitement, wondering if 18z GFS was going to get lost.

[Eagle Eye]

 Mike Poole

Great post. Yes models have been under modeling the MJO for a while now,  suspected it was possible as we got close to these phases as well, happy to be right, good to know I understand something well I guess. It's a classic of undermodelling both suppressed and active phases during outside influence. 

"the GFS slightly above but as we go further towards the future, they move very close together and phase 5-7 are more responding to a quickly falling -VE IOD (a fairly strong wave strength response but it's not the only variable, just 1 of the MJO spread inputs) so potentially may be underdoing the strength of the active western Pacific response further away from the western Maritime region slightly infiltrated w/dry air occluded into the far western Maritime region likely in response to the trend away from a +VE IOD, not a full on dry response but not as +VE wet as the normal composite and that dry air into parts of the Maritime region. Whereas a wetter than normal eastern Maritime and western Pacific that has been characterised poorly by the GFS so far. Theoretically leading to a larger response in phase 7. "

The MJO forecast strength during times of extreme IOD change especially but also other outside influences definetely needs to be taken w/many pinches of salt. 

[blizzard81]

 WYorksWeather it's an interesting concept - a month of contrasting halves and weather types. I remember reading Trevor Harleys fantastic weather website years ago which trawled through the historic UK weather archives. It's amazing how so many of the classic bitter cold spells were preceded by very mild episodes..... I'm getting that same feeling right now. 

[feb1991blizzard]

 Lukesluckybunch

or can we.

[blizzard81]

 feb1991blizzard you've just got to love the pub run bless it lol

[blizzard81]

The pub run for some reason wants to blow up a pv lobe over Greenland that wasn't there at all on the 12z run.....thats good news imo. Expect upgrades in the morning. 

[Metwatch]

Watch the low trend into France in the next few days now

[Mike Poole]

It seems to me that the GFS 18z is showing a similar longer term evolution to the ECM and EPS, with the pattern change heralded by the clearing east of the UK of the low at T216 on this run:

[blizzard81]

 Metwatch which is exactly what we want. It's not like the mid Jan experience though. It should lead to consistently low heights over southern Europe and therefore a more coherent cold spell for the UK. 

[frosty ground]

 Mike Poole those Iberian heights look sticky 

[feb1991blizzard]

 blizzard81

This is run of the day - eps 12z p26, brutal cold and an almighty bizzard.

 

https://www.meteociel.fr/modeles/ecmwfens_cartes.php?code=26&ech=192&carte=1&mode=0

 

[blizzard81]

 feb1991blizzard lovin that one.... Feb 91esq....I suspect you liked that spell

[Gowon]

Skinniest scandy ever?

[Uncertainty]

How about this for a mean chart - gem ens - huge signal for the Atlantic to get shut off later in W2…

Meanwhile, the 18z is a mess - but the euro trough is the key here. Get that in place and once the MAR comes we’re in business. 

 

The 46 still so so consistent…

[blizzard81]

 Uncertainty That really is spooky Mr Uncertainty. You posted that just as I was looking at the end of the gfs 12z run which shows this. Mid Feb is looking increasingly exciting. 

[Don]

Has anyone else not been able to view the EC46 this evening?  

[johnholmes]

 Metwatch

Re your comment about heights over Newfoundland.

That area is often close to or withing the main major trough so all the heights show is that the trough is not centred over that area. It is shown east of Newfoundland on the 6-10 and west on the 8-14.

[Daniel*]

The trend is our friend at the moment number of colder runs increasing.  

12z eps yesterday and today for Birmingham.  

[CoventryWeather]

 Metwatch said the exact same thing earlier, more as a question on will it! 

Even next week's slider through Scotland/Northern England could pass further south, often models underestimate how far south the cold air gets as the Greenland high strengthens when time goes on. 

[joggs]

 blizzard81 Not good news it you're of a cold persuasion. You'd like to see heights building there.

[IDO]

Any HL blocking still looks 13 days away, according to the GEM ensembles (D8-16):

The Alaskan Ridge and Icelandic Ridge. It could be engaging with the omnipresent Arctic high, but too far out for specifics.

In the interim, from around D5, we see a low ejected off the ESB that interacts with the jet and sends the jetstream further south, impacting the UK from around D8 as it fills around the UK. GEFS mean D8-16:

The ensembles have a lot of variation and how that transpires on the ground. The 2m temps highlight this (London):

Nothing cold, IMBY, according to the mean. Further north, there may be better chances of a brief spell of below-average conditions before the trough migrates east by D10-11. Fingers crossed, we get the GFS OP take rather than the GEM.