Model output discussion 14/04/18

[northwestsnow]

EC looking really good this morning- infact the azores high is gaining strength with each passing run it seems.

I suspect that run would be producing some decent temps across southern parts- mid 20s?

 

[Djdazzle]

4 minutes ago, northwestsnow said:

EC looking really good this morning- infact the azores high is gaining strength with each passing run it seems.

I suspect that run would be producing some decent temps across southern parts- mid 20s?

 

It was looking really good at 192, then the next two charts seem a bit odd because they seem to retrogress the ridge.

[Summer Sun]

The good news this morning is the unsettled spell looks relatively short lived

[mb018538]

1 hour ago, Djdazzle said:

It was looking really good at 192, then the next two charts seem a bit odd because they seem to retrogress the ridge.

I wouldn't worry about finer details at this range....only a couple of days ago it appeared low pressure would be more dominant and we would have to wait for any high pressure influence. If that can quickly change, then charts at D8-10 aren't going to be accurate at all. I always say get the high pressure build in first, then worry about that later.

[summer blizzard]

Euro is perhaps a bit overstated in that it's more or less a 3 day ridge in terms of proper ridging from days 7-9 however yes, it does look more like a N/S affair post day 6.

Edited June 12, 2018 by summer blizzard

[Frosty.]

The Ecm 00z ensemble mean is another step in the right direction towards a warmer more settled spell returning..very nice trend.

[stodge]

Morning all

A return for the morning medium term analysis from me. After a synoptically fascinating late winter and spring with the latter starting with an incredibly cold spell and ending with one of the warmest and sunniest May months for decades, where does summer go from here ?

It's actually quite cool and uninspiring in London Town this evening but where will we be on or around Midsummer (at least in solstice terms) ?:

ECM 00Z at T+240 (Friday June 22nd):

A typical summer chart for NW Europe with the Azores HP ridging strongly NE and a weak jet held well to the north. Decent conditions - warm but not hot with a gentle NW'ly flow and always the risk of damper and murkier conditions on western coasts and hills.

GEM 00Z OP at the same time:

Much more solidly anticyclonic with the ridge over Ireland and NW Britain so a cooling NE'ly breeze for southern and eastern areas meaning it's pleasant rather than oppressively hot.

GFS 00Z OP at the same time:

The Azores ridge has a more easterly tilt so crosses southern parts with most of the British Isles covered by a balmy WSW'ly flow. Fine and warm especially in the south but cloudier and mistier to western coasts and hills.

GFS 00Z Parallel at the same time:

Not hugely different from the OP.

GFS Control at the same time:

Closer to the GEM.

In summary, it's quite settled vs very settled as we move to the end of next week and those attending the last couple of days of Ascot should be fine in their finery (so to speak) with comfortable to warm temperatures but nothing excessively hot or humid on offer. Dry for many if not most but western coasts always vulnerable to a muggier Atlantic and some drizzle and low cloud at times,

It's not very interesting synoptically in all honesty but it's summer weather - beyond that the question is whether the ridge relaxes back SW or cuts away to the NE and that might be of much more interest.

[Guest]

Gfs 06z a step backwards and the ridging from the south west struggling to build any momentum and quickly collapses back opening the door to the Atlantic from the north West. Maybe a one off or an outlier not great viewing. 

[Djdazzle]

2 minutes ago, Alderc said:

Gfs 06z a step backwards and the ridging from the south west struggling to build any momentum and quickly collapses back opening the door to the Atlantic from the north West. Maybe a one off or an outlier not great viewing. 

Probably an outlier. Evolution looks a bit iffy.

[Singularity]

ECM seemingly playing the usual game during times of Pacific tropical forcing; underestimating the downstream impact on the patterns around the UK and having  to correct slowly but surely toward the other models as a result.

I say seemingly as I’ve known the models to play tricks on me before .

[Guest]

2 minutes ago, Djdazzle said:

Probably an outlier. Evolution looks a bit iffy.

Why does it look iffy? Its a solution that has played out many times before. 

[Djdazzle]

12 minutes ago, Alderc said:

Why does it look iffy? Its a solution that has played out many times before. 

It seems to spawn a LP system and deepen it a bit too enthusiastically, which is a known GFS trait.

[Guest]

2 minutes ago, Djdazzle said:

It seems to spawn a LP system and deepen it a bit too enthusiastically, which is a known GFS trait.

On the contrary, the evolution of that low is really not much more different than that of later this week so a definite possibility and one of the reasons several people including myself have been extremely cautious of the progged north east extension (or potential lack of it) of the Azores high into the middle part of next week. 

[Djdazzle]

It’s way out into FI though. Not overly concerned yet.

[Frosty.]

The Gfs 6z operational is probably best described as a changeable run with a mix of settled / unsettled spells, the settled spells mostly across southern uk where it also looks pleasantly warm for most of the time with temperatures into the low 20's celsius range.

[Guest]

The mean of the gfs 06z ensembles pretty much wobbles either side of the LTA so not the worst pattern but definitely nothIng to suggest a return to anything very warm and particularly sunny.

[mb018538]

Wouldn’t worry too much, the 6z and 18z are pretty much ignored by met professionals due to the lack of data compared with the 00z and 12z runs.

[Frosty.]

I think the GEFS 6z mean shows a considerable improvement in our weather next week, at least for the southern half of the uk with increasing azores high / ridge influence and temperatures gradually rising too, especially further south where it becomes rather warm.

Edited June 12, 2018 by Frosty.

[jam]

1 hour ago, mb018538 said:

Wouldn’t worry too much, the 6z and 18z are pretty much ignored by met professionals due to the lack of data compared with the 00z and 12z runs.

I thought it was different data not necessarily less data? 

[Guest]

26 minutes ago, jam said:

I thought it was different data not necessarily less data? 

And its more up to date data.......

[mb018538]

00z and 12z have 10-20x more land sounding data readings fed in than the 06z and 18z - which is one of the reasons they tend to verify as more accurate.

@jam this is also true, the 18z actually used to have around 25% more data inputs than the 12z (generally aircraft data), but it's the lack of ground readings which give it lower accuracy.

Edited June 12, 2018 by mb018538

[Mike Poole]

26 minutes ago, mb018538 said:

00z and 12z have 10-20x more land sounding data readings fed in than the 06z and 18z - which is one of the reasons they tend to verify as more accurate.

@jam this is also true, the 18z actually used to have around 25% more data inputs than the 12z (generally aircraft data), but it's the lack of ground readings which give it lower accuracy.

This claim is often made on here but whenever I check the verification statistics, it never seems to be really borne out.  The differences between the 4 runs at day 5 are not statistically significant, I would suggest. 

[mb018538]

Perhaps things are ever improving and the gap narrowing - that used to be the case. Those stats still show the 12z top of the tree, which it always has been as far as I know!

[Tamara]

Evidence keeps growing through this early summer period that fine warm weather patterns may defy previous years - and rather than vanish off the map, instead increase in frequency and duration as time progresses

1) A convectively coupled kelvin wave (CCKW) is actively core punching the La Nina trades in the eastern Pacific with signs of westerlies also replacing La Nina trade easterlies at the dateline

 

2) Active MJO activity has persisted for some considerable time and is looking set to return quickly to the Indian Ocean for another eastward orbit - very much on the accelerated periodicity (timeline recurrence) side of the envelope.  I wouldn't be taking amplitude and progression from the Wheeler and Hendon plots too literally at face value this early on because the deterministic models become quite unreliable in terms of "seeing" eastward propagation of tropical convection and tend to undercook it the further out in time. There is the ultimate suggestion of eastward progression back to the Pacific into July anyway which implies rising AAM.

 

Edit: Two plots have not appeared for some reason..

The absence of lack of future activity suggests a reduced time for atmospheric angular momentum to fall back in the "lull phase" that is just starting - and in addition to the trades in the Pacific apprehended (as above)  implies further westerly winds to be added in due course across the tropics, with jet extension into the Pacific from Asia promoting further programmes of downstream anti-cyclonic rossby wave breaking

3) The CFSvs 2 receives some dubious feedback for its NWP projections, but in terms of atmospheric signalling in my experience it proves a valuable trends ahead model. It has been consistently advertising the now occurring downturn and next uptick in relative angular momentum tendency to centre somewhere around 23rd June - maybe a day or two later.

This fits the next referenced MJO tropical cycle activity and it also acknowledges the consistent warming of the Equatorial Pacific as assisted by the current surge in convective/cyclonic activity linked to both the concluding MJO wave and especially the CCKW east of the dateline

4) Furthermore, a latest CFSvs2 forecast is for a reversal of atmospheric state from La Nina to a more El Nino like circulation through July. Whilst the timing of any future El Nino state is open to question, the general atmospheric trend suggested is given credence reflecting the shifting sands occurring in the Equatorial Pacific and also fits the next expected upward trend in AAM tendency starting later this month increasingly into July.

Synoptically this supports extended NWP ensemble data and increasing hopes for further ridging across UK and rest of Western Europe. Assuming this trend, then natural  seasonal wavelength changes into the heart of summer would fully augment this atmospheric trend with potential for increasingly very warm/hot spells

 

The shorter/medium term lull endorses the more unsettled/split pattern with the Azores High influence mostly restricted further south and, based on lower angular momentum lag, best not to be surprised by any modelling showing reluctance for the ridge to migrate too far east as initially suggested.

However, far from a bad outlook and the further time progresses, then the greater the percentages increase for ridging to gain proper eastward and northward ascendancy for the greater part of the UK.  As often stated, making suggestions for possible outcomes is much better suited to me than making forecasts, but based on steady continuing supplies of evidence, its not unreasonable to be quite optimistic most especially for July prospects to build on the extended spell of fine weather that is currently breaking down, at least just for the time being anyway.

 

 

Edited June 12, 2018 by Tamara

[Guest]

8 minutes ago, mb018538 said:

Perhaps things are ever improving and the gap narrowing - that used to be the case. Those stats still show the 12z top of the tree, which it always has been as far as I know!

Also the pub run really needs to loose that tag as it out performs the 00z and 06z run.