Model output discussion 14/04/18

[Frosty.]

Looking at the GEFS 00z mean, it's a hot start to the week across the south, tuesday is the coolest day if you can call low to mid 20's c cool!! and then from wednesday it starts hotting up again..throughout the week ahead shows high pressure / strong ridging and plenty of sunshine. Looking at the extended outlook, although it shows lower heights to the NW and less azores high / ridge influence it still looks like a north / south split with southern uk and especially the southeast never cool with temps between 23 / 25c and although a bit more changeable, it's really the far NW which looks coolest and most unsettled beyond the next week / 10 days ahead.

Edited July 8, 2018 by Frosty.

[mb018538]

The ECM ensemble mean is pretty favourable at 144:



By day 10 not looking so good:



By day 13 full on cyclonic westerly:



ECM has been flip flopping a lot recently. The 00z isn't great after next weekend, whatever way you look at it.

[summer blizzard]

On top of the Euro0z the GFS6z also illustrates my point well..

At day 7 we go sub-1020mb as the upper ridge fades..

At day 8 the front passes with little fight..

[Frosty.]

The Gfs 6z operational shows predominantly settled warm / very warm weather during the week ahead, hot at first in the south, then temps dip a little on tues before rising again from midweek to and including next weekend when some areas become hot again, there's eventually an increasing risk of isolated heavy showers / thunderstorms developing. The following week shows some heavy rain around but still with sunny spells, warm / very warm temps and quite humid further s / e with a slow moving trough to the west and warm air pumping north ahead of it..it takes until deep FI for the trough to move east over the uk. I would say there's plenty more of this very summery weather to come during the next 7-10 days and even beyond that could still be pretty decent, at least further south.

 

Edited July 8, 2018 by Frosty.

[Fourty Point Three Degrees]

 

1995? 1976? Yeh right.

 

Edited July 8, 2018 by 38.5*C

[Dominic Carey]

A great run yet again for the next 10 days despite a slight drop off in temperatures later in the run

Edited July 8, 2018 by Dominic Carey

[danm]

28 minutes ago, 38.5*C said:

 

1995? 1976? Yeh right.

 

Even 1995 and 1976 had their cooler, wetter spells. We can't expect 3 months of heat and sunshine in this country. 

A wetter spell does seem more likely after next weekend, however who's to say August won't see the heat return? 

Edited July 8, 2018 by danm

[Man With Beard]

40 minutes ago, 38.5*C said:

 

1995? 1976? Yeh right.

 

Also a chance the storm will encourage heights ahead of it and then stall behind them - which could lead to a plume. 

Looking less certain in general that the SE will turn that unsettled in the next two weeks now - a short pause at best (worst?) on most ensembles. 

Further out on the ECM extended, by D15 most runs put the SE close enough to euro heights to continue enjoying useful summer weather. Less certain in the north. Also signs of a Scandia ridge developing on many runs. 

Edited July 8, 2018 by Man With Beard

[mb018538]

That could happen - pretty unlikely at the moment, best I can find that matches that evolution is P3 from the 6z ensembles (warm outlier) which stalls the low out west so that by day 10 it's dragged a plume up:



It actually stalls the low and locks in the heat right through to day 15 too.

[Derecho]

52 minutes ago, 38.5*C said:

 

1995? 1976? Yeh right.

 

Lol so you can forecast the rest of the Summer now?

2018 is far warmer then 1995 at this point and also drier. 1976 was hotter but that had an exceptional first half to July. The second half of July 1976 actually saw average temperatures.

Hurricane Chris could well prolong things as its forecast to go through Newfoundland and then towards Greeenland. This could actually lead to yet another ridge of high pressure moving over the UK ahead of it.

We have had an exceptionally sunny and dry first half of summer. It will be the 4th warmest first half to Summer on record if it transpires. What more do people want?

1846 and 2006 were warmer but had poorer second halves. If the high pressure pattern continues we could surpass 1976.

[Portland Paul]

1 hour ago, danm said:

Even 1995 and 1976 had their cooler, wetter spells. We can't expect 3 months of heat and sunshine in this country. 

A wetter spell does seem more likely after next weekend, however who's to say August won't see the heat return? 

We can't expect 3 months of heat and sunshine in this country, but it is still possible. Especially if any Atlantic interference in mid range and FI continues to be pushed back or be aborted time and again! My money is on many more weeks of high pressure and heat! 

[BruenSryan]

This is the sea surface temperature anomaly map for July 1995 that I'm referring to @Mike Poole.

As for Chris, let's have some perspective. Let's look at two examples of very deep lows/storms in recent times coming towards the UK and Ireland; ex-hurricane Cristobal on 31 August 2014 and "Irene" (as apparently named by the media) on 16 April 2018. Both lows promoted ridging over us. The first one, Cristobal, gave away to one of the driest Septembers on record in our countries with barely any rainfall for a lot of places for much of the month following a very wet end to Summer 2014. Meanwhile, Irene gave away to an exceptional warm spell for the time of year and later, a very dry May along with a very dry June with lots and lots of high pressure being the dominant influence. Same could happen with Chris this time in prolonging the settled weather again with it helping to ascend more high pressure from the south (which will be bad news for some, especially here in the east of Ireland where I live). The Azores High is still very strong and ridgey. Add the fact that the GFS was "toying" onto this idea too yesterday well in FI on some runs. I would not be surprised whatsoever if this was to actually happen given how the Summer has turned out so far and with reasons above given light. You could also consider Hector of mid-June.

Edited July 8, 2018 by BruenSryan

[Mike Poole]

I think tonight's 12 suite will be interesting, it looks settled until next weekend but what happens next is just out of the reliable timeframe for the models.  UKMO looks decent as far as it goes, but the interesting times are later than that, T144:

ICON out to T180 has the NW / SE split option:

only the other day I was saying that a tropical storm might upset the pattern, and now we have one in Chris, but it might equally well reset the pattern.  Lots of interest in the model output at the moment.

[Snowy L]

12z looks like an improvement to me. Much more straight up west to east movement of the low instead of NW to SE.

 

12z                                                             06z

Yep Low exits to the northeast of Iceland. Honestly if we manage to wriggle out of this breakdown then this summer approaches legendary status.

 

Edited July 8, 2018 by Snowy L

[Frosty.]

The ukmo 12z is sweet, now that's what I call a happy ending, much better going forward compared to the 00z and yesterday's 12z!..largely fine with plenty of sunshine and hotting up again!

[mb018538]

TS Chris still causing lots of headaches.

UKMO takes it up the eastern seaboard, where it dissipates - opposite to the ECM run. What I don't like is that it pumps a lot of WAA up the western flank of Greenland, which could build heights there and send the trough down towards us, which is where I think the UKMO run would head.

GFS whistles it across the Atlantic, and actually looks heaps better as it stays well to the north, turning things pretty hot again by next weekend:

Edited July 8, 2018 by mb018538

[Singularity]

 

GFS 12z brings the angle of the jet stream more in line with the ECM 00z for Friday.

The track of ex-Chris is, however, different; further north, such that it merges with the Atlantic trough to our NW as we head into Saturday;

 

Note the jet stream orientation and latitude - still SW-NE and tracking north of the UK. Quite different to what we had before;

...but this sort of thing remains a possibility if Chris tracks further south, though I'd be surprised if the trough was orientated in the same way. Take the 12z orientation but 06z ex-Chris track and you have the 00z ECM, more or less.

 

There remains much calamity in the modelling when it comes to resolving how the pattern will adjust during the middle part of the month. @Captain Shortwave surprise at the scarcity of runs digging a trough down to the west of us and Europe is well-founded; this is the sort of thing the El Nino imprint should encourage.

My diagnosis of the struggles we're seeing is that the anomalous trade wind burst in the C Pacific is essentially leading to a 'can't see the wood for the trees' situation. In reality, that's only a relatively small event in the face of a large-scale change of atmospheric state. It might yet give the Atlantic trough an opportunity to reach the UK for a time, but a prolonged impact from such a system would contradict the base state, so making it hard to justify expecting such a scenario over an 'interlude' preceding a return to drier conditions for the south in particular.

 

Oh and, just so that things don't seem too straightforward, there's still the uncertainty as to just how much the unusual N Atlantic SST configuration is encouraging pressure to remain high between the Azores and Scandinavia even when we'd usually see an interruption to that setup. It really is fascinating to see things unfold in this regard!

[Mike Poole]

GFS 12 z is a decent run. Better than many in the last couple of days, preserves the ridge longer, good to see as we enter this period of increased uncertainty.  Here to T192:

[shaky]

Wow an absolutely fantastic set of 12zs from ukmo and gfs this afternoom!!heat just keeps going on and on with high pressure over the uk and lows going over the top!!this really is remarkable!!

[Djdazzle]

8 minutes ago, shaky said:

Wow an absolutely fantastic set of 12zs from ukmo and gfs this afternoom!!heat just keeps going on and on with high pressure over the uk and lows going over the top!!this really is remarkable!!

This is why I keep saying that until the breakdown is modelled at T120 or less, I’m not convinced. Doesn’t matter what the EC15, EPS or whatever say because they are all susceptible to large scale flips.

[Tamara]

On ‎02‎/‎07‎/‎2018 at 18:42, Tamara said:

 

.... its worth repeating again the limitations that NWP has in terms of its systemic biases and difficulties modelling tropical convection and momentum processes, often missing more micro scale flare-ups (such as recently and on-going in the Pacific) which mean that the cyclical MJO accounts for a surprisingly smaller amount of the tropical forcing budget that influences the atmospheric circulation....

 

...without consideration of the extra tropical momentum budget (i.e slow moving blocking patterns such as we have seen for many months) - and which in itself NWP do not always resolve quickly. .

Its this that makes July especially interesting with the potential July>August signal in mind in term of the processes likely to happen across the Pacific which imply a further surge of atmospheric angular momentum and next phase of rossby wave dispersal to top up blocking patterns.

Persistently warming sub and surface water anomalies in the Pacific look set to augment an ocean kelvin wave with an atmospheric MJO related kelvin wave sequence through July (in addition to micro scale cyclonic typhoon activity) which suggests a correction ahead to AAM and consequences for what happens to the existing pattern..

 

Frictional torque leads mountain torque tendency as rossby wave dispersion travels to the extra tropics. 

A return to a Pacific jet extension, further out, means the profile of the Pacific becoming increasingly cyclonic first and foremost (there is already typhoon activity in the Western Pacific) and then with time the downstream pattern reflecting this adjusted wavelength with a corresponding greater trough tendency in the Atlantic to our west. (And, as a future possible heads-up, NWP will quite likely be progressive with such a signal and try to blow out the blocking).

So, in this scenario (should it come to pass as evidence helps support) less domination of the Azores High likely - as a non-forecaster I might still indulge in also quietly suggesting that our friendly summer High becomes more continentally and Scandinavian orientated with emphasis of ridging from this central focus rather than from the SW. This leaves open the door for greater influence from heat from a southerly vector mixing it up with troughs attempting to undercut the heat. So maybe a more thundery aspect coming into the second half of summer at the same time perhaps that fronts engage the north west perimeters of the country with better 'success' than so far this summer?

We will watch and see how this unfolds anyway.

Hope this summer is also proving very much the type of thing that takes your fancy as much as my own. Keep enjoying it 

 

This isn't a first time I've said and done this, but no apologies once again for extracting sections from a post at the start of last week because all the main points discussed in that are now coming right under the radar of NWP

That suggested surge in atmospheric angular momentum tendency is duly underway. (Also notice when the last comparable leap occurred in mid April which presaged the first (of the many to come) warm downstream ridges of the season).

Its seemed like waiting quite a while for an expected bus in my own little weather world and happily getting my purse out of my bag in readiness to pay the fare as it appears around the corner 

Its equally good to see NWP models trying to solve the puzzle heading in week 2 of a trough replacing a long lasting ridge in the Atlantic and balancing the equation of how much downstream ridging occurs ahead of the trough. There are going to be mistakes for sure with this one and worth taking both operational and ensembles (inc clusters) with a bit of a pinch of salt for a while.

Whatever transitional flurry of more changeable conditions may come out of this, there is another lovely week (at leas ) to come and its seems unlikely our re-adjusting ridging is to be heading too far away. Also reasonable to suggest that jet stream distribution in the very extended period increasingly favours instability to focus to the SW (too much progressive push will probably be indicated to push eastward) and * just possibly* the hottest phase of this wonderful summer yet to come as a south easterly vector comes into play during the last third of July>into August

We will watch and see how it unfolds anyway.

Fingers crossed for our boys this week!

Keep enjoying it

 

[Fourty Point Three Degrees]

12z looking miles better than recent runs. Atlantic green snot kept well to the North. May this prolonged heatwave continue

[Mike Poole]

I see a shift in the GEFS ensembles on the 12z, here T240 on the mean chart , compared to similar but not exact time from the 6z:

Ridge not collapsing as some would like us to believe, I would suggest.

Edit: I've got to just pop this one in from the nether regions of the GEFS 12z mean, T312 the mean chart has >1020 over parts of the country, summer part two! 

Edited July 8, 2018 by Mike Poole

[Frosty.]

Really like the Gfs 12z operational, it prolongs this predominantly settled very warm / hot spell even further and shows high pressure building in again following a changeable blip! 

[Man With Beard]

My initial conclusion from the 12Zs is that any idea of a breakdown by the end of next weekend is dead in the water. Still looking like there may be a chance of a breakdown by 17/18th (on some outputs). Will it?