Model Output Discussions 12z 03/05/2016

[Man With Beard]

Summary of charts this morning: A decent weekend away from the north, cooler air with a weak front and showers progressing south Sunday/Monday, then a cooler airstream Tuesday till Thursday but mostly dry with just a few showers or minor troughs, most significantly on NW coasts I suspect. Then Thursday/Friday onwards for the rest of the runs, High Pressure is dominant over the UK, lots of calm, settled, sunny weather; temperatures recover to warm or possibly very warm, the only significant unsettled weather being for the far NW but they will join in with fine weather often. Good agreement between GFS/ECM/UKMO on these details.

[mountain shadow]

A UK centred high from the middle of next week then settled. ..Please make it so!

[Matthew.]

A Uk centred high would be a real joy..let's hope it comes to fruition we've waited since the beginning of June for this!

[stodge]

Morning all

Plenty to cheer fans of settled conditions, especially in the south, on the morning OP output. All the models are showing, after a brief hiatus early next week, an extended spell of anticyclonic conditions as the Azores HP moves in close to or over southern Britain.

I'd go for warm or very warm rather than hot based on what I'm seeing as the main airflow still comes off the Atlantic. GFS further into FI hints at the core of HP shifting north or north-east and that could import some hot air from the near continent but that's a very long way off and far from certain. It's also possible the HP regime will slowly relax back into the Atlantic as a more traditional North-South split takes over and retrogression isn't a completely lost cause either.

All that being said, it looks increasingly settled from the middle of next week onward, especially in the south but improving north and west with time. Warm or very warm by day but pleasant.

[phil nw.]

Yes the overnight ens are still trending towards a nice spell towards mid-month.

We can see on the gefs charts how gradually the jet starts to track further north compared to the near term.

Compare days 4/8/10

 

as last night's gefs showed,the Azores high extending ne and with time stretching across the UK towards Scandinvia.

The ECM mean is a promising chart too at day 10

hopefully this upbeat trend continues but the signs are there that the Icelandic trough shrinks north as the Azores high noses in quite strongly going in to the second week of the outputs.

 

[Man With Beard]

A very happy GEFS 00Z ensemble set too. 17 out of 21 members have no trough influence for the UK at all between D7 and D10. The other 4 can hardly be called unsettled either - the south stays pretty good on all 21 members. (I haven't posted the link as the whole set will change in an hour's time!)

[mountain shadow]

Very good 6z Op run with high pressure in control from the middle of next week until the end of the run, the only rain of any signifance away off in the Outer Hebridies as the jet is forced North East.

Could be a very very good end to the Summer across most of the country.

[Tamara]

 

Latest angular momentum budgets nicely underpin the shorter term modelling as last discussed on Sunday - but with further added interest. 

There is enhanced phase tropical forcing across the Western Pacific (MJO related) predicted in current models which adds westerly momentum to the planetary weather/climate system and if verified would further increase upward tendency in relative atmospheric angular momentum (to the base state) 

 

The strength of MJO waves impact on global weather patterns by interfering with the dominant ENSO base state and any eastward moving high amplitude tropical forcing will act 'destructively' on the on going cooling SST profiles across the Pacific

 .

Positive frictional torques are still sustained and continue to lead the way for mountain torques

This also supports the overall continuing trend of calculated momentum tendency (torque plus tropical forcing budgets) heading upwards - more especially any +ve mountain torque event which adds more atmospheric westerly momentum to the extra-tropical budget than +ve frictional torque.  Feedback lags from mountain torque events are up to 10 days - which underpins future amplification and height rises in modelling

These changing tropical and extra tropical elements need to be assessed against a total angular momentum budget that has been running through much of July and into August at between -1 and -1.5 SD - reflecting a modest low level global atmospheric angular momentum state (GLAAM)

Putting all this together, the signature expression of the Global Synoptic Dynamical model (the Global Wind Oscillation)  reflects the increasing momentum by heading from low AAM phases 1,2 and 3 back into Phase 4 once more

. 

Taking into account the +ve global torques and indicated increased tropical forcing both adding further westerly additions to the atmosphere, there are good grounds to see a rise in total angular momentum. GFS model suggests that the GWO has already moved into weak Phase 5 (high momentum state) before indicated orbit back to low Phase 8/0/1 signal. Usual disclaimer - don't take forecasts at face value. These are especially subject to changes day to day.

But could any higher AAM signal hold long enough to force a meaningful pattern change from the summer default?

It is a Nino like GWO Phase 5/6/7 orbit signal that holds the key to any holding high pressure synoptic in the further outlook period.    The summer so far has been prohibitive of UK/European upper ridge synoptics because of the atmospheric circulation being pre-disposed to a low angular momentum Nina type. This point has been stressed repeatedly in each post as a means to try and help manage expectations.

So I would still be cautious of drawing conclusions from face value intra day modelling. They will be highly sensitive to the balance of GSDM (GWO) modelling. Sustained upward tendency of AAM is required to push the total atmospheric circulation into a less Nina like signature. Until that happens, any modelling which tries to extend the Azores High north across the UK and Europe continues subject to some backward adjustment.

However, providing we see the predicted higher amplitude tropical forcing in the Western Pacific, then there is a reasonable chance of an anti-cyclonic spell - at least for a time and more especially further south and east.  No IMBY considerations at all here - simply a refection of how I think things stand.

Assuming tropical activity forecasts verify, an eye also needs to be kept on a sudden and immediate retreat from MJO Phase 6/7 as this will indicate that the SST processes in the Pacific which reflect potential Nina conditions establishing through the autumn are gaining ascendency through too much easterly wind additions to the atmosphere - despite the current indicated attempts of the atmosphere to add westerly inertia to it (and create eastward and northward propagated ridges).

Such a retreat and death of active tropical forcing will result in a fast reversal in any AAM spike - and accordingly any fine weather synoptics will revert to retrogression of the pattern back to a more withdrawn Atlantic Ridge and return of the Iceland/Scandinavian trough.

So for the balance of reasons and evidence given, I'm rather inclined for the time-being towards a half way house and wait to see how signals evolve further.

But for now at least, the medium term is looking a bit more promising than it has done recently

 

Edited August 5, 2016 by Tamara

[Man With Beard]

Umbrellas could feel rather lonely over the next two weeks if the 00z ECM is right

[BlueSkies_do_I_see]

These GFS +210 charts will warm the cockles of many Netweather users hearts.  For the first time in a long time, the jet stream seems to be heading north where it traditionally belongs in summer...

 

..leading to a big high centred over the UK.

Edited August 5, 2016 by BlueSkies_do_I_see

[I remember Atlantic 252]

same as above chart? dosen't look too nice here 18C, wind off the north sea, long way off yet though

[cheese]

28 minutes ago, I remember Atlantic 252 said:

same as above chart? dosen't look too nice here 18C, wind off the north sea, long way off yet though

If the wind was off the North Sea it'd probably be warmer in the west than the east.

[Frosty.]

The GEFS 12z mean shows an increasingly fantastic spell of summery weather once we get through the cooler blip early to mid next week. The Azores high becomes our Best friend, a friend who wants to stay through mid august and even longer! This would be most welcome in a misfiring summer so far with a nationwide increasingly warm & anticyclonic extended outlook..from what I've seen today, the future is looking very bright for the uk with hopefully the best of this summer still to come!

[markyo]

12 minutes ago, Karl. said:

The GEFS 12z mean shows an increasingly fantastic spell of summery weather once we get through the cooler blip early to mid next week. The Azores high becomes our Best friend, a friend who wants to stay through mid august and even longer! This would be most welcome in a misfiring summer so far with a nationwide increasingly warm & anticyclonic extended outlook..from what I've seen today, the future is looking very bright for the uk with hopefully the best of this summer still to come!

Pleasant weather for most,bit far out many of those to be taken to seriously but certainly pointers to where to look i feel.

[Frosty.]

Only the Best mean charts of the summer, hope this summer has saved the best until last...I'm starting to think it has!

[Frosty.]

Having said that, just seen the Gem 12z..wish I hadn't 

 

[Frosty.]

The Ecm 12z this evening shows no sign of a pattern change, just a typical north / south split with the south having some decent warm fine spells under ridging and the north, cooler and unsettled at times. The Gem 12z not buying a pattern change either anytime soon, just more of the same.

 

[Matthew.]

Thursday onwards below from the ECM 12z. This is very close to a long awaited settled spell. This could easily turn to something much more settled of course in future runs. Not a bad run in all respect

[Frosty.]

1 minute ago, Matthew Wilson said:

Thursday onwards below from the ECM 12z. This is very close to a long awaited settled spell. This could easily turn to something much more settled of course in future runs. Not a bad run in all respect

Disagree, it looks very ordinary, especially for the north where it stays unsettled..after the eye candy output earlier showing nationwide anticyclonic it's a crash back to earth from the ecm and especially the gem this evening. This Ecm run is nothing like as good as the 00z but that's not to say it won't be tomorrow.

[Matthew.]

4 minutes ago, Karl. said:

Disagree, it looks very ordinary, especially for the north where it stays unsettled..after the eye candy output earlier showing nationwide anticyclonic it's a crash back to earth from the ecm and especially the gem this evening. This Ecm run is nothing like as good as the 00z but that's not to say it won't be tomorrow.

I see where your coming from Frosty but yes definitely more runs needed let's hope for the 0z

 

[Frosty.]

On the plus side we have a terrific Gefs 12z mean longer term, you couldn't ask for better mean charts than those in a British late summer but the Gem 12z is a let down and to a lesser extent, the Ecm 12z which looks decent for the south beyond the cooler changeable blip next week but absolutely pants further north and isn't it about time we had a nationwide warm anticyclonic spell?..yes of course it is!

[Man With Beard]

Just now, Karl. said:

On the plus side we have a terrific Gefs 12z mean longer term, you couldn't ask for better mean charts than those in a British late summer but the Gem 12z is a let down and to a lesser extent, the Ecm 12z which looks decent for the south beyond the cooler changeable blip next week but absolutely pants further north and isn't it about time we had a nationwide warm anticyclonic spell?..yes of course it is!

It's a bit like the models have Rollerblades on right now? The ECM in particular has gone absolutely round the houses on the outcome for the end of next week, from Arctic northerly to continental southerly - absolutely massive pattern changes in just a few days. GFS has been much much more consistent - just hope it isn't consistently wrong! I think we need to wait a couple more days to see what kind of HP build we get into the UK. I can't quite believe the GEM and ECM can demolish a North Atlantic block so destructively that it doesn't even topple into a UK high, at least temporarily.

[Frosty.]

I completely glossed over the fact that this weekend looks very nice across most of England and Wales with a good deal of strong August sunshine and temps between 23/25c tomorrow, feeling very warm tomorrow due to light winds. Sunday looks much windier but temps still around 24c so no complaints further south..most of tomorrow looks pleasant further north before an unusually deep depression sweeps wet and windy weather across Scotland with westerly gales on sunday with sunshine and blustery showers across the w / n of scotland including the isles.

[Matthew.]

3 minutes ago, Karl. said:

I completely glossed over the fact that this weekend looks very nice across most of England and Wales with a good deal of strong August sunshine and temps between 23/25c tomorrow, feeling very warm tomorrow due to light winds. Sunday looks much windier but temps still around 24c so no complaints further south..most of tomorrow looks pleasant further north before an unusually deep depression sweeps wet and windy weather across Scotland with westerly gales on sunday with sunshine and blustery showers across the w / n of scotland including the isles.

Yes, just thinking the same myself. A great Saturday to look forward to

[johnholmes]

If you look at the 500mb pattern now and at 240h on the Extra link, you can see how it is predicted to change.

https://www.netweather.tv/secure/cgi-bin/premium.pl?action=gfs;sess=60060447a8a2d3a3d5d864616c095105

It is looking like this may be the pattern that devekops in the 6-10 day time scale as the synoptic idea fits the 500mb anomaly charts. So maybe we are about to have one of the short term ridging set ups that I think Tamara commented on?

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

The upper ridge and higher +ve 500mb heights being predicted seem to suggest the upper high and thus probably the surface high will be pretty much over the UK?

Even the 8-14 NOAA chart still has some indication of +ve heights in the UK area although no actual 500mb contour ridge over the UK

This is quite a change from the Atlantic ridge-Scandinavian trough upper pattern predicted up to 2 days or so ago.

Edited August 5, 2016 by johnholmes