Model Output Discussion 18z 28/07/13

[Summer Sun]

The latest met office update to September 10th points to a north south split from mid next week

 

Northern areas are likely to remain rather changeable and windy, with showers or perhaps longer outbreaks of rain interspersed with brighter periods and generally near normal temperatures. In the south, some rain or showers are likely, but here there is likely to be more in the way of dry and sunny spells, turning warm at times.

 

With the warmth and clear sky by day the south could see some chilly nights with fog possible in some spots as well

 

Longer term from GFS and we see the blocking high return

 

 

Temperatures look to be around the mid 20's in the south high teens to low 20's further north though its shown to turn warmer still towards the end UK wide (add around 3c on for the afternoon peak)

 

[bluearmy]

Despite generally reasonable ens mean output and extended naefs weak positive anomolys, the spreads on both ecm and neafs reveal a propensity to bring the depressions influence further south on a west/east axis. If this clustering verifies to any extent,, we could be seeing some early autumn gales in the north of the uk, come the latter part of next week and beyond. That energy over ne canada is spurting out some low height lows although as we head through week 2, it may well become less influencial as it fills somewhat and heights rise.

having seen the way the weekend low is likely to influence our weather and the apparent surprising introduction of further depressions into the latter output i would urge some of you to view the spreads on meteociel (click 'ecart ') to get a feel for how solid the ens mean is. It also shows any strong clustering for an individual feature, be it ridge or depression, against the mean. Remember, the stats show that the mean verfies higher than the op post day 4/5. Thats the general lw pattern. Finding the features within the flow is the secret thereafter.

Edited August 27, 2013 by bluearmy

[AWD]

We are now entering the time of year when big tropical storms and hurricanes can cause large swings in NWP output, more so than usual. Operational output into the medium and long range will show large swings in projections and will really be hard to use for any realistic forecasting means.

Although ensemble products won't be immune from this, there should be better stabilisation in ensemble and anomaly products than operational products. Take all operational output, regardless of what it shows with a sensible amount of sceptism at this time of year especially.

To add my two pennies worth then, after what looks like a cool weekend coming up, with showers and spells of rain and wind in the north, and less so, if any further south, the path into next week is looking split.

The MJO, whilst still on the weak side, as gained some sort of life now with all 3 main models suggesting a move into and around phase 1. The ECMWF most progressive of the 3, with hints of a phase 2 outcome in the longer term;

Both phases conclude to something typical of a UK early Autumn pattern. The more unsettled and windy weather always in the north, whilst the south sees more in the way of drier and calmer weather.

The ECMWF 0z mean for mid next week showing this north/south split perfectly IMO, both pressure wise;

And 850hpa temperature wise;

A look at the spread next week shows little chance of any high pressure to our east/north east, resulting in any significant heat a few GFS FI Op runs were showing recently, with much lower pressure over Scotland and Scandinavia;

This scenario will result in winds of a westerly quarter off the Atlantic, sometimes north of west, especially in the north of the UK as low pressure systems push west - east across the GIN corridor;

This also highlighting the north/south split in temperatures. The south seeing temperatures around average, sometimes a tad higher than average. The north seeing frequent spells of cooler than average temperatures as the pressure systems bring some early Autumn rPm air down on their western flank. Again, a typical early Autumn pattern.

The latest GEFS for London show the 850hpa temperatures spreads to be around average, perhaps just favouring very very slightly above mean values;

And with SLP never really dropping too low, rainfall always looks minimal, with what does fall looking more like showery rain rather than frontal rainfall;

So a north/south split looking favourable next week IMO. Some pleasent, useable outdoor weather for the south with temperatures never far away from average values most of the time, perhaps a tad above too. Fresher in the north, with some windy weather likely at times. No washout likely here either, but something resembling more Autumnal conditions is looking possible.

Edited August 27, 2013 by AWD

[mushymanrob]

the 3 anomaly charts have not been totally consistent either with themselves or each other but the overall pattern has stayed the same, +ve height anomalies west or WSW of the UK and a mainly W'ly flow across the Atlantic into the UK. The idea of a ridge has never really been a major feature if you watch these things daily and take an overall view of what they show.

 understood... i was thinking that when something emerges, maybe one of the three picks it up before the others? only for the others to fall in line?..

[basfordlad]

As a newbie, having looked at these charts, i am trying to work out the weather for next week.

 

Been quite interested in the weather since early spring, useful when you have an allotment!

 

Now the question is , what is the weather likely to be for next week in Southern Scotland, looking at Gavs Weather vids and the weather outlook it suggest it might be quite changeable, 

 

So if people think its going to be quite changeable, i am thinking we might have to head to the south Coast instead. boo hoo!

[draztik]

GFS 12z seems to be reverting back to its original course, before it moved inline with the ECM.

this would allow pressure to rise more considerably, than what was shown on the 6z.

12z on the left, 6z on right... Big change!

Edited August 27, 2013 by draztik

[No Balls Like Snow Balls]

GFS 12z seems to be reverting back to its original course, before it moved inline with the ECM.

this would allow pressure to rise more considerably, than what was shown on the 6z.

 

 

Yep it takes the low back on a NEasterly track. UKMO seems to be following similar lines to. Plenty of chopping and changing in regards to placement of the low at the moment.

[Summer Sun]

GFS 12z seems to be reverting back to its original course, before it moved inline with the ECM.

this would allow pressure to rise more considerably, than what was shown on the 6z.

 

Indeed the low is further north now so other than cooler temperatures the weekend would be fairly quiet

 

 

Milder air will start to move back in on Monday

 

Edited August 27, 2013 by Summer Sun

[shaky]

Big change on the gfs 12z!!high pressure back in charge!!get in there!!hopefully ukmo 12z will be the same!!

Edit:12z ukmo brings high pressure back in charge aswell!!thank god!!the low pressure can just sod off in my opinion!!

Edited August 27, 2013 by shaky

[Summer Sun]

UKMO has the high coming back in on Sunday now by Monday its a north south split

 

 

Later next week GFS introduces something more unsettled

 

 

 

It might also be worth keeping an eye on the low in the Atlantic at this stage its heading to the UK

 

Edited August 27, 2013 by Summer Sun

[draztik]

Summer sun, that low you mention also appears on the EPS control, tho it had brought it much quicker, by the weekend of the 7th. Tho being so far away, it will no doubt change trajectory.

Edited August 27, 2013 by draztik

[Methuselah]

Never mind guys, I'm sure that none of those outputs will be right...

 

A genuine question: if the CFS is useful tool 'when read correctly', why haven't seasonal forecasts noticeably improved since its inception? 

Edited August 27, 2013 by A Boy Named Sue

[basfordlad]

So does this change mean scotland won't get it so bad?

[East_England_Stormchaser91]

Lol, tropical storm incoming to the UK at 300+hrs according to the reliable FI 

[Summer Sun]

ECM continues to keep the low away from the UK for Saturday even the far north of Scotland keeps pressure above 1000mb

 

 

Fresher air is also making its way from the NW

 

[shaky]

Yes yes!!!!!!now its the ecm which pushes that low out of the way for the weekend!!and a good pressure rise to follow!!long may this sunny weather continue!!muhahahha!!'

[Captain Shortwave]

Uppers of 10C across the whole of the UK by day 6

Just depends how much sunshine we get to see how high the temperatures would get.

[Summer Sun]

Sunday has gone from looking unsettled a few days back to settled now with high pressure pushing northwards again

 

 

Monday the high is back in place

 

 

By t168 the high looks slightly further north when compared to this morning

 

Edited August 27, 2013 by Summer Sun

[Milhouse]

It does seem like all 3 models have flattened next weeks high a bit compared to a couple of days ago with the GEFS mean not so confident of a widespread rise in pressure. But at the moment all the big 3 models agree on a return to the warmth for southern Britain after average or slightly below average temperatures on Sunday. There will be more changes to come with regards to prospects for early next week. The high could build further north than is currently being suggested or it could be pushed further south by low pressure resulting in a more w/nw flow.

The ECM currently has high pressure drifting off into Europe early next week and low pressure centred roughly over Iceland well away from the UK. This would result in some very warm conditions for the UK especially central and eastern parts.

 

[Joe8987]

Every time I visit this thread we seem to be on the verge of another heat wave/hot spell. Not one has materialised...

[Summer Sun]

By Wednesday the high is clinging on for the south which is where the warmest conditions would be found

 

 

By Thursday the low breaks through introducing fresher air for all

 

[draztik]

the ecm 12z @ 240

dang!!!

[Captain Shortwave]

Good thing this is only at T240 and likely to be rather wrong

 

  

[Man With Beard]

I sense a change coming the weekend after next, this isn't the first time such a chart has appeared:

 

 

 

This would be followed with showers, a chilly wind and high teens for most, maybe less in the far north.

 

Till then, on with the south-coast h*****ve for me I think! It's been stunning here the last 9 out of 10 days (joe8987, apologies, you obviously don't live round here) and I can see the next 7 days going the same way judging by tonight's ops, perhaps a very very short blip on Saturday

Edited August 27, 2013 by rjbw

[East_England_Stormchaser91]

Every time I visit this thread we seem to be on the verge of another heat wave/hot spell. Not one has materialised...

Hmm, was I in the same country as you throughout all of July and early August?