Model Output Discussions 12z 01/09/2016

[damianslaw]

Not often you can say the models are in agreement throughout all timeframes - at least 240 hrs! - rare indeed. We have a classic azores high ridging through the country and into scandi scenario, with the jet tracking far to the NW sending frontal activity away from our shores. What we are left with is a full blown easterly flow, off a still warm continent. How warm things become next week is open to question, much will depend on how sunny the airstream is expected to be, but it does look like many will see very respectable temps for early October, though nights could be quite chilly.

Looking further ahead, ECM is showing a classic retrogression pattern, the next timeframe would show heights building through up to Greenland, this often does occur when heights become very strong - as they are forecast to do.

Gosh if this was winter, this thread would be crashing... alas we are still just on the right side of the year for easterlies to deliver warmth still, if this was a month ahead we would be looking at a colder than normal period, with a rapidly much colder continent.

(BBC will have to do a marked u-turn this evening in their long range forecast, yesterday they were saying westerlies would dominate with the jet crashing through - tonight's should be showing the complete opposite - I did wonder yesterday what charts they were looking at, as it was clear the models were not showing such a thing at all).

[mb018538]

I wondered this too....I didn't see anything yesterday pointing to an Atlantic dominated period after early next week!

[Neilsouth]

Why the excitement? Easterly winds = cold, possibly cloudy weather coming in off the north sea for many eastern areas. 

[Frosty.]

2 minutes ago, Neilsouth said:

Why the excitement? Easterly winds = cold, possibly cloudy weather coming in off the north sea for many eastern areas. 

Actually the winds next week look more SEly from the warm near continent with plenty of sunshine too.

[Neilsouth]

3 minutes ago, Frosty. said:

Actually the winds next week look more SEly from the warm near continent with plenty of sunshine too.

Hopefully! South East winds are nice

[Mark wheeler]

Hi , the metoffice office updated seasonal forcast that has been mentioned I have been searching but I can't seem to find it can any one point me in the right direction please. Great looking charts tonight .

[Daniel*]

19 minutes ago, Mark wheeler said:

Hi , the metoffice office updated seasonal forcast that has been mentioned I have been searching but I can't seem to find it can any one point me in the right direction please. Great looking charts tonight .

Here you go: http://www.metoffice.gov.uk/media/pdf/1/p/Forecast-temp-OND-v1.pdf

 

[Frosty.]

41 minutes ago, Mark wheeler said:

Great looking charts tonight .

I couldn't agree more, the Euro 12z (ukmo / ecm) outlook is as good as it gets for the first full week of october, hopefully the models will continue to firm up on this!

Edited September 29, 2016 by Frosty.

[damianslaw]

Worth a look at the jetstream forecast profile, it can't be relied on like all long range model predictions, but interesting to note it is showing a split jet next week, with energy going into the southern arm, which would back up the ECM and GFS hint that heights instead of collapsing south into Europe, will instead retrogress NW to languish somewhere to our north instead, the cut off low feature over Europe thus being an important feature in enabling this to happen.

 

[blizzard81]

7 minutes ago, damianslaw said:

Worth a look at the jetstream forecast profile, it can't be relied on like all long range model predictions, but interesting to note it is showing a split jet next week, with energy going into the southern arm, which would back up the ECM and GFS hint that heights instead of collapsing south into Europe, will instead retrogress NW to languish somewhere to our north instead, the cut off low feature over Europe thus being an important feature in enabling this to happen.

 

I guess you are mentioning this with a view to how this upcoming winter will pan out - hopefully? Otherwise, way too early for retrogression for my liking.

[knocker]

Except that that isn't the evolution the EPS is suggesting. In the ext period it continues what it starts here and has he LP to the SE, the Scandinavian HP drifting east, and a suggestion of the Azores ridgng before the upper flow veers WSW.

I wouldn't think NOAA is a million miles away from this.

 

Edited September 29, 2016 by knocker

[Daniel*]

What a dreamy evolution GFS jumps on board with ECM, but does one further , what seems clear to me is we're in a different ballroom, to last year, we're in tune to something more favourable? 

Robust block to NE retregressing to Greenland linking with that ridge bingo. Netweather servers would have combusted if such occurred a month later - the type of evolution that occurs extremely infrequently, however it may not have much substance ,I think October could end up becoming rather chilly feeling. After a warm start, watch this space. Quite a strongly pronounced -AO being signalled into the second week of October, and perhaps coupled with a going negative NAO by mid month, our buddy the PV will be disturbed I'm rather certain on that, I have an incline winter could start early - early days and all that, but interesting to see apart from if you're knocks maybe, roll on the funny season, I think the seed has germinated.  

Edited September 29, 2016 by Changing Skies.

[knocker]

Today

Sunshine and showers.

The GFS this morning

A shallow low traverses the country Saturday bringing frequent showers to many areas followed by a drier and quieter Sunday. Then the expected amplification with pressure building to the east and a deep trough mid Atlantic finds a deep surface low moving north into Iceland with fronts stalling over Ireland and only effecting Scotland on Tuesday.

This remains the pattern for the next two or three days with the UK in a slack SE airstream and only NW Scotland and N' Ireland effected by Atlantic systems. But by the weekend the high pressure to the east is moving east allowing the Atlantic a foothold and the Azores to ridge creating once again a N/S split before the floodgates open, but that will keep.

Edited September 30, 2016 by knocker

[mb018538]

We also have hurricane Matthew to contend with - it looks like curving back up along the eastern seaboard through next week, and this will undoubtedly play havoc with the atmosphere. I'd say up to the middle of next week looks fairly nailed on, but after then all manner of options could happen. One to keep tabs on:

[bluearmy]

Quick look a the 46 day ECM and early november begins to show the higher heights anomolys across to our north with some lower ones to our south. A long way off and a mean at 40 days + but something to build on in conjunction with the met office contingency planners wording. 

 

Liking the the way the gfs op in fi drops the trough through Western Europe - diving troughs deliver coldie winters.  means nowt given its  fi gfs but at least it isn't a blow torch scenario!  If it verified then could be a pattern to build on going forward.

[knocker]

The ecm has a not dissimilar evolution as the GFS next week, perhaps hanging on to eastern HP a tad longer before it moves east, and then a favourite with the ecm,  some trough disruption and a cut off upper low to the SW. producing a very complicated surface analysis for the end of the run. Best file this. Off for a chat with Sidney.

Edited September 30, 2016 by knocker

[mb018538]

ECM this morning shows high pressure dominating the scene, with low pressure well out of the way towards Iceland. Ex-Hurricane Matthew appears at 240 as a nasty low near Newfoundland - and will undoubtedly have an effect on patterns thereafter.

[knocker]

The EPS still indicating the beginning of a return to zonal towards the end of next week with the Azores ridging into the south but still retaining temps a little above average for a time. As we move into the ext. period the trough becomes more active and we are in familiar territory of LP to the NW and HP to the SW and the proverbial N/S split with temps around average.

Edited September 30, 2016 by knocker

[Man With Beard]

So this morning's runs, on the whole, dropping the idea of a medium-fetch easterly - the flow remains on the southern side of east and consequently temperatures probably won't drop much in the first third of October - maxes of 20C odd likely on many days.

However, this is an interesting GEFS mean chart at D12 and is fairly representative of the clusters:

We have a trough diving through the UK, with Azores High slightly displaced west (almost all ensemble members agree with this) and a semblance of heights to the east. The eastern heights is what the ensembles disagree madly over. There's a sizeable cluster (50% of the whole suite) that build heights back westwards over the top of the diving trough. This is one of the more dramatic ones:

Now this particular member isn't as cold as it might look as Mediterranean air gets in from the SE, but the ensemble diagrams show how much cooler it might get

which would produce temperatures in the low 10sC rather than low 20sC as mid-month approaches.

Not that this is a huge anomaly for the time of year, but a huge change from the mild autumns we've been used to!

Personally, I think the pattern is going this way. Heights to the NE keep going strong, and a diving trough through the UK is bound to encourage some sort of build of heights in the direction of Iceland.

 

Edited September 30, 2016 by Man With Beard

[Matthew.]

Yes agree with the potential of a change Man with Beard. Longer term things could get very much cooler if this pattern develops from mid month. I always think its a good sign for cold lovers if systems  start moving Nw-Se from mid October+

In the shorter term if the Anticyclone draws in a Se instead of E then some very pleasant sunny days and misty mornings could be on the cards

Edited September 30, 2016 by Matthew Wilson

[MR EXTREMES]

sods law we get easterly now watch be sw flow for november 

be interesting to see how long this scandi heights hangs around 09/10 had heights which were really hard to breakdown.

starts warm but looks likely to cool of with some cloudy weather for east or southeast.

[feb1991blizzard]

Snow for the Scottish highlands.

[MR EXTREMES]

gem is a mid winter GEM

[Man With Beard]

And here is the problem with forecasting a diving trough - on the GFS 12Z this evening, the trough goes a little SW and develops its own circulation, resulting in a warm draw from the med. But 500 miles north-east on the pattern and we'd be cold under the trough - 500 miles south and we'd be in a slack easterly flow with risk of fog and frost. It demonstrates how the diving trough scenario is a complete wildcard so far out, even though lots of ensembles are picking it up.

[Matthew.]

The ECM shows a cold outcome next Sunday. If it was winter rain might be turning to snow as pressure grows in the mid-Atlantic

Edited September 30, 2016 by Matthew Wilson