Model Output Discussion 01/09/17

[johnholmes]

3 hours ago, ANYWEATHER said:

It won't happen there is a very high level of Shannon entropy or very uncertainty ,charts posted like that are merely for amusement 

amusement?

 I suppose it depends on whether you are a serious scientist or just a less knowledgeable bystander. 

 

[Man With Beard]

43 minutes ago, Frosty. said:

The Ecm 00z ensemble mean / like the operational shows high pressure in the ascendancy during next week with increasingly pleasant surface conditions developing, especially across the southern half of the uk with warm sunny spells and light winds followed by chilly nights where skies clear with mist / fog patches. 

ECM clusters show the detail behind that mean - not many options going against a longer build of heights in the direction of the UK, from D6 all the way out to D15. Likely to favour southern areas, but could spread to all.

Of course, at this time of the year, we start to lose the correlation between "high pressure" and "warm", so the amount of sun/warmth will depend a lot on the final position of the high. 

     

Unlikely to be too muddy for walkers for much of the first half of October, then.

[Polar Maritime]

Can we please stop bickering ☺ 

Some members post what particular charts are showing on each run, While others explain the variables and the most likely outcomes given the over-all data available. Just something to consider to save any confusion.

[Frosty.]

Longer term, the GEFS 6z mean looks encouraging with high pressure gradually becoming more influential, especially further south with increasingly calm settled conditions with pleasantly warm sunny spells and chilly nights with mist and fog.

Edited September 27, 2017 by Frosty.

[Frosty.]

The Gfs 12z shows high pressure building in next week after an unsettled start, it briefly gives way to allow more changeable weather before pressure rises again bringing increasingly pleasant conditions, especially further south with warm sunny spells followed by chilly nights with mist and fog and perhaps slight frosts..to me this run plays out like the latest met office update which longer term sounds good for the most part, at least across the southern half of the uk.

Edited September 27, 2017 by Frosty.

[Summer Sun]

Once the ex-hurricanes pass through UKMO shows pressure starting to build from the south-west which initially leaves us in a northwesterly flow

[The PIT]

Well the ex hurricanes seem to thrown a slight spanner in the works. So don't be surprised if the outlook changes somewhat.

[Frosty.]

The Ecm 12z shows an improving picture next week following an unsettled sunday and to a lesser extent monday, from midweek high pressure builds in nicely..warms up too..by the end of the run there is another surge of high pressure from the azores which would be very good news longer term..fingers crossed!

Edited September 27, 2017 by Frosty.

[knocker]

A quick look at this evening's ecm

After the Friday front and rain clears the fronts from the next low, situated about 500km west of Scotland by 1800 Saturday, are just impacting the west of Ireland. At the same tine ex tropical storms Maria and Lee are beginning to swing north east in the western Atlantic just south of the strong WSW jet which is even around 100kts at the 500mb level

The low and fronts then track east bringing heavy rain and strong  westerly wings Saturday evening and overnight into Sunday. Quite possible gales in western areas.  By 00 Monday the fronts are well clear and the UK is in a strong north westerly which could still give gales in Scotland.

By this time Lee has lost it's identity but Marie has latched onto the jet, just, in mid Atlantic and runs east then south east over Cornwall en route to France as it too loses it's identity.

From this point some amplification occurs with the main upper trough slipping south east into central Europe whilst the Azores ridges in the vicinity of the UK settling things down a tad by mid week after the hiatus of the weekend.

Edited September 27, 2017 by knocker

[Summer Sun]

An unsettled start to October but it might not last long with high pressure shown to return by mid next week

[Man With Beard]

3 minutes ago, Summer Sun said:

An unsettled start to October but it might not last long with high pressure shown to return by mid next week

Looks good for a traditional benign autumn spell. Small chance of dragging up some summery temps, but I'm thinking more about frosts.

Edited September 27, 2017 by Man With Beard

[knocker]

Firstly this morning a quick look at the outlook. ( just my take on it of course).

Last night’s NOAA, GEFS and EPS anomalies, whilst not in complete agreement, are in the same ball park enough to indicate that the pattern change hinted at recently is under way.

That means that the HP/trough axis with the negatively tilted trough in the eastern Atlantic has finally shifted east with the more traditional trough in the Greenland/Iceland area allowing the Azores to ridge in the vicinity of the UK.

Thus the upper flow should back south of west with temps returning to around average, As always in these situations the detail will be dependent on where the surface high cell resides but certainly a quieter and drier period for much of the UK is the percentage play with the north still in the firing of systems slipping around the top of the HP.

How long will this last?  The indications are not that long although there is no good agreement vis the ext period so suffice it to say we would appear to be looking at a traditional N/S split scenario with a trough to the NW and the Azores to the SW

On to the somewhat more pressing issues of the next few days.

Today there is currently a west/east split with rain still around eastern parts which should clear as the morning progresses whilst the west is quite dry and bright albeit a few morning mist patches. A deep Atlantic low will arrive west of Ireland later with associated front and this front will track east across the UK through Thursday evening and Friday bring rain to most places. Saturday should be a reasonable day but as can be seen on the 12 fax things are about to go rapidly downhill with the next low poised out west accompanied by ex tropical storms Lee and Maria. If you transpose the jet onto that chart it will be just to the north of them and from the WSW around 170kts

By 12 Sunday the low has tracked north east to be south of Iceland with the fronts over the UK bringing rain and strong winds, possibly gales in places, Lee has been absorbed in the general circulation so probably some tropical air in the mix. These fronts rapidly clear east but as the main low moves east the next front arrives (containing the remains of Maria) tracking south east overnight Sunday into Monday and this could well produce severe north westerly gales over Scotland in the early hours of Monday as the low is forced south east by the Azores surging to the west.

From this point the high pressure becomes the main influence with the odd system creeping around the top but best left around the ten day period. So certainly a quiet drier spell with temps around average is on the cards later next week

Edited September 28, 2017 by knocker

[knocker]

It goes without saying the ecm is at odds with the gfs from as early as late Sunday. It has the fronts sweeping through the UK Saturday evening through Sunday bringing heavy rain and possible severe gales in the west. They are into southern Norway by 06 Monday but it has the declining Maria tracking further north and it tracks it south east across England on Monday bringing heavy rain to England and Wales as it does so.

And it doesn't have the surging Azores high pressure post transit thus the rest of the week remains in a westerly unsettled regime with only the far south receiving any benefit from HP. and even that is tenuous. As is fairly obvious next week is still in the melting pot.

Edited September 28, 2017 by knocker

[Newberryone]

2 hours ago, knocker said:

It goes without saying the ecm is at odds with the gfs from as early as late Sunday. It has the fronts sweeping through the UK Saturday evening through Sunday bringing heavy rain and possible severe gales in the west. They are into southern Norway by 06 Monday but it has the declining Maria tracking further north and it tracks it south east across England on Monday bringing heavy rain to England and Wales as it does so.

And it doesn't have the surging Azores high pressure post transit thus the rest of the week remains in a westerly unsettled regime with only the far south receiving any benefit from HP. and even that is tenuous. As is fairly obvious next week is still in the melting pot.

Ecm may largely be at odds with the Gfs true enough, but there's no denying the end result, i.e day 10 chart is I'm sure you may agree, indicative of a more settled/benign period courtesy of that rise in pressure to the southwest. That little feature has the potential of becoming a blocking high I would think, thus deflecting systems well to the northwest for quite some time.

[JeffC]

7 minutes ago, Newberryone said:

Ecm may largely be at odds with the Gfs true enough, but there's no denying the end result, i.e day 10 chart is I'm sure you may agree, indicative of a more settled/benign period courtesy of that rise in pressure to the southwest. That little feature has the potential of becoming a blocking high I would think, thus deflecting systems well to the northwest for quite some time.

would that be a sort of a Bartlett High? If so better to get it done and dusted before it can work against us!

[Newberryone]

15 minutes ago, JeffC said:

would that be a sort of a Bartlett High? If so better to get it done and dusted before it can work against us!

At day 10 it's difficult to say owing to the fact the Ecm has a tendency to over amplify only to be more progressive again on subsequent runs. I hear what you're saying re a Bartlett High though, from being our summer friend to winter foe.

Edited September 28, 2017 by Newberryone

[karlos1983]

33 minutes ago, JeffC said:

would that be a sort of a Bartlett High? If so better to get it done and dusted before it can work against us!

Not really a Bartlett High, and I wouldn't want one of them in October, they can be a stubborn son of female dog to move. The so called "Bartlett" is usually centred to our south, not southwest,  as illustrated below. from my understanding anyway   *Not my graphics or text*

I'm quite happy to be corrected though.

[weirpig]

The first Mention of  a bartlett High this  season.    awaiting the mention of the 6z and 18z having  missing data.   the wheeling out of the Bom  when thinks get hairy   and the old quote that the met office hold the JMA in high regard.  yep its nearly winter.

[karyo]

13 minutes ago, karlos1983 said:

Not really a Bartlett High, and I wouldn't want one of them in October, they can be a stubborn son of female dog to move. The so called "Bartlett" is usually centred to our south, not southwest,  as illustrated below. from my understanding anyway   *Not my graphics or text*

I'm quite happy to be corrected though.

That's true but it doesn't take much for the Azores high to move a bit further east and nest there for quite a while.

[JeffC]

1 hour ago, karyo said:

That's true but it doesn't take much for the Azores high to move a bit further east and nest there for quite a while.

Can we re-name this set up Bartlett-ish then? - sorry OT I know!

Edited September 28, 2017 by JeffC

[Summer Sun]

A wet and windy start to October but it doesn't last long with high pressure quickly building as the low pulls away

[Frosty.]

The Gfs 12z shows high pressure building in next week with very pleasant conditions, particularly further south and east where temperatures climb into the high teens to possibly low 20's celsius which would be pretty good for early october but there would be some chilly nights where skies clear with mist and fog and perhaps slight frosts in rural areas.

[knocker]

Interesting this evening the gfs takes a decaying Maria Sunday at 06 and whips it north east on the very strong local jet in a bit of a squeeze and energizes it a tad on it's travels across Scotland and in the circulation of the main low

Edited September 28, 2017 by knocker

[knocker]

the ecm is still miles different to the gfs, even in the short time frame. After tonight It has the next frontal system crossing England and Wales on saturday whilst Lee loses it's identity. In the meantime the main low is tracking ENE to be south of Iceland by 12 Sunday and it's associated fronts are impacting Scotland bringing heavy rain and possibly westerly gales, maybe severe for a time.

At this time Maria is starting to decay away to the west but it gets caught up in the strong low level winds in the southern flank of the main low, merges into a frontal feature, and runs rapidly east and crosses Wales and southern England on Monday dumping quite a lot of rain, albeit quickly through.

It seems a bit odd but none of this is as yet nailed down.

 

 

Edited September 28, 2017 by knocker

[damianslaw]

Alot of uncertainty at the moment in very short-term timescales, all courtesy of ex tropical storm systems Lee and Maria. Difficult to call where these will track, and therefore who sees the heaviest of the rain. It is all rather messy.

Into next week a ridge looks like developing and a cooler NW flow will envelop the country, before we see a more pronounced build of heights from the azores anchoring itself towards us. What happens thereafter again very uncertain, in my view I suspect there will be too much energy in the atlantic to allow any sustained settled spell, and the heights will be quickly squashed south wards with a westerly flow taking hold, but hoping we squeeze out a couple of dry sunny days with chilly nights and possible frost.

All rather normal service for early October. Temps levelling out to near average.

Edited September 28, 2017 by damianslaw