Model Output Discussion - Autumn 2018

[BlueHedgehog074]

Probably as expected, not much change this morning, with a less unsettled spell this week still evident on the models. Mostly dry and bright with chilly nights likely at times, though a brief unsettled spell likely in the North mid-week as a disturbance tracks Eastwards over Northern U.K. Both the 00Z ECMWF and 00Z GEM seemingly the No. 1 models this morning for keeping pressure high around the U.K. area towards the ends of their runs. The GFS a little bit less so. 

(Would post charts, but on the way to work, so just a brief summary).

[Mike Poole]

It looks like this anticyclone will be with us for a while.  At T240 ECM has it slap bang over the UK:

GEM has it drifting to the east  bringing some warmth:

GFS on the other hand has it drifting to the west so cooler:

Pleasant enough either way.

[Frosty.]

Another cracking Ecm 00z ensemble mean in the longer term IF you love high pressure and very pleasant surface conditions..indeed, after today, it's anticyclonic throughout across central / southern uk!..enjoy☺

[johnholmes]

Using the anomaly charts this is what I wrote in my daily summation this morning.

Only ec shows any signal for troughing into Europe; all 3 show the main trough is way back, the Canadian main trough in fact. More settled more often for areas well south, less so the further nw one lives and probably mostly changeable covers it for the nw’ern areas of the uk.

Ec-gfs and ec not that different to the one above, less pronounced ridging though, gfs about the same perhaps?

Noaa and its ridge is less pronounced although the +ve signal looks very similar if slightly further w than that above.

links

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

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

Just one line of psters showing probably sums up how quickly any changes are likely.

No sign of an Indian Summer yet and no real signal for anything other than slight frosts under clear skies for the cold watchers.

Edited September 23, 2018 by johnholmes

[carinthian]

On ‎22‎/‎09‎/‎2018 at 08:53, carinthian said:

Morning all . looks like our team have got the track of the wave crossing on Sunday into Monday about spot on and that's a little bit further south as they had predicted ( re : above post ).The centre will cross central Europe and continue to deepen slightly but still move on at a pace and will produce some very strong winds, possibly damaging gusts, for a time behind the cold front after its passage, especially for the Northern Alps of Austria. Winds seems more of a problem than any temporary snowfall at altitude at this stage, Developments will be carefully watched over the next 24 hours.

 

Update, 60% chance of storms/Squalls to develop along the front heading towards Southern Germany and Northern Austria.

C

[Frosty.]

Looking at the GEFS 6z mean it's not just the short / medium term which looks generally anticyclonic.. it continues well into early october the further south you are..so...plenty of fine pleasant days to come with sunny spells and light winds but some cold nights with mist / fog patches where skies clear and even a risk of slight frosts in places, especially in rural areas..any occasional changeable / unsettled weather tending to be restricted to parts of northern britain (scotland) as atlantic conditions brush around the top of the high but for many of us BENIGN sums it up after today.

[Derecho]

Not much seems to have changed this morning, with the point of divergence being later on next weekend. A few cold northerlies are in there:

 Pretty cold but not anything out of the ordinary

For those who actually like stepping outside and make the most of the weather, there are plenty of good runs in there. Anticylclonic northerlies appear to be the slight favourite at the moment. Some rather pleasant days and some chillier nights.

 Not the warmest but plenty of good weather to be had

Some have the anticylclone to the east of the UK, this would lead to some warm weather. P7 is especially good and would lead to a prolonged warm spell. This appears to be a less likely option however.

   

Hopefully these runs come into fruition though, I think most people would like some useable summer before the winter sets in, can't see why anyone would complain about it. Bring on the snowy easterlies and northerlies later when they can count for something

Edited September 23, 2018 by Quicksilver1989

[Sky Full]

This is what I have been waiting for: cross model agreement on a six-day (minimum) settled, dry and quite sunny spell of lovely early autumn weather.  Out to +144 the prediction is unanimous:

UKMO:      ECM: 

GFS:         GEM: 

ECM and UKMO probably showing the best outcome for the whole country but GFS and GEM both promise settled conditions for most.

Even out at +192 the longer term outlook seems similar:

ECM:      GFS: 

GEM:  

If the ridge is allowed to drift eastwards a little we could see some quite warm temperatures as well but as things stand it's a cool but fairly quiet picture.  Excellent outlook for early October, in my opinion - it will allow the trees to colour up and lose their leaves naturally before the more active late autumn weather arrives.        There's plenty of work to do outside yet which requires dry weather.       And there's plenty of time yet for rain, cold and, dare I say it, extreme weather to show its hand - Christmas is still three months away yet!       

 

[Mike Poole]

Not much change on the 12s, GFS at T240:

Arguably the GEM is better positioned re the high to draw up some late season warmth:

I'm certainly not complaining about a settled couple of weeks with some warmth - I think this spell may include that last day we feel the heat of the sun before winter, as significant a day as the first frost at this time of year.

[ICE COLD]

Slight differences with the ECM tonight the high pulling out further west allowing colder 850s in from the north . Surely I'm not gonna get accused of spamming this thread up with this post am I ? 

[feb1991blizzard]

3 minutes ago, ICE COLD said:

Slight differences with the ECM tonight the high pulling out further west allowing colder 850s in from the north . Surely I'm not gonna get accused of spamming this thread up with this post am I ? 

 

 

Yes cold 850's, -6c in Scotland with -8c not far behind and the -12c isotherm nicely poised in the arctic rifle just in case the ridge is further west and sharper and rips into Greenland better than it is progged on that chart.

[Mike Poole]

Both the ECM and FV3 pull back the high pressure cell to the west allowing colder air early in the run, but at T240 on both runs it is swinging back the other way, with the high moving back over the UK:

The FV3 allows the warm air north better without that lower heights feature over France evident on ECM.  

[Frosty.]

Looking at the Ecm 12z, high pressure gets pushed and pulled this way and that and we get a cold crisp start to October which would feel quite wintry, especially further n / e...winter is coming!

[Mike Poole]

Sorry to be the harbinger of bad news: winter isn't about to start. ECM ensemble mean suggests a settled cool nights warm days regime at T240:

Actually looks settled through to the middle of October.  Winter can wait until SNOW is possible.

[East_England_Stormchaser91]

Latest ECM shows a potential hurricane or (medicane) forming south of Italy and then slamming Crete towards Rhodes. 

I have a friend holidaying in Kos later this week..! 

[Geordiesnow]

I think one thing to note is how the PV is going to get smashed up and by the end of September there is virtually no PV anywhere over the poles, disastorous conditions for the Arctic ice refreeze and Siberia is also looking very warm too so snowcover over Siberia could end up below normal indeed.

[ItNeverSnowsInWindsor]

Nice anticyclonic charts for October on the latest GFS 0z run with plenty of crisp cold mornings and sunny days

[Timmytour]

The amount of high pressure modelled to be on or around the UK for the next couple of weeks could be the catalyst for some spectacular autumn colours, especially when set against the background of a blue sky

[Weather-history]

That is dry away from the far north and even that is not that wet for autumn.  Out to 384

[mb018538]

25 minutes ago, Weather-history said:

That is dry away from the far north and even that is not that wet for autumn.  Out to 384

Indeed....nothing but high pressure on offer for the next 10-14 days at least you'd say. Partly helped by the cut off low down to the SW, which is just spinning away for the next week and keeping the high close to or over the UK. Thursday in particular could be very, very nice indeed with temperatures up to 22/23c, very respectable for the last week in September.

[SLEETY]

Some lovely weather on the cards for the foreseeable,but chilly nights.

No sign of a raging Atlantic yet,that can happen as we head towards October

The golf season continues  well in to Autumn this year Go Tiger

  And looking like great weather for Ryder Cup starting Friday .

[Jemma Croton]

Gorgeous outlook for the week ahead. Who doesn’t love a good anticyclonic set up? Blinding start to the season

[carinthian]

On ‎22‎/‎09‎/‎2018 at 08:53, carinthian said:

Morning all . looks like our team have got the track of the wave crossing on Sunday into Monday about spot on and that's a little bit further south as they had predicted ( re : above post ).The centre will cross central Europe and continue to deepen slightly but still move on at a pace and will produce some very strong winds, possibly damaging gusts, for a time behind the cold front after its passage, especially for the Northern Alps of Austria. Winds seems more of a problem than any temporary snowfall at altitude at this stage, Developments will be carefully watched over the next 24 hours.

 

Morning the squall line did cause some damage in parts of Germany but appears very localised. Now all Central Europe is in a much more seasonal air mass after weeks of abnormal heat. Indeed cold enough for snow falling on the mountain tops around Katschberg this morning. The forecast team this morning expect the weather to improve as the week progresses with temps around normal but have indicted in their model of quite a significant fall in pressure over the Central Med this coming weekend and may influence the position of of the large high pressure zone by then. Possible retrogressive movement of the high centre NW .If that's the case, could turn quite unsettled  in parts of mainland Europe but unlikely to affect the British Isles in the medium term, at least, but something of interest.

C

C

[Interitus]

2 hours ago, mb018538 said:

Indeed....nothing but high pressure on offer for the next 10-14 days at least you'd say. Partly helped by the cut off low down to the SW, which is just spinning away for the next week and keeping the high close to or over the UK. Thursday in particular could be very, very nice indeed with temperatures up to 22/23c, very respectable for the last week in September.

The active spell of weather that has just passed and the upcoming quieter spell can be seen quite well in terms of zonal available potential energy (ZAPE). The build up in ZAPE is related to temperature contrasts and a fall occurs with its conversion to kinetic energy through baroclinic processes in favourable regions eg north Atlantic - it is suggested that the largest fall in ZAPE occurred during the 'superstorm' of March 1993. The chart below shows the recent anomalous rise in energy available for extratropical storms -

The forecast shows that this surplus energy has now largely been expended leading to a quieter spell of weather for the NH extratropics in general -

(charts courtesy Jason Cordeira http://jasoncordeira.weebly.com/atmospheric-energy.html)

[carinthian]

Just from a personal observation, not sure how useful these charts are that far out at 360t. Two important facts that are possibly not taken into consideration by the predictive data are as follows :

I.  Wind data from the tropics to the equator is still very sparse even with advanced satellite technology ( this will in the future be an important research area )

2.. Temperature differentials between the North Pole and the equators continues to diminish ( this will have an affect on pressure patterns that will continue to evolve to a different scenario to the normal)

Maybe this NH pressure chart that far out will be spot on this time but likely to be corrected on a daily basis, so in effect no use to anyone that far out.

C