Model Output Discussion - Into Autumn 2019.

[Methuselah]

GEFS 06Z ensembles are nae bad at all!

   

   

Still a tad worried about rainfall totals, though...We'll be able to see the rigs from Great Yarmouth next Spring: 

[knocker]

Without posting any other charts you can get a fair idea of the possible forthcoming evolution from these two

[Frosty.]

The Ecm 0z ensemble mean is looking predominantly anticylonic beyond the next few days with plenty of settled sunny and warm surface conditions to look forward to, especially further south where it could become very warm at times with temperatures into the mid 20's celsius and generally high teens to low 20's c for many but expect some cool / cold nights, especially where skies clear with a risk of mist / fog patches. The mean suggests a few less settled cooler interludes as the high changes position / orientation but for the most part it's smooth sailing into a prolonged quiet very pleasant outlook for the majority.....That's an amazing T+240 chart for a mean..exceptional!!

Edited September 10, 2019 by JON SNOW

[Don]

2 hours ago, weirpig said:

Why  are you making some correlation to the month of September?. 

It’s controversial but in the last 30 or so years, warm Septembers have tended to be followed by mild winters.  However, it could be argued this is just down to a warmer period!  If we look at September 1995, 2008 and 2017 to name a few, colder winters followed.  September 2009 was a little different being warmer and drier than average, but with a CET of 14.2C, it wasn’t well above.  The Weather Outlook also considers September weather patterns for their winter forecast. As I’ve said previously a cool/unsettled September by no means guarantees a cold winter, 2015 and last year are good examples of that!  However, I still believe a cool/unsettled September increases the chance of a colder winter.  On the other hand, warm/dry October’s, can increase the chance of a cold winter.

[knocker]

The frontal system associated with ex hurricane Dorian is already bringing rain to N. Ireland and south west Scotland The fronts, and rain, will track south east through this evening and overnight with some heavy pulses possible on the windward side of the mountainous areas of Scotland and north west England. The rain will tend to fragment somewhat in the early hours but showers will sweep in in the quite strong wind behind the cold front which will be lying across northern England

[MATTWOLVES 3]

1 hour ago, Don said:

It’s controversial but in the last 30 or so years, warm Septembers have tended to be followed by mild winters.  However, it could be argued this is just down to a warmer period!  If we look at September 1995, 2008 and 2017 to name a few, colder winters followed.  September 2009 was a little different being warmer and drier than average, but with a CET of 14.2C, it wasn’t well above.  The Weather Outlook also considers September weather patterns for their winter forecast. As I’ve said previously a cool/unsettled September by no means guarantees a cold winter, 2015 and last year are good examples of that!  However, I still believe a cool/unsettled September increases the chance of a colder winter.  On the other hand, warm/dry October’s, can increase the chance of a cold winter.

Its to controversial to even stress about Don. We are going through a period of relatively weak zonality at present, and have been for some time. Now if this holds firm through the coming winter, an SSW could bring alot of interest! Baring in mind how frequent these events are becoming.... So much to play for again this winter if you ask me. On to the here and now.... Its a beauty of a UKMO... High pressure well in control.... Keep those barbies on hold folks, that's providing you don't have them to late.

[Polar Maritime]

If we can please keep discussion to the Model output and away from Winter prospects in here please, Not only is it off topic but also far far to early to even consider given the Date. Thank you all and please continue.

[Frosty.]

The GEFS 12z mean indicates  high pressure (s) to bring a predominantly settled outlook beyond the next few days across most of the uk, the far north probably the exception where atlantic frontal systems could brush around the top of the high at times but for many, mid and indeed late september could look something like this..

 

[Methuselah]

This evening's GEFS 12Z ensembles maintain the mainly dry and settled theme, but temps look a little more up-and-down than was perhaps the case on some previous runs?

   

   

Nae too bad, anywho!?

[Frosty.]

The Ecm 12z operational is a peach, becoming high pressure dominated and very warm for the time of year, especially further south..could even be hot at times..perfick!!

Edited September 10, 2019 by JON SNOW

[knocker]

Merely an interesting observation considering the range but the ecm drives a trough around the eastern North American block which has profound implications downstream

[Lincs Observation]

reports today of a rare rapid increase in SSW in the Southern Hemisphere possibly leading to interesting weather later down the line. My question to those who know is what impacts would you expect further down the line for the Northern hemisphere (butterfly effect)?

LO

Edited September 10, 2019 by Lincs Observation

[shaky]

Unbelievable ecm mean this evening!!high parked right over the uk and actually intensifies in the latter time frames!!and i thought the op was a scorcher lol!!

[I remember Atlantic 252]

3 minutes ago, shaky said:

Unbelievable ecm mean this evening!!high parked right over the uk and actually intensifies in the latter time frames!!and i thought the op was a scorcher lol!!

that's why I class Sept as Summer, my model preferences just like in June/July, cold weather can stay away

[damianslaw]

Its September - so the inevitable slow moving high pressure must surely surface at some stage again - and going by today's models - yes once again it is about to move in.. how long will hang it around..

'wake me up when September ends'..

 

[Singularity]

 

The cut-off low remains an issue to resolve details-wise. GFS continues to make it a very clean affair, while ECM persists with a slight connection to the polar jet being maintained. 

The 850s from ECM for this day seem extraordinary for mid-September. Has the 17*C isotherm ever visited the UK this late in the year before? Maybe it did so even later, in 2011?

 

Further into next week, and GFS is still doing the same overall thing as the previous 12z from the model really - just with a trademark adjustment east (so many snowy winter northerlies lost this way...). Some distinctly fresh air still gets wrapped around to bring some cool nights and days falling short of the 20*C mark for most locations next Tue-Thu.

Meanwhile ECM continues to keep a weak chain of lower heights in play to the NW and N of the UK, preventing the ridge from building much north of the UK such that we're left basking in stagnating air of mostly tropical maritime air. Could potentially be some issues with low cloud or fog if you're seeking particularly high daytime temps, though.

 

Longer term, continued suggestions of a secondary surge of warmth somewhere in the range of 8-12 days from now by both models. September could prove to be one heck of a two-halves sort of month.

[knocker]

The North Atlantic 500mb and surface analysis for midnight

The cloud and rain associated with the warm sector will continue to slide away to the south east through this morning with the cold front clearing the south coast by early evening, resulting in an increasingly sunny day for most areas, Further north quite a few showers in the stiff westerly wind,

Any showers will quickly dissipate this evening leaving a clear night but ex TS Gabrielle, now a frontal wave, is tracking north east and will bring rain into N. Ireland, western Scotland and the far south west by dawn

The rain and quite strong winds will spread to much of the north and western regions through Thursday as the wave continues it's travels leaving much of the south east clear and quite warm but some rain will effect here later as the cold front clears to the south east.

This should be the last of any frontal systems traversing the country for a while as high pressure builds over the country. Thus a dry and sunny day on Friday but still some rain and a fair breeze in the far north from a stray occlusion

But over Friday night and through Saturday the upper trough in the western Atlantic deconstructs creating a cut off upper low and an intensifying surface low which tracks north east over Iceland. The frontal systems from this just impinge on the far north bringing strong winds and rain.

The low quickly clears away but leaves the cold front trailing across northern Scotland so still quite wet here on Sunday. Sunny elsewhere

Edited September 11, 2019 by knocker

[knocker]

According to the gfs over the 5-10 period further amplification of the subtropical high takes place over the UK as the trough in the western Atlantic edges east and the TPV consolidates over northern Russia. Ergo a lot of dry and sunny weather with temps a tad below average but this of course masks the marked diurnal variations that apply at this time of year with this analysis

[mb018538]

Still looking good for an extended run of settled weather. Temperatures varying as the high shifts position - warmest upcoming day looks to be Sunday at around 25c, before a few cooler days as the centre of the high edges out to the west.....before things potentially warm back up by Thursday as it starts to drift back across the UK and winds come up from the S/SE: 


 

[knocker]

Generally the ecm evolution is not dissimilar to the gfs but with some subtle differences, albeit nowt drastic

[shaky]

Amazing charts this morning again!!dry as far as the models can see and sunny and warm aswell!!a stronger high on the ecm for latter time frames aswell compared to the 12z run!!!

[knocker]

Just to note the ecm again tracks an upper trough around the East American block at the end of the run

Edited September 11, 2019 by knocker

[jules216]

I see a trend where deterministic output is way out of sync with its own ensembles for few days now in medium term(GFS), almost like 10C difference against ensemble mean for my location at day 7!. I believe it may be down to atmosphere - MJO waking up  and reacting to SSW in Southern Hemisphere which is being forecast now to emerge in phase 6 with reasonable amplitude. This MJO wave may help to wake up hurricane activity in Atlantic again and that could have downstram effect on amplifying the pattern upstream,but the energy is yet to be resolved weather it will lead to more eastward energy and flatting out Azores High or amplifying it even more  

[Methuselah]

Another decent GEFS 00Z ensemble, this morning: mostly warm, but never hot, afternoons and cool, misty/foggy nights and mornings. Nae bad for September.

   

   

There are of course some quite nippy days in there, too!

 

[Seasonality]

34 minutes ago, jules216 said:

I see a trend where deterministic output is way out of sync with its own ensembles for few days now in medium term(GFS), almost like 10C difference against ensemble mean for my location at day 7!. I believe it may be down to atmosphere - MJO waking up  and reacting to SSW in Southern Hemisphere which is being forecast now to emerge in phase 6 with reasonable amplitude. This MJO wave may help to wake up hurricane activity in Atlantic again and that could have downstram effect on amplifying the pattern upstream,but the energy is yet to be resolved weather it will lead to more eastward energy and flatting out Azores High or amplifying it even more  

I agree, there is an exceptional event taking place in the southern hemisphere and it will be fascinating to see how it plays out for us on the other side of the world.