Lucky to nighttime clouds overhead otherwise it would be cold.

Don't often post in this part of the web site but it seems that the models really are struggling with this stark divergence . . 

GFS 12z . . .

UKMO 12z . . .  

I wouldn't even bother posting if it is all in the 300 hr range, but both are in the 144 hrs range which I consider to be the outer edge of the reliable forecasting zone.

Let's see what the mighty ECM come up with this evening. 

High pressure still trying to cling on for as long as possible on this evening's GFS. It makes a big change from some recent runs and so time will tell if it's the beginning of a new signal. It's potentially looking very warm for the back end of September too, with some warm uppers over the country - I wouldn't be surprised if some favoured areas see 25°C under that.

Interestingly, the week after then turns very unsettled with the first cold plunge of the autumn into Scandinavia...

I've just added in a new feature which compares the Northern Hemisphere 500hPa profile for today with the same date in each year going back to 1948. An index is generated with a lower number indicating a better match.

The years are listed from best match to worst match. The index will update daily (hopefully from tomorrow if I've got the coding and scheduling right).

https://www.theweatheroutlook.com/premium/weather-analogues.aspx

Linked from the Model Inventory page here:

https://www.theweatheroutlook.com/twodata/model-inventory.aspx

I've just added in a new feature which compares the Northern Hemisphere 500hPa profile for today with the same date in each year going back to 1948. An index is generated with a lower number indicating a better match.

The years are listed from best match to worst match. The index will update daily (hopefully from tomorrow if I've got the coding and scheduling right).

https://www.theweatheroutlook.com/premium/weather-analogues.aspx

Linked from the Model Inventory page here:

https://www.theweatheroutlook.com/twodata/model-inventory.aspx

 

Intrguing. Is there a theoretical max or min value for the index number?

 

Intrguing. Is there a theoretical max or min value for the index number?

The theoretical min is 0! Not sure what the upper bound will be in practise, but early runs (I've done several updates on my development server) suggest 11,000 to 14,000.

 

The theoretical min is 0! Not sure what the upper bound will be in practise, but early runs (I've done several updates on my development server) suggest 11,000 to 14,000.

Presumably such an concept could be used to generate an index for cross-model agreement?

WX summary for UK much as yesterday though N Europe is warmer and drier (i.e. Wx summaries have a little warmth hanging on near the SW while N Europe is definitely cool. N Europe also getting the worst of any rain' the UK (except a wetter west coast) is less affected.)

Jet = more of a direct flow than yesterday's loops: Tue 21st across far north, moving S to Scottish borders Fri 24th, N England Thu 30th, weaker and forming al loop around UK Mon 4th

GFS - current trough slowly clearing E-ward and a warm HP cell established Wed 22nd SW England 1030mb but soon retreating to SW under influence of NW-lies from LP in Norwegian Sea. Pattern then becomes generally W-ly with deep LP Rockall 970mb Rockall Tue 28th, filling but throwing a trough across all UK Sat 2nd, in turn followed by a couple of weak LPs from the W across Scotland

GEFS temps much less certain than yesterday; fairly stable near norm to Thu 23rd (a burst of warmth in N before chaos sets in) after which a broad scatter 6 or 7 C boh above and below seasonal norm. A suggestion of colder early in the period esp in N. Not a lot of rain in E, rather more in W, distributed throughput.

ECM - differs from GFS after Wed 22nd, LPs coming further S; to N Sea 970mb Fri 24th and again Rockall 975 mb Sun 26th, the latter developing  a trough well S across England Tue28th

 

Presumably such an concept could be used to generate an index for cross-model agreement?

It could I suppose, but I'm not sure what the baseline would be.

I hope that high pressure continues to trend a little bit further north around mid-week. Wed/Thu have the potentially to be very warm days for the time of year. As of now it looks to be only the South and Midlands that will tap into it though.

I've just added in a new feature which compares the Northern Hemisphere 500hPa profile for today with the same date in each year going back to 1948. An index is generated with a lower number indicating a better match.

The years are listed from best match to worst match. The index will update daily (hopefully from tomorrow if I've got the coding and scheduling right).

https://www.theweatheroutlook.com/premium/weather-analogues.aspx

Linked from the Model Inventory page here:

https://www.theweatheroutlook.com/twodata/model-inventory.aspx

 

Are you archiving that list daily so an accumulated comparison over the autumn could be built up as to what are the closest matching autumns to the current?

Not much change in summary charts from yesterday - traces of warmth hanging on in the SW, most of any rain along W coast. Iceland and N Norway becoming notably cold in week 2

Jet showing a streak across n Britain Thu 23rd, moving N at first but the coming back as a loop from the S Tue 28th and doing a reload and repeat over the following week

GFS op shows trough over E coast moving away and then brief incursion of HP from SW Wed 22nd before collapsing to zonal pattern for a week, winds first from NW then SW. New LP develops to  Sw Thu 30th and is placed over Scotland 980mb Fri 1st and then another running N to he west of UK Mon 4th, maybe bringing some warmth from the S 

GEFS temps mostly above norm to Mon 27th (dip 24th) then less agreement but suggestion of a cool spell for 3 or 4 days, fairly dry in SE at first though damp in W, more rain everywhere after Thu 30th

ECM agrees with GFS at first though the lp thu 30th is only a shallow trough but does affext all UK

Interesting Tweet from Marco Petanga

https://twitter.com/Petagna/status/1439322652208943112?s=19

I wonder how this winter will pan out?!

Cold and snowy would be 😍

Looks significant,  could winter 21-22 be the 'Big One.'

Looks significant,  could winter 21-22 be the 'Big One.'

In an economic "Winter of Discontent" plus the end game of Covid it would certainly make it a memorable one, APS.

Roger

WX summaries implying a westerly typeof weather for the next 2 weeks - cool air spreading across Europe N of the Alps (really cold on Iceland & N Norway week 2) and rain on W coastal regions (Norway week 1, Britain week 2). The jet pattern mirrors this with strong flow to N of Scotland week 1, a brief spell with a loop around the UK Wed 29th, then a flow mainly across England interrupted by more loops.

GFS op - current trough moves away E-wards, HP from the SW for Wed 22nd, giving way to W-lies from controlling LP near Iceland until Thu 30th when new LP 975mb N Ireland moving slowly NW and filling over the next few days but leaving a shallow trough over the UK. Ex-hurricane near Newfoundland Wed 6th not at that stage affecting UK weather

GEFS - temps at or a bit above norm irregularly until Sun 26th, when more uncertainty sets in, but general trend is for cool weather lasting to Wed 6th (control run esp is pessimistic with several days ca 8C below norm, mean only 2 or 3 C below). Dry at first in SE, some rain there from Wed 29th, for Scotland  from Thu 22nd, not dramatic but no breaks in it.

ECM - that 'controlling LP near Iceland' is further to NW and pressure much higher over UK esp the S, so W-lies are present but weaker than shown on GFS. There is no new LP Thu 30th but pressure at that time rises near Iceland and falls in a broad band from E Atlantic to Baltic with no well-defined centre

Interesting Tweet from Marco Petanga

https://twitter.com/Petagna/status/1439322652208943112?s=19

I wonder how this winter will pan out?!

Cold and snowy would be 😍

Brian's analogue list currently has 1962 almost at the bottom, i.e. at this stage we are about as far from an analogue to that winter as we can get!

The GFS 6z going for a very warm start to October. 

https://www.wetterzentrale.de/en/topkarten.php?map=20&model=gfs&var=17&run=6&time=273&lid=OP&h=0&mv=0&tr=3#mapref

 ECM also very warm for this week. 850s significantly above average.  Wouldn't be surprised if we see 25c again this week.

https://www.meteociel.fr/cartes_obs/ecmwfens_display.php?x=315&y=143&run=0&type=0&runpara=0

 

 

Brian's analogue list currently has 1962 almost at the bottom, i.e. at this stage we are about as far from an analogue to that winter as we can get!

Screw 62/3, I'd be happy with an 81/2, an 09/10 or a 10/11.