Model Output Discussions 12z 01/09/2016

[blizzard81]

The GFS 18z pub run holds out the prospect of maybe record cold for halloween :-o

[knocker]

Today and tomorrow brings quite a mixed bag of weather to many areas. This morning is quite foul in eastern Scotland and will probably remain so for a few hours whilst at the other end a band of rain will arrive in the south west later this morning and travel ENE. Tomorrow generally a showery day just about everywhere. Generally a little warmer than of late with the winds veering southerly.

The low to the west tracks north over the weekend and weakens but does establish a conduit to norther Canada down which the next trough travels effecting the UK on Tuesday before becoming a cut off upper low over Germany.

In the wake of the passage of this trough the pattern evolves thus, High Pressure builds from the south west surging north east over the UK whilst simultaneously a negatively tilted trough builds from Greenland running south east leaving this position and a feeling of deja vu.

So will the block prevail? The answer according to the GFS is no, just, but I think that best left for another day.

Edited October 15, 2016 by knocker

[knocker]

Just to note on the GEFS the continuation of the remarkable WAA into the Arctic.

[Frosty.]

The Gfs 00z shows an unsettled start to next week but by midweek we have high pressure building in over the uk which continues to migrate to the east and then really synoptically it's a repeat of what we have just had with a blocking scandi high holding the atlantic at bay so it's generally a rinse and repeat pattern for the most part.

Edited October 15, 2016 by Frosty.

[knocker]

The ecm pushes the trough through, just, next weekend. All very knife edge stuff

 

 

Edited October 15, 2016 by knocker

[Frosty.]

The Ecm 00z starts next week on an unsettled note but then our weather becomes largely fine but still with a risk of a few showers in the east but with sunny spells too and chilly nights with mist and fog patches forming where skies clear but then the uk becomes the battleground between the atlantic and the block to the east / northeast which would mean increasingly wet and breezy but mild or very mild conditions but still with some pleasant interludes in the e / se.

[SLEETY]

Still the impressive high latitude blocking continues even at the end of the ecm and gfs runs this morning,its fascinating to see what is going to evolve if this pattern continues to hold into November :-) :-) :-)

[Man With Beard]

The tendency is now to place a trough to our west/south-west at around D10. The northerly "signal" in FI isn't getting anywhere, and I suppose I should be suspicious of such signs, as they require the removal of a Scandi High that seems willing to build up with a sneeze at the moment.

The position of the trough lends itself more to a warm end of the month and a few ensembles go the whole hog and almost bring the 16C 850 line to the UK - on a strong continental path stretching to N Africa, that might result in a 23C/24C at this time of the year - of course, these are the extremes and the thread of such a warm push is so small that if you miss the centre it could be a lot colder, especially if the eastern block proves stronger yet again.

Nice to see WAA into the Arctic but I'd rather it was in 2/3 weeks time once there is a bit more bite in the vortex - too many times I've seen a blocked Autumn capitulate into zonality come December - does WAA at this time of year really affect the state of the vortex 6 weeks later?

 

[Summer Sun]

Low pressure stuck in the Atlantic and high pressure to the east = very wet conditions for some but milder at the same time

[carinthian]

All the main players going for a rise of pressure mid week over the UK linked to the Scandinavian High and a Upper Low circulation over Germany. Thereafter, it seems a battle of whether Tm or continental air mass wins out. The big models tending to go with the former with the west and north of the mild side and rather colder further to the Southeast, similar to the UKMO 5 to 10 forecast issued yesterday. The GEM looks like the colder option with some runs showing possible retrogression . The jury out on this one past 144 hours. Still great to watch how things pan out. Will look forward to UKMO updates later today. Here in the Alps our freezing level gone way back above the 2000 m this morning but snow portal services returns snow to low levels by Wednesday , thanks to a Upper Low circulation development over Germany.

 C

Edited October 15, 2016 by carinthian

[johnholmes]

The models continue to grapple with post tropical storms/hurricanes. This is mirrored in the normally less volatile anomaly charts. They remain inconsistent as they too try to work out where to place the main troughs and ridges.

links below

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

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

It will be a while I suspect before a more obvious pattern emerges.This is in the 6-14 day time frame not any further. In my view, shoot me down if you wish, November ideas and beyond should be in another thread! What happens in October has little or no bearing on the winter.

Attempts to link data over a short time scale to suggest something could happen have little statistical support. They could have if similar data over such short time periods were found in the past 100 years and they led to a particular weather pattern through the winter. Just my view of course.

[Grimers]

The GFS model and the ECMWF model show a low over W Ireland bringing light SW winds and mild temperatures to all parts of the UK tomorrow and a low NW of Northern Ireland bringing light W winds and cool temperatures to all parts of the UK on Monday.

       

Edited October 16, 2016 by Grimers

[Frosty.]

The GEFS 00z mean shows a prolonged largely settled / benign outlook once high pressure builds in around next midweek but still with a risk of a few showers affecting the e / se but it shows a generally pleasant spell with the block to the east strengthening and atlantic low pressure is held at bay. Temperature wise, next week looks close to average by day but with increasingly chilly nights with mist and fog patches but further ahead it becomes milder as we draw winds up from southern Europe and its only towards the end of october when we see lowering heights to the north with an increasingly n / s split and hints of widespread unsettled weather as we enter november but really it looks blocked for the foreseeable future across much or all of the uk.

Edited October 15, 2016 by Frosty.

[Frosty.]

Well the Gfs 6z is different, it still shows high pressure encroaching from the west next midweek with some fine pleasant weather with sunny spells after a rather unsettled first few days but there is a shallow trough across the low countries which starts to drift northwest into e / se the uk by the end of next week and at the same time, Atlantic low pressure breaks forward from the southwest and merges with the trough bringing an unsettled spell to the uk until eventually heights rise from the s / se and the jet becomes aligned sw / ne with a n / s split developing through low res with high pressure extending across the south bringing largely fine and very mild conditions with the north in the more changeable / unsettled atlantic regime.

Edited October 15, 2016 by Frosty.

[Frosty.]

An interesting end to the GEFS 6z mean and running through the perturbations shows some support for an Arctic plunge by the turn of the month..as has some previous output!

[Matthew.]

7 hours ago, johnholmes said:

 

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

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

It will be a while I suspect before a more obvious pattern emerges.This is in the 6-14 day time frame not any further. In my view, shoot me down if you wish, November ideas and beyond should be in another thread! What happens in October has little or no bearing on the winter.

Thanks for these links JH, really shows how forecasting anymore than 5 days at the moment is difficult because of TS influence. Surely a lot WAA into the Arctic in October could affect the SSW possibility for November + and therefore bring possible cold early winter if this happens? Only my simple logic though of what I've read.

Edited October 15, 2016 by Matthew Wilson

[Ali1977]

Much more blocking on this run at day 9

Day 10 is some of the most blocking I've seen on recent runs, cold Halloween incoming if this was true.

Edited October 15, 2016 by Ali1977

[Mucka]

14 minutes ago, Ali1977 said:

Much more blocking on this run at day 9

Day 10 is some of the most blocking I've seen on recent runs, cold Halloween incoming if this was true.

Yes perfect winter charts Ali.(in October)

This Op run has been repeated in the ensembles a fair bit but nice to see it operational output, albeit FI.

Retrogression to Greenland, nom nom nom. 

If only it were December... 

 

Getting a bit nippy in Central Eastern Europe,

Edited October 15, 2016 by Mucka

[Allseasons-Si]

OMFG!!!

 

[SMU]

spectacular GFS & GEM ( not to mention ECM was similar at 240 )

**IF** this varifies we are looking at a tanked -AO at around the 28th of October just days before the curtains raise for November AO stats...

the key period is 168- 216 getting enough greenland heights up against that low to reverse the 60N circultation-

goodbye zonal wind !

[knocker]

Of course the retrogression of the HP to Greenland could well allow the deep cut off low to the south west track north and open the door for a more zonal jet running to the south of the UK and thus more influence from the Atlantic in the medium term. Just a thought.

EDIT

But of course there is also the artic air running around the Hp as it continues to track west

 

Edited October 15, 2016 by knocker

[Mucka]

17 minutes ago, knocker said:

Of course the retrogression of the HP to Greenland could well allow the deep cut off low to the south west track north and open the door for a more zonal jet running to the south of the UK and thus more influence from the Atlantic in the medium term. Just a thought.

 

The jet is certainly running south of the UK Knock's, it is firing through Portugal and Spain.  ;P

The only Atlantic influence would be channel runners  (I know you meant medium term)

 

Obviously all in FI and I'd much prefer something like this later int he season but exciting output nonetheless.

Edited October 15, 2016 by Mucka

[knocker]

5 minutes ago, Mucka said:

The jet is certainly running south of the UK Knock's, it is firing through Portugal and Spain.  ;P

 

The only Atlantic influence would be channel runners  (I know you meant medium term)

 

 

O

Some influence

[Wilxy]

Some great WAA into the Arctic and Greenland, although I fear this is to early to have a impact as the vortex doesn't usually get going until the end of October.

[Captain Shortwave]

A few differences between the models around the day 6 mark but a general agreement on heights positioning to our north east again with a deep Atlantic trough developing.

GFS/UKMO/GEM

      

The UK keeps the high more UK based whilst the other two set up another easterly, though the UKMO solution would probably develop that easterly in a day or so.

Beyond this week then things get complicated as we deal with the interaction between the block to our north east and that Atlantic trough, the low over central Europe is again present like over the past week and will add an extra element to proceedings. I don't see anything particularly cool or warm in the coming 7-10 days, probably near normal, perhaps dropping a little below again if we see an easterly develop, but of course the interest lies in the future ramifications of this current blocking pattern.