Model Output Discussion - Into Autumn 2020.

[Cheshire Freeze]

All going perfectly. If there's one pattern I want to see set up in late Oct into Nov it's an unsettled S'ly episode. LP not making it much past the meridian against blocking further E is a key indicator of a disturbed trop further into Nov-Dec.

Far from a traditional zonal jet-

Edited October 15, 2020 by CreweCold

[Griff]

18 minutes ago, CreweCold said:

All going perfectly. If there's one pattern I want to see set up in late Oct into Nov it's an unsettled S'ly episode. LP not making it much past the meridian against blocking further E is a key indicator of a disturbed trop further into Nov-Dec.

Far from a traditional zonal jet-

This is good to hear, a couple of signs on social media that some winter cold fans are getting... 'cold feet' (sorry) regarding the return to +NAO. 

[Cheshire Freeze]

5 minutes ago, Griff said:

This is good to hear, a couple of signs on social media that some winter cold fans are getting... 'cold feet' (sorry) regarding the return to +NAO. 

You'll always get a period of trop vortex intensification before any break up, it's this that essentially does the damage, providing we get blocking signatures in the right place. 

Look at the archives and you'll see that any -AO rarely lasts all the way through from autumn into winter cold spells.

We're looking at mid-late Nov for the next period of 'interest'. Hopefully bringing our first snowfalls.

Edited October 15, 2020 by CreweCold

[Frosty.]

I was rather hoping the GFS / GEFS would have built on the idea of the 0z op with a risk of a good dump of snaw for parts of Scotland early next week but that seems to have diminished considerably, it would certainly have spiced things up next week talking about snaw in October!!!!..and who knows, with some uncertainty about exact low pressure tracks..perhaps we won’t be only discussing mild, wet and windy!!!!...anyway, whatever transpires, winter is edging closer and will hopefully be a vast improvement on recent ones!!!!!! 

 

[ICE COLD]

41 minutes ago, CreweCold said:

All going perfectly. If there's one pattern I want to see set up in late Oct into Nov it's an unsettled S'ly episode. LP not making it much past the meridian against blocking further E is a key indicator of a disturbed trop further into Nov-Dec.

Far from a traditional zonal jet-

Your getting me quite excited about the upcoming winter Crewe . You seem quite positive that we’re gonna get a half decent winter ? Hope your right . It’s the most positive I’ve seen you

[mb018538]

I see it the other way - AO and NAO snapping back sharp positive, and PV really picking up towards the end of the month. Let’s hope it’s not just a precursor to our usual filth we have to endure.

[Penicuikblizzard]

Just now, mb018538 said:

I see it the other way - AO and NAO snapping back sharp positive, and PV really picking up towards the end of the month. Let’s hope it’s not just a precursor to our usual filth we have to endure.

It happened last year early November was fairly cold with snow down to low levels in parts of Scotland with winds from the NE,,, then it all changed the PV ramped up and it was mild from Dec through to Feb, can see the same thing happening this year too.

[Griff]

6 minutes ago, mb018538 said:

I see it the other way - AO and NAO snapping back sharp positive, and PV really picking up towards the end of the month. Let’s hope it’s not just a precursor to our usual filth we have to endure.

Petanga 'twitted' (sorry) a reply to me earlier suggesting I keep an eye on the latest met office 6-30 days forecast. 

Their modelling suggests a return to colder conditions after a more familiar period of +NAO... Pretty much as @CreweCold was alluding to, all be it in the shorter term at least. 

[Jason M]

PV will soon get going through late Nov / Dec. The correlation between a weak PV in October and what happens over the Winter months seems low to me. As always the question is can we squeeze a disruption to get a decent cold spell at some point over the DJF period? The answer as always is probably 'no', but with the small chance we might get lucky. 

[Frosty.]

Honestly guys, I am a coldie despite what some may think of some of my recent posts but I’ve just checked the longer term GEFS 12z mean and it shows this!!!

Anyway..the hunt for cold goes on and on but fear not, winter is still six weeks away!

[mb018538]

Quiet now for the next 3 days as high pressure take charge of our weather. Enjoy this calm spell, as the wind and rain returns for all next week!

Western areas more at risk of seeing the heaviest rain, but even the driest spots in the east seeing 35mm plus in the next 10 days, with 75-100mm possible over western hills.

Going on this mornings ECM/GFS, next week shows milder air dominating more than colder air especially in the SE, where 18-19c is possible in the SE on Wednesday. Scotland and parts of the NW looks pretty chilly throughout:



 

[johnholmes]

Friday 16 October 500 mb update

All 3 look fairly similar with n America and on into Europe with the major trough-ridges in similar positions, with 2 out of the  3 giving a fairly slack S of W flow into the UK with trough to the west the main feature. Noaa is rather different in its treatment of this trough. But overall the flow looks to be probably much as Noaa shows in the 6-10 period, its 8-14 has the troughing, just W of the UK into Iberia rather sharper than the 6-10. The flow on this is diffluent so possibly some deepish developments as surface features come across the Atlantic deepening in that area just mentioned? Likely also becoming on the mild side at times, and windy as deepish lows affect the country from time to time along with spells of rain, more showery behind the attached cold fronts for a time.

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

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

Edited October 16, 2020 by johnholmes

[SMU]

Morning - 

A bit of a lull this next 5-6 days in terms of weather excitement, the milder air wins over the UK for an extra 24 hours ( more especially over the south-

Post that possible interest in the form of snow over Northern Scotland again as the polar air pushes south again-

NB ridge forming up to Iceland on GFS & ECM

S

[Kirkcaldy Weather]

On 15/10/2020 at 12:39, Kirkcaldy Weather said:

I wouldn’t get too concerned at the minute I think the models will be chopping and changing quite frequently over the next few weeks with a few things going on, possible hurricane development I would say toward Florida could be most likely but as always models will struggle to pinpoint until / if it has developed also the ECM and GEM latest runs show the high pressure going well into the arctic from the Pacific side I’m not sure whether that is the most likely outcome but anyhow with phase 5 of the MJO does look like some form of blocking will be the likely scenario, with 2 possibilities of tapping into an easterly on these charts 

if the low pressure stays centred enough to our south or indeed if we do end up with the high over Scandinavia.

Just a few ensembles to highlight the pattern I think is worth looking out for 

hurricane - Florida (some actually hint at another tropical system in the atlantic) 

scandi high 

last one the higher pressure develops bit north of scandi but still same general idea.

 

[phil nw.]

A somewhat different Atlantic profile with plenty of northern blocking being modeled. This is pushing the mean jet flow further south and temperatures suppressed. 

It looks like next week will turn unsettled as low pressure heads towards the UK although still no signs yet of a step up to full on zonality as some positive heights remain to the north.

It is early days in the development of the polar vortex yet though but a pattern like this come late November on would be very interesting to cold lovers. 

 

 

[summer blizzard]

UKMO and GFS tonight have weakened the low at day 6 to the south west of the UK.

 

[Tim Bland]

Cold building to the east on the GEM ..

[Zak M]

You know the GFS ensembles are bonkers when one churns this out at day 6.

Edited October 16, 2020 by Zak M

[I remember Atlantic 252]

6 minutes ago, Zak M said:

You know the GFS ensembles are bonkers when one churns this out at day 6.

easily modeled, brief PM shot as trough moves east, -4 uppers surely nothing unusual of a NW flow in late oct?

[Zak M]

These are the latest GEFS 2m temperature anomalies for weeks 3 and 4. Looks very good for early snowfall.

   

These charts can be found on TheWeatherOutlook's Twitter account, and (soon) their website.

Edited October 16, 2020 by Zak M

[stodge]

The temperature profiles "suggest" a strong block over western Russia feeding S'ly winds through eastern Europe into Scandinavia leaving north-west Europe on the cold side of the trough so more N'ly or NE'ly winds and that explains the increased probability of colder and wetter (snowier on the highest ground) outbreaks.

I have to say I've seen more unsettled GFS 12Z runs but not that many - a dismal rest of the month with a lot more rain and only the briefest of drier interludes.

GEM plays a different set of cards as it did last night with the HP bloc moving further north into the far NW of Russia allowing some early cold air to come further west than you'd expect.

As others have said, we have the wildcard of renewed hurricane activity - GFS brings a powerful hurricane across Cuba and Florida and up the east coast becoming a strong ex-tropical LP - this is often how the Atlantic jet gets fired up at this time of year.  GEM keeps the hurricane out at sea as a weaker feature but brings it NE further south so we'll see.

ECM rolling out now and again the themes are northern blocking and negative alignment.

 

[Mike Poole]

Winter looms larger every day, and it is good to see Stratobserve area back in NH mode:

We watch as the vortex tries to gather strength in October.  Not so much in the next week/10 days, but increasing thereafter, the blurb says all 31 GEFS members are now included in these plots, so we’re in good shape to monitor developments.  

Meanwhile ECM 12z shows the trop vortex is struggling early doors,  here T144 and T240:

The T240 chart looks like some origami gone wrong.  

Edited October 16, 2020 by Mike Poole

[bluearmy]

Liking the runs recently that have shown a propensity for driving the Atlantic trough se under weak upper ridges establishing to our north  - that would be a great pattern to establish - probably the most snowy winter setup  for the U.K. ...

[blizzard81]

57 minutes ago, bluearmy said:

Liking the runs recently that have shown a propensity for driving the Atlantic trough se under weak upper ridges establishing to our north  - that would be a great pattern to establish - probably the most snowy winter setup  for the U.K. ...

Yes, I love to see the Atlantic lows being knocked onto their backsides so to speak - what most would call negatively tilted lows. I remember looking years ago at the archives for early Nov 62 and seeing this rare phenomenon. I kept looking out year after year for these negative tilted beauties and then Nov 2009 came along and hey presto. The rest is history. We are certainly seeing those same signs again in the present modelling. Interesting times. 

[damianslaw]

25 minutes ago, blizzard81 said:

Yes, I love to see the Atlantic lows being knocked onto their backsides so to speak - what most would call negatively tilted lows. I remember looking years ago at the archives for early Nov 62 and seeing this rare phenomenon. I kept looking out year after year for these negative tilted beauties and then Nov 2009 came along and hey presto. The rest is history. We are certainly seeing those same signs again in the present modelling. Interesting times. 

Yes November 2009 saw the longwave trough stuck in situ but to our west hence it was a very mild southerly / south westerly type month until the end, there was a major block to our east; unusual synoptics and suggestive things were not going to be normal that winter. 

The models are showing a very unsettled period ahead with the trough coming unstuck and making a beeline for the UK, anchored directly through the country on a NW-SE aligned trajectory, so becoming chilly as we are locked onto the colder side of the jet with time. Initially we will see some milder uppers more so SE, north will stay cool throughout. This is the type of pattern that gives rise to the 'slider' low and trough in winter which can produce heavy snow, alas to early for that, but highest ground  in the north more so Scotland could see quite a bit of the white stuff by the time the month is out. I was in Aviemore late October last year and there was significant snow above 800 metres, with some harsh frosts.