Model output discussion - Winter approaches

[kold weather]

Got to say the 18z doesn't evolve the way we really want it, however there are a fairly high number of ECM ensemble members that aren't that different by 240hrs with LP strengthening either to our NW or N. 

Some move it close enough to pull in a decent WNW, some get it far enough east to drag down some form of cold air, others end up us back in a net W/SW type airflow. Plenty to get through before that point however.

Its not a bad run later on, but its certainly not a great one either past a marginal easterly airflow.

Edited November 23, 2020 by kold weather

[bluearmy]

Today’s runs have merely complicated the outlook ....for coldies today has been a case of one step forwards and two steps backwards wrt to week 2. 

[booferking]

Ec46 out shortly tonight?

[Zak M]

Just flicked through the 12z GEM ensembles and quite a few perturbations are showing some colder options on the table. The GFS is also showing some colder perturbations too.

   

ECM mean @240 is showing the building blocks of a northerly, with height rises in the N Atlantic:

And look at the ECM clusters...

33/51 of them are showing some sort of northerly at around day 10-11 - some agreement there but we need this to be in the reliable timeframe (<5 days)

So there is clearly some signals for a colder start to December... overall it’s looking positive going forward. Let’s hope some of these charts actually verify this time!

(Narrator): They didn't...

Edited November 23, 2020 by Zak M

[Benny123]

That Easterly feed is advecting some pretty potent air temps below 850hpa.

[blizzard81]

8 minutes ago, booferking said:

Ec46 out shortly tonight?

I generally find that no news is bad news on this subject lol. 

[feb1991blizzard]

2 minutes ago, blizzard81 said:

I generally find that no news is bad news on this subject lol. 

Its not terrible.

[kold weather]

13 minutes ago, Zak M said:

Just flicked through the 12z GEM ensembles and quite a few perturbations are showing some colder options on the table. The GFS is also showing some colder perturbations too.

   

ECM mean @240 is showing the building blocks of a northerly, with height rises in the N Atlantic:

 

And look at the ECM clusters...

33/51 of them are showing some sort of northerly at around day 10-11 - some agreement there but we need this to be in the reliable timeframe (<5 days)

Having looked through the actual ECM ensembles there really is quite alot of disagreement actually despite what the clusters suggest, though quite a few do have some sort of N/NW influence at day 10, but many are what I'd describe as at best glancing blows, or limpet northerlies/north-westerlies that won't be nearly cold enough aloft for any all that interesting outside of maybe high ground in the north.

Below average though still favoured on the ensembles, but its cool rather than cold on a great many of them.

Edited November 23, 2020 by kold weather

[Uncertainty]

Last Wednesday, I posted the GEM ensemble at 340, shown here:

Next, today’s 12z at 216.

The ECM mean for comparison.

 

Commendable, if it verifies.

Weeks 3 and 4 also significantly improved vs last week in the EC 46. In some ways it has returned to what it had been showing a couple of weeks ago for this same time period.

Precipitation anomalies for week 3 suggesting higher pressure to the North West and the SLP anomaly backing this up 

We’d need a favourable orientation of the Atlantic ridge for snow but it’s an interesting and unusual pattern for this time of year. 

Week 4 is a bit more vague but still some blocking at higher latitudes and no slug.

Week 5 is horrendous but a long way off thankfully.

In all fairness, the multi-model mean for December from the Copernicus suite was suggesting this kind of pattern so it would be a good forecast if it came off. Thanks to Simon Lee for these charts.

 
Recent history is against us on the potent Northerly front but I don’t actually remember seeing such an intriguing mean Atlantic ridge setup over the last few winters. The fact that it’s forecast quite significantly by a good proportion of the NWP means it’s an option we have to consider.

The GFS, in typical panto villain style, presents the grim alternative.

 

 

Edited November 23, 2020 by Uncertainy

[Allseasons-Si]

Hey,late to the party

but the control is showing what the ecm was showing yesterday evening.

so still the possibility for some snow flurries.

 

[Mr Frost]

Here are the more interesting charts from the latest ECM Monthly Temperature (T2m) anomalies - weekly breakdown below:

30/11 to 06/12:

 

07/12 to 13/12:

 

14/12 to 20/12:

 

I will take that - no blowtorch signal and average for us...that at least gives us a chance of a wintry snap during the above period. (Last week of December into January trending slightly above average)

Not really interested/excited about the upcoming seasonal spell - let’s be honest daytime maximums of 5/6C in the North and 7/8/9C in the South through Thursday to Sunday. 

Here is my forecast for up here: 

Risk of frosts UK and Ireland wide which will be lovely - cloud lingering overnight/clear spells/fog as to who gets lucky!

Wee snapshot of Thursday at 00:00 from the UKV:

 

One week left until the official start of Meteorological Winter - would be nice to see some wintry weather (lowland snowfall) appear on the charts within the next two/three weeks! (Reliable timeframe of forty eight hours )

Proper cold PM NW’ly or Arctic N’ly please to get us started - seems the best bet at the moment!

All the best to you all.
 

Edited November 24, 2020 by Mr Frost

[kold weather]

7 minutes ago, Mr Frost said:

Here are the more interesting charts from the latest ECM Monthly Temperature (T2m) anomalies - weekly breakdown below:

30/11 to 06/12:

 

07/12 to 13/12:

 

14/12 to 20/12:

 

Looks like we will end up in a weak Atlantic situation with the upper trough axis being probably close by to the UK with the main frontal zones probably being to our south which is reflected in the precip maps above. Also means the worst of the above average air is kept to the east, but whilst we keep this pattern there is only limited chances for anything beyond cooler than average to show up, probably from the NW in that type of set-up.

The worry has to be that this period is as good as the background synoptics are going to get, especially if we do not any stratospheric disruption for the 2nd half of winter. I know its somewhat decoupled right now, but I always worry about how long such a situation can hold for.

Edited November 23, 2020 by kold weather

[northwestsnow]

EC 46 is an improvement for coldies ..

[Met4Cast]

EC46 isn't without interest in weeks 2 & 3 in particular. It's good to see a signal for lower heights into Europe by week 3.

Week 2:

Week 3:

[Allseasons-Si]

The day ten mean18z is an improvement on the 12z where it was flat across the Atlantic,more of a trough digging down from the NW into the UK

GEFS mean at 240 v's the ECM

There is still quite a few options on the table in the gefs ens at day ten,heights are stubborn to are NE forcing trough to drop down in the vicinity of the UK,some heights are stronger/further north to our NE with easterly winds,some have higher heights to our west forcing a northerly of sorts and some with heights over the UK with some chilly nights with fog and frost

i feel a standoff is still on the cards with the Scurasian high and Atlantic high,which will become the strongest will determine the weather,IE:-

stronger the Scurasian block,possible easterlies

stronger the Atlantic block,possible northerlies

my gut is the Atlantic block winning out,just my opinion looking at the anomalies.

 

but we need this Atlantic block further north and more amplified otherwise we would just get a cool possibly cold polar maritime nw'ly flow.

Edited November 24, 2020 by Allseasons-si

[Allseasons-Si]

Now here is an irony for you

gefs ens for my local and for London

some of the London ens are trending colder by next weekend with more of a snow row than here

this suggests to me that the se of the UK will have more of an influence from a continental source of cold air

but i must stress,look how much scatter there is from days 4-5.

[Scandinavian High.]

After dryer frosty spell the Atlantic push struggles to get in with everything going south east . Edit looks like Easterly wants set once again.

Edited November 24, 2020 by abbie123

[Ali1977]

I don’t for one minute think it’ll be there on the next run but this is an interesting FI. Low pressures filling up the med and a high pressure building to our E/NE.

[Ali1977]

Cracking day 10 on the way with heights Diminishing any LP to the NE of Canada. If those heights near Newfoundland head North we’ll be in BOOOOOOM territory 

[Mr Frost]

Morning all

This will do! 

You guessed it...ECM day ten! 

North:

 

South:

Full UK and Ireland view!

 

That is how you start Meteorological Winter! Let’s count this down now into the reliable timeframe... 

Have a good day everyone!

[joggs]

17 minutes ago, Ali1977 said:

Cracking day 10 on the way with heights Diminishing any LP to the NE of Canada. If those heights near Newfoundland head North we’ll be in BOOOOOOM territory 

It looks like a west based nao could follow on from that imo. Hope not. Would love a potent northerly.

[mb018538]

Low 500mb heights, decent 850s.....and it's December! Plenty of snow showers packing into the NW off the Atlantic and Irish seas there. People in the NW would love this chart to verify!

[Nick F]

Seems to be some reasonable consistency in the last 3 EC deterministic runs to pull a lobe of the trop PV S and SE towards northern Europe while upper ridge amplifies N over the far NW Atlantic early few days of December - which could trigger an arctic-sourced northerly. But the GFS not hinting at this yet.

GEFS mean in the medium range and yesterday’s  CPC 8 to 14 Day 500mb Outlook points to Canada looking blocked with the TPV displaced over towards Siberia, while energy going into STJ over southern states forming a trough over southeastern US which teleconnects to NW Atlantic ridging. All good ingredients to amplify the flow and allow upper trough to dig deep into Europe. But where the axis of the trough digs is crucial, we don’t want the axis too far west otherwise we are the mild side.

[Tim Bland]

Awesome ECM this morning GEM also looking good with some snow in the South East...

[Day 10]

Day 10 loves Day 10!

All change by tonight no doubt.

On a serious note though, good looking start to Winter from a coldie perspective especially when considering the dreadful last few. Still plenty of possibilities on the table, some of which look pretty good.

Edited November 24, 2020 by Day 10