[Model Output Discussion - moving into Winter]

Gotta say , another fantastic ECM mean.

[Model Output Discussion - moving into Winter]

So we have ECM spitting out almost 2010 like repeats, GEM sorta mixed, GFS got little interest in cold and UKMO probably middle of the pack. One thing in common is that all 3 have a optimistic set of ensembles. The next couple of days is gonna be stressful watching the models roll out

[Model Output Discussion - moving into Winter]

1 minute ago, Allseasons-si said:

Surely this is homing on looking more like a 2010 chart

Its good but follow the air flow and the source is from Central Europe rather than Scandinavia and Russia, unless if your in Scotland where the flow is more easterly sourced.

[Model Output Discussion - moving into Winter]

1 minute ago, TSNWK said:

that is good as suggestive to me that Low over north sea around 180 has little suport?

Correct, you can see the Operational against the mean below. Little support of a random low blowing up out of nowhere. Also much stronger signal for the GL on the mean. 

[Model Output Discussion - moving into Winter]

We can all calm down now , Op was a massive outlier in the MSLP pattern against ensembles

[Model Output Discussion - moving into Winter]

Lets just say…

00z ECM mean is better than 12z

 

it also favours more of an easterly flow early next week compared to 12z

[Scotland Weather discussion]

I gathered in snow reports from this forum and twitter from last nights snowfall and here is what I came up with. The second graphic is what I had forecasted and I am honestly quite happy with how it has turned out! 

[Scotland Weather discussion]

2 hours ago, edo said:

That one has missed us, crazy how a few miles can make such a difference.....need some luck in this set up as to where the beefier ones hit. Only caught a couple of cms here but looks like chance of plenty hitting over next few hours. 

Ended up with 3.5cm here. 

[Scotland Weather discussion]

Some of the heaviest snow I’ve ever seen to the south of Perth! Gone from a light dusting to a good few cm in around 20-30 minutes!

[Scotland Weather discussion]

8 hours ago, Dundeeguy said:

What do we reckon for tayside then? met going with light snow showers throughout the night 

Eastern parts of the region probably won’t see more than a light coating, areas in the West of the region may see 2-6cm quite widely to low levels with 10cm+ over higher ground.

[Scotland Weather discussion]

I have issued a snow watch for tomorrow and Thursday:
 

A cold front will move SE during Wednesday morning before clearing all areas in Scotland by Wednesday evening. Following this front will be colder air but also very low 500mb heights which aids to plenty of instability for widespread shower development. I have also noticed that the air temperature at 500mb is forecasted to be in the mid -40s which is an incredible temperature gradient between the surface and 500mb for heavy wintry showers!. It seems the 500mb temperature is a big factor with the snow showers over the coming days instead of the 850mb temperatures which we tend to rely on more with Pm westerlies as the air at 850mb is only -4C over the coming days which is much lower than we usually see from these set  ups.

As that cold front moves south the wintry showers will quickly move in from behind it and snow will start falling and accumulating to low levels quite widely by the late evening as surface temperatures drop to near freezing. The frequency of these snow showers will increase during the overnight hours and into Thursday morning across many areas ( only exception is the far NE of Scotland ). These showers will be most frequent through the heart of Scotland as highlighted by the MOD risk area on my snowfall graphic. Here I expect 3-6cm quite widely to low levels with 10-15cm falling quite widely above 150m or so , I suspect 20-30cm possible above 300m here. In the LOW severity zone I expect most will see a brief 1-2cm at some point, however where showers merge there could be as much as 5-10cm to low levels I suspect. 

[Scotland Weather discussion]

58 minutes ago, edo said:

oh all snow will go south of Perth.. been a year since seen any snow lying. Very windy and rainy here but nothing too bad.... football was a bit stop start as thr wind blew the ball away constantly. 

I'm frozen though as now on final leg of 3 hours outside as walk the dog... looking fwd to couch and charts that maybe dare me to dream whilst watching some champions league., 

Models look great for us in Perth but I can just feel it going wrong. 
We could get 6-8  hours moderate snow and 10cm+ or not snow and well 0cm. Tomorrow's model runs are crucial. 

[Model discussion - hunt for cold Christmas period 2021]

Just now, johncam said:

No afraid not mate , we are sheltered fron the Highlands to our north so unless exceptionally cold we are lucky to get a frost if its windy 

similar story here in Perth with northerlies , unless if the convective is extremely deep and somewhat organised and there is a strong breeze then there is no chance of snow showers making it down here. Although i would take a northerly over a SW'ly any day.

[Model discussion - hunt for cold - Christmas countdown]

Massive differences between the EPS graphs between Aberdeenshire and Southeast England. 

[Model discussion - hunt for cold - Christmas countdown]

UKMO 96 hours... 

[Model discussion - hunt for cold - Christmas countdown]

Just now, Kasim Awan said:

Yes I agree. Let's see if it makes a difference down the line.

Cold air a good bit further south over the UK at 48 hours and the general low pressure area looks more south. Touchwood of course. 

[Model discussion - hunt for cold - Christmas countdown]

Early days but GFS already looking slightly better by 30 hours.

[Model discussion - hunt for cold - Christmas countdown]

At least 12z Arpege isn't to shabby. We now move onto GFS then UKMO which will soon be followed by GEM. I don't expect further downgrades but don't expect Christmas Miracle type charts. 

[Model discussion - hunt for cold - Christmas countdown]

Time for the Pub run guys! 

[Model discussion - hunt for cold - Christmas countdown]

We will have a easterly across many parts of the UK by the Christmas weekend which is cold enough to produce snowfall. However a blanket of dry

air plaguing the lower troposphere will limit or complete prevent convective from developing which will mean that the easterly will just be a cold wind with status cumulus clouds.  

[Model discussion - hunt for cold - Christmas countdown]

quite a big upgrade from GEFS , low more south with a easterly flow for the north unlike 06z.

[Model discussion - hunt for cold - Christmas countdown]

GFS would cake inland parts of Scotland to relatively low levels , but feet and feet of snow over the higher ground i suspect. 

[Model discussion - hunt for cold - Christmas countdown]

It's that stupid low which spins up to the SW bringing milder air further north, need to watch this in the 12z runs today. 

[Model discussion - hunt for cold - Christmas countdown]

T- 1 hour , 35 minutes till 12z ICON starts rolling out

T- 2 hours , 30 minutes until 12z GFS starts rolling out

T- 2 hours , 45 minutes until 12z UKMO starts rolling out

T-  3 hours till GEM starts rolling out

T- 4 hours , 55 minutes until 12z ECMWF starts rolling out. 

[Model discussion - hunt for cold - Christmas countdown]

1 minute ago, Lukesluckybunch said:

the ens are not out yet.that was maybe this mornings

It's the 12z ensembles which are there.