Ben Sainsbury

Just so everyone is clear about the Met Office Warnings, Yellow Warning of Snow is Valid from 8am. Amber Warning is Valid from Midday. If we were to expect a red warning, would expect sometime between 12-4pm.

Area of light snow to or south seems to be gradually increasing in intensity. Um got a covering here and I thought we had no snow??

Personally to me looks less marginal for us and more comfortably within the band of snow rather than the edge. Really now any eastward shift won't affect us with all that snow to our west.

NMM 18z, present another larger eastern shift.

My school/sixth form have just closed for tomorrow, something I didn't expect was thinking about Friday. Chew Valley School for those who wonder. (Near Dundry)

Few high res models modelled this, probably as a result of moisture advection for the Storm Emma.

Just to add, Ian said give or take 30 miles or so of white dotted boundaries.

Beat me to it bugger!

Ian’s thoughts on points west. Said about 30-40cm poss in most affected areas between 2 dotted lines.

High-res NMM model looking much better to me, a slight push eastwards. This is 4pm tomorrow, 12z first, 6z second.

I actually think that area circled on the accumulation chart will receive a red warning, seems best location.

Have to agree, but yeah GFS 12z looking a little better.

Ah that helps, cheers!

4th Place? Do you mean within the verification stats of the high res models, excluding GFS, ECM etc. A little confused?

To add the ICON and NetwX NMM look to go hand in hand. GFS, ECMWF, ARPEGE, HIRLAM all point towards heavier, more widespread snow.

Not hugely but still a somewhat small west shift, Bristol throughout looks to be the far far edge. However I can't even trust high-res models, all of the showers the Bristol area witnessed yesterday, not one high-res model forecasted that. I always wonder whether the batch of snow will still correct eastwards as that is the general theme with these events.

And obviously as it stands we have an Amber warning out, we sit under the Highest Impact and 3rd Likeliness of happening. All it takes is for the Met Office to be 90% confident or so (few hours before the event) an in theory should be a red.

The only website I’ve seen possible snow accumulations mentioned was one of the Met Office graphics on Twitter was that 20cm was possible Thursday, and 0-15cm on Friday. Personally not worried about precipitation intensity, I think it’ll produce the goods we are looking for.

Agreed, merely eye candy as all precipitation is accounted for in its accumulation. As inaccurate as these snow depth charts normally are, my intention was just a case of showing how well the ECM has delivered (snow depth wise) compared to other models/previous runs.

For what I see the ECM 12z will have produced some of the largest snow totals of all the runs so far. Exceptional chart, the hardest hit being the Dublin area receiving almost 65cm of snow between Thursday and Saturday. Whilst most other places looking in excess of 20-25cm.

As the large potential snow event has now come into range on the NetwX MR model, I was intrigued to have a look. Can safely say I'm in shock and as unlikely and unpredictable it is to forecast as far ahead as Thursday. We're looking in excess of 18 hours of snow and as the rain to snow ratio is approximately 1:6, we're looking at 15cm+, likely much more. Just for fun tho and taking with a massive pinch of salt but interesting nevertheless given no marginality.

Small 850hpa temperatures changes up to T96 on the GFS and ECM, ECM maybe 6 hours behind in bringing in the cold, but a deeper cold pool over Russia.

I completely agree with you, without the ECM I have little confidence that the other big models are likely to get the pattern nailed on. At the beginning of the SSW event, many of the models were playing with the idea of high moving NE across the UK, but as a whole the models generally flipped between cold & mild setup. I only feel once the ECM caught onto the pattern, that many of the other models were beginning to firm up on the pattern we are looking at. Given its such a complex setup we are looking at, the verification statistics and the exceptional vertical resolution of the ECM that it would be stupid to ignore personally. The ECM has the largest capability of correctly modelling this pattern. But as many of you have said, almost all the other big models have consistency forecast a very cold pattern for several days now with good cross agreement, so who knows.

This is where I disagree, for the deep cold we are most certainly looking a week away. But for the general pattern we are looking at 72-96 hours at most; we are very close to nailing this upcoming spell. (Although the GFS seems to bring the cold in 12 hours earlier compared to the ECM)

How can I identify where a trough exists on the charts?