Retrospective on the last cold spell from the Met Office

[xmetman]

The climate team at the Met Office have been working overtime and have produced a report detailing the events of the recent cold spell which as you know started on Sunday the 25^th of February and lasted to following Saturday the 3^rd of March 2018.

 

[John Hall]

Thanks for the link and charts. A very interesting report. The bar chart of the lowest UK-areal daily maxima back to 1960 is particularly interesting.

[Julian Mayes]

I know that the snow depth measurements have been mentioned on here before - and many contributors will be familiar with the automated measurement system much more than myself - but the pattern on the 2 March map is remarkable. With the 1st march snowfall involving drifting, we have very low depths in Devon and west Somerset ( a 0 at Dunkeswell and a 1cm at Liscombe) but 49 at St Athan, later to become 52 or 53cm.  I assume that snow drifted away from the very exposed sites at Liscombe and Dunkeswell - but it would be interesting if only the St Athan site had a photo series to show the pattern of snow accumulating around the sensor. Certainly, looking at the Vaisala road weather cameras, the images from north Devon looked extraordinary after the event, while those in the Vale of Glamorgan were snowy,  yes, but less deep. The lanes in north Devon simply filled with snow between the hedges, as many may have seen on TV reports.    I am assuming that the peak at Wittering is genuine as it lies in the firing line of The Wash convergence.   

I'm only writing all this to whet my appetite for tonight's snow. That'll do it!  interesting to see the Thames Tickler snow gather now in Essex / Suffolk / Thames Est.    A few more snow flakes coming down here in Molesey.   

Cheers    Julian       

[xmetman]

I'm not so sure about the Wittering snow depths.

It did accumulate very quickly which could have been due to a veer in the strong wind that shifted a snow drift (possibly caused by the rain gauge) towards the sensor.

But we'll never know as all the evidence has long since melted!

I think with the degree of drifting that went on in that cold snap many an observer would have simply reported 49999 in his hourly SYNOP. 

Something similar to what possibly happened at Wittering may have also happened at St Athan.

That's why snow depth data from WOW would have been interesting to see.

I was in Coleton Fishacre a week last Friday (awful weather that day) and there were still the remains of deep drifts down there. 

I did mean to do an estimate from the radar to see the distribution of the showers from the week before, because I reckon the south Hams got a lot of snow from the convergence that was running down the English Channel.

[John Hall]

I don't suppose that code 90 for the depth of recently fallen snow gets used very often. Four metres in one fall would be going some. :)

[Dave C]

Seems a bit late in the spell for maximum snow depths. here the depths had halved by then due to a mixture of sublimation and wind stripping. So whilst 5cm for that date was reasonable it was at least double that earlier on.

[xmetman]

I may be wrong here, but don't the Americans use accumulated snow depths?

If you measure new snow depth every three hours or so and kept an aggregate total, that might better reflect the total amount of snow that had fallen.

[xmetman]

[Ian Ager]

Hi I'm still curious about the Wittering depth. Would that be a manual reading?
I ask as I was unfortunate enough to have to drive from Rushden to Easton On The Hill in the far NE of Northants on 2nd March (work, wouldn't have done it for pleasure)
Horrific drive as I headed the 20 miles NE.
Easton is just 3 miles from RAF Wittering, and to my amateur eye 15cm, hard to tell with so much drifting.
I know Wittering is idealy placed for Wash convergence, but the quoted depths just seem too great.
Was it sensor sensor measured??

Off topic, managed to cut the lawn today!

All the best,

Ian, Rushden Northants.

[xmetman]

Ian

They are probably a mix of both AWS and manual readings. 

I didn't think of highlighting the difference in the graph - maybe next time I revisit the code!

Bruce.

[Paul Kendall]

The snow depth for a High Wycombe reported by AWS over the weekend was far too high. I suspect the area were the snow depth sensor is located was in the middle of a snow drift. I live in High Wycombe and where I live no more that about 3cm but drifts up to about 30cm in a few places.

AWS snow sensors are, in my opinion, useless and misleading when there are windy conditions.

Paul Kendall

[Ian Ager]

Hi Bruce,thanks for the clarification

Ian, Rushden.

[John Hall]

The "new snow" amounts reported for St Athan and Wittering seem to be missing a lot of snowfall, if those snow depth figures are anything like correct. Also what do the red bars underneath the X axis represent?

[xmetman]

John

It's easy enough - blue bars are positive hourly differences in snow depth - new snow.

Red bars are negative hourly differences - snow melt.

You can only do so much with just an hourly snow depth I'm afraid.

It's all in the blog and more!

Bruce.

[John Hall]

Thanks, Bruce. I did wonder if the red was snow melt.