UK Thunderstorms - Spring 2010

[Simon Culling]

Whilst we have a few storms over the winter months, mostly of the one flash + bang variety, and mostly on western coasts of the UK, the enhanced heating of the sun from mid-March starts up the thunderstorm season for much of the UK. With plenty of cold air still aloft, the strong sunshine can create quite a high lapse rate in March + April and generate some very photogenic storms as the air source (from W thru to N) brings clear air. They do not tend to be long lasting or severe, but they are often the most aesthetically pleasing and usually bring plenty of hail with them.

So far, storms have occured on the following days:

12th March, A few over England
22nd March, NW England and SW Scotland
25th March, Southern England - see below
29th March, Kent
30th March, NW England incl Manchester + Liverpool
1st April, Wales (with thundersnow in the hills) + London area
2nd April, Gloucester + Shropshire

The storms on the 25th March were quite active and developed over N France in a moist plume above the boundary layer and drifted north hitting the south coast of England around 4pm, particulatly the Isle of Wight, Hampshire + Sussex, with plenty of c-g strikes and hail. There was a deep low (975mb) to the SW of Ireland and a S flow over the UK at the surface and at 500mb, but at the jet stream level, winds were W. A number of small troughs moved north in the general flow. They managed to travel the 120 miles north to Milton Keynes, but provided only one c-g strike at exactly 18.00 and then died out. C'est la vie.

A house was struck by lightning in the village of Booker, near High Wycombe (Bucks), but the resulting fire only caused minor roof damage.

[NZstorm]

The storms on the 25th March were quite active and developed over N France in a moist plume above the boundary layer and drifted north hitting the south coast of England around 4pm, particulatly the Isle of Wight, Hampshire + Sussex, with plenty pf c-g strikes and hail.

The elevated storms from France tends to be more of a summer phenomena from memory. Interesting that it can happen in March. France is a particularly unstable region in summer with supercells occurring there.

[Simon Culling]

Steven, you are correct about them being more of a summer phenomena, but they do occasionally occur outside of what we call summer, ie June, July and August. They are often referred to as 'Spanish Plumes', and the link below explains it better than I can.

http://forum.netweather.tv/topic/29496- ... ms-setups/

[Simon Culling]

Little or no thunder activity in the UK in April, despite the month being famous for its showers. However, May 1st brought an unexpected storm or two.

A convergence zone became established during the afternoon, extending northwestwards from NW London to central Wales, with NE winds to the N and a S flow to the south. Max temps were only 18*C in the London area, but a sharpening upper trough appears to have combined with the convergence to provide just enough ascent for a few t'storms to develop early in the evening. Here in Milton Keynes I was able to watch the Cb's develop in the gathering evening gloom and below an altostratus sheet that had spread over late in the afternoon, resulting in a decent storm between 20.28 and 20.49 local time. The accompanying rain was torrential at times and hard hailstones up to 5mm fell on a couple of occasions. A local weather station recorded 34.5mm between 19.30 on saturday and 12.00 on sunday (2nd), with 15mm coming from the t'storm.

A small area of low pressure developed over southern England as the upper trough moved SE into Europe and produced between 10-40mm of rain over much of southern England and the midlands, with many places receiving their first significant rainfall for nearly a month.

[Simon Culling]

Not much thundery activity in the UK this spring, but a few brief storms did develop on Sunday 16th May as a cold front moved SE across western and southern England. The low cloud broke ahead of it to give some sunshine south of a line London-Bristol and an area of convective rainfall developed in the shallow moist zone ahead of the front, giving 10-20mm in places, especially to the west + south west of London, with a few rumbles of thunder. Here in Milton Keynes we only had a few showers, so my cricket match wasn't interupted.

It has warmed up in the last few days and despite most of the UK being under upper ridging, some quite nasty storms developed in a convergence zone over the Cairngorm mountains on Friday 21st May. Strong surface heating (up to 23*C in places in the early afternoon in eastern Scotland) combined with the convergence zone (general N flow with an E sea breeze developing on the east coast of Scotland) and 30-40kts of 0-6km wind shear available, triggered a clutch of storms over the mountains, with reports of 30mm+ rainfall in places. Two houses were struck by lightning at Westhill, near Aberdeen, with roof and telephone line damage. A few brief showers/thunderstorms also developed in the late afternoon over the north Pennines (in another convergence zone).

With temperatures expected to reach 27/28*C today, a bit more moisture in the lower atmosphere may trigger a few storms over the mountains of east Scotland (again) and in NE + E England.

[spwill]

What is the most thundery month in the UK, I would guess June.

[Simon Culling]

Hey spwill,

I recall a detailed article on UK Thunderstorm Climatology being published a couple of years ago, but I cant find it at present. When I do, I will be better placed to answer your question.

With regard to annual frequency of thunder days in the UK, it ranges from less than 5 in the northern half of Scotland, to 5-10 days down the western side of England + all of Wales + Eire, to 10-15 in the central strip (north to south) of England, to 15-20 days in SE England (incl London), East Anglia + the East Midlands, ie the SE quarter of England.

[Simon Culling]

For sites that I could find data for, (1961-1990 period), those located in central and eastern England have their peak thunder months between May + August with an average of between 2 and 3 days per each of these months. Western coasts of Wales + Scotland are more likely to have their peak months in the winter as cold air passing over the warm Atlantic is often suffiiciently colder than the sea to generate heavy showers that die out as they move inland over the colder land. SST's are over 10*C on the west coast of the UK in winter, compared to 5-8*C in the North Sea onthe eastern side.

[NZstorm]

The UK thunderstorm environment looks fairly to similar to NZ but we would get more of the winter variety storms here and less summer events. Europe certainly helps to bolster the instability over the SE of the UK in summer.

[Richard]

The UK thunderstorm environment looks fairly to similar to NZ but we would get more of the winter variety storms here and less summer events. Europe certainly helps to bolster the instability over the SE of the UK in summer.

And the east of the South Island is more like England been the other way around with mainly spring and summer storms

[Tornado Tim]

The UK thunderstorm environment looks fairly to similar to NZ but we would get more of the winter variety storms here and less summer events. Europe certainly helps to bolster the instability over the SE of the UK in summer.

If it were Auckland I would agree with you.
As with the Waikato it would be more Spring/Summer as most of the storms here are due to diurnal heating.

[NZstorm]

I agree with Tornado Tim, but I do think the SE of England gets more summer convection/thunder. Northern NZ suffers from the stabilising effects of the subtropical ridge over summer. This ridge favours anticyclones at our latitudes.

[spwill]

Thanks Simon for that information , interesting that Western coasts of Wales + Scotland are more likely to have their peak thunder months in the winter despite the rather cold winter .

[Richard]

You are right NZstorm the SE of England would get more summer convection/thunder between May - August if they are averaging between 2 and 3 days per each of those months,where i am we would only get 2 or 3 for the whole of the spring/summer,but as for winter we experience no storms at all,apart from areas around Banks Peninsula and along the mountains, though some spillover sheet-lightening can spreed further east but very only rarely.

[spwill]

Agree with NZstorm that NewZealand would see more winter thunderstorms than England but they mostly occur in the West of NZ also coastal Southland and the far north

[Simon Culling]

Interesting discussion gentlemen. You are correct to note the influence of heat from the European continent as an important contributor to thunderstorm days in the SE of the UK. The reference in the third post of this thread gives further details re the Spanish Plume type events, but many of the storms over England are home grown in showery SW, W, NW or N airstreams. However, the longer lasting storms tend to come up from the south, ie France. Very occasionally, supercells can form in-situ over England, usually in association with occluding frontal systems with very warm + moist air sourced again from the south + south east eg the T5 tornado in Birmingham on 28/7/05.

I have constructed a table in excel with details from 13 UK stations re monthly thunder days, but cant work out how to format it so as to display it here - like a photo. Any ideas?

[Simon Culling]

A few more storms in the last week of spring.

Sunday 23rd May: A high pressure (1027mb) was centred over souther England with a subsidence inversion at 750mb, but this was less apparent ove the north of the UK where the presence of more low level moisture was sufficient to break the cap, and a few sea breeze convergence zone storms broke out over eastern Scotland and NE England.

25th May: Significant storm develpment over northern France, with a few storms making it to Jersey.

26th May: A few storms in NW England (particularly Cumbria) and E Scotland. 4 people were struck by lightning in Cumbria in 3 seperate incidents. See story at link below

http://news.bbc.co.uk/1/hi/england/cumbria/10167686.stm

27th May: A few storms in NW England and S+E Scotland, with reports of hail to 1cm in Wrightington, Lancashire and Motherwell, Scotland. A small tornado was reported from Neyland, Pembrokshire in S Wales, with 2 houses suffering roof damage. A church in Dundee was struck by lightning + its spire badly damaged.

http://news.bbc.co.uk/1/hi/scotland/tay ... 181486.stm


Possible 'Spanish Plume' event this weekend, giving some elevated storms over S England, especially the SE incl London. Will start a new thread for summer.

[spwill]

UK being well populated you would get good reporting of severe weather.

[Janos]

Seemed to be on the edge of a few of those heavy showers today. I am surprised at just how warm/hot and humid
its been. Dear I say it I think so far the summer in Berkshire has been considerably more settled and warmer than what I can remember back in Dunedin.

[Simon Culling]

spwill, you are right about the greater population density, although large areas of all the 4 nations in the UK are sparsely populated, especially the Scottish + Welsh mountains and the Pennine mountain chain that runs down the spine of northern England. It does help having more eyes watching, and the proliferation of digital camera's and mobile phones means that many of these events are now recorded.

Janos, I'm not sure about the warmth so far this year - the CET for May was -0.5*C below average, although June is currently running a couple of degrees above average. The forecast for the week ahead is for much cooler and significantly wetter weather - we have been drier than average here in the UK for over a year now

[Janos]

We are enjoying one of the best summers that i have experienced compared to what we got back in Dunedin.
Interestingly my colleagues on the estate are suggesting this is an ok summer.
Id certainly like to experience a good summer here.
Most days seem consistently warm to very warm and humid.
Even got sun burnt today !

[spwill]

Yes, the humidity in the south of England is something you dont get in the SouthIsland of NZ due to the Mnts/high country however England can certainly get crap summers even in the south.


Mosgiel over the hill from Dunedin has a much better summer than Dunedin City

[Janos]

Valid point i do forget that Berkshire is land locked but every day this week temps are on the rise from the mid 20s hitting a high of 29 on Sunday. I guess what has really surprised me is the fact that the period of settled weather seem to last between 4-7 days ..cool one week i.e high teens hot the next mid to high 20s. The humidity was also a surprise to me anyway its most enjoyable sitting outsdide most evenings and not getting the Easterly wind in our faces.

[NZstorm]

I remember it used to get really hazy in London when the humidity went up. So when the weather turned unstable you couldn't really see the clouds.

[Michael]

Never been to England though my pictures of it is the eastenders look where you see it overcast with a gale but then at timesreading the paper after seeing it on 18 deg for long periods in july suddenly its 34c even auckland never gets that.