UK Convective General Discussion & Forecasts

[Thundery wintry showers]

Thunder frequency has indeed declined across most of the UK over the last couple of decades. Philip Eden wrote about this in the Telegraph last weekend, and his book "A Change in the Weather" (2005) highlighted a general drop in the 1990s and early 2000s relative to most earlier decades, with an average of 2 thunder-days per month over England and Wales as a whole instead of 3 or 4.

I think the decline in the 1990s primarily stemmed from an increase in dry stable anticyclonic weather, but can't be sure why it hasn't recovered significantly in the 2000s despite a shift back towards more changeable westerly-dominated summers.

I find the "10 countries with most thunderstorms" table's stats believable but am left suspecting that they may have only considered a small subset of European cities.

[Coast]

Thunder frequency has indeed declined across most of the UK over the last couple of decades. Philip Eden wrote about this in the Telegraph last weekend, and his book "A Change in the Weather" (2005) highlighted a general drop in the 1990s and early 2000s relative to most earlier decades, with an average of 2 thunder-days per month over England and Wales as a whole instead of 3 or 4.

Did find this by Philip from a few months ago:

June 28, 2011

The English Summer ...

... two fine days and a thunderstorm

By Philip Eden

The English summer, it has been said, consists of two fine days and a thunderstorm. This assertion is normally attributed to George II, although Richard Inwards' volume, Weather Lore, perhaps wisely regards its originator as anonymous.

Whatever its genesis, this view is probably nearer the mark than the more romantic image of high summer weather in Britain - long, hot, hazy days in the sun, crowded beaches, parched gardens, and so on. The summer months do from time to time comprise a succession of days of blazing sunshine and soaring temperatures, but these years are rare enough to become imprinted on the community memory - 1900, 1911, 1921, 1959, 1976, 1983, 1990 and 1995, for instance.

Just as infrequently, the summer contains no extended settled spell at all and only a few days when the warmth of the sun allows us to shed the ubiquitous mackintosh. The last time this happened was in 2007. Between these two extremes we can find most of the summers we experience in Britain, usually containing one or two of those short heat-waves followed by thunderstorms - we are experiencing one now - with plenty of indifferent weather between.

Professor Hubert Lamb, one of Britain's best-known climate experts, analysed weather patterns over 100 years to determine whether any particular patterns tended to recur at certain times. While acknowledging that our weather varies widely from year to year, Lamb did succeed in determining several recurrent themes which he called "singularities". It was important to explain why these climatic preferences happened at specific times of the year, rather than regard them as mere statistical quirks, and this he was able to do as well. Nevertheless, he emphasised that his singularities were not regular enough nor reliable enough to be used as a forecasting tool.

Lamb dubbed the period mid to late-June the 'return of the westerlies' and mid to late-July 'thundery and cyclonic'. After several months, from February to early-June, when winds from a westerly quarter are conspicuous by their absence, they return with a vengeance around mid-June. In late-May westerly winds blow in only 15 per cent of years, but by June 20 the frequency has increased to 52 per cent. During July, the frequency of westerlies declines slightly to about 40 per cent while cyclonic weather types become more frequent, reaching a peak of 35 per cent by the end of the month.

http://www.weatheron...it&DAY=20110628

Edit, found a better article from last year now:

[staplehurst]

Coast isn't that article pretty much the same one that appeared in last Saturday's Daily Telegraph next to the actual Weather section?

[Coast]

Coast isn't that article pretty much the same one that appeared in last Saturday's Daily Telegraph next to the actual Weather section?

Didn't see that one, but this is definitely from a year ago at least (from our friends over at UKWW http://www.ukweatherworld.co.uk/forum/forums/thread-view.asp?tid=37724&posts=18 )

[staplehurst]

Didn't see that one, but this is definitely from a year ago at least (from our friends over at UKWW http://www.ukweather...=37724&posts=18 )

Ah fair enough, just checked in the office as we have a copy from last Saturday and it is exactly the same article, just reprinted a year later. Crafty!

[Harry]

Talk about adding insult to injury...from the BBC website!!!

[Coast]

Talk about adding insult to injury...from the BBC website!!!

That was only one of our aircraft on the way back from Libya......

Now strangely in the States, they area apparently having more severe storms that cost them more in losses:

Thunderstorm losses since 1980 have become five times more severe, on average. There were $20 billion in such losses by midyear in 2011, doubling the average of the past three years.

“The nation is increasingly vulnerable to extreme weather,” National Weather Service Director Jack Hayes says. The year has been marked by floods, drought and tornadoes, such as the May twister that killed 160 people in Joplin, Mo. Meanwhile, a Texas heat wave has cost $5.2 billion in crop and livestock losses so far “It doesn’t take a wizard to predict that 2011 will go down in history,” Hayes says.

http://climatesignal...500-since-1980/

"We want to try to get every community in the USA storm-ready," said International Association of Emergency Managers USA President Eddie Hicks, who heads the Alabama Emergency Management Agency. Discussing the Indiana stage collapse, Hicks called for improved social-media tools to text message warnings to people about weather dangers.

With roughly half of the U.S. population of 311 million living close to the nation's coasts, and economic growth in Southern states hit hard by the tornadoes and flooding this year, Hayes says the nation faces an increasing risk from extreme weather simply because of demographics.

The old record-setting year for nine billion-dollar U.S. weather disasters was hit in 2008, according to National Climatic Data Center records. The center adds up disaster costs using insurer, state and federal agency records going back to 1980.

With NOAA forecasting an "above-normal" hurricane season — seven to 10 hurricanes — after three years without one hitting land on the East Coast, "I'm very worried about complacency," Hayes says. "We want people taking steps now to be ready for extreme weather."

http://www.usatoday....disasters_n.htm

[Lauren]

Talk about adding insult to injury...from the BBC website!!!

Would you get electrocuted if you were in the tower at the time, considering all the metal?

[Harry]

I would have thought not...the Eiffel Tower I suspect has a pretty sophisticated lightning conductor (in addition to itself being a fairly proficient conductor). Lightning will also take the route to earth which offers the least resistance - could be completely wrong with that though!

I am not convinced the photo shows the Tower getting hit, but the stroke landing immediately behind...again, could be completely wrong with that though.

[NO LONGER POSTING]

Would you get electrocuted if you were in the tower at the time, considering all the metal?

I did an electronics degree..

But I wouldn't think so..The electricity wants to flow the quickest way possible..So if you are wearing rubber shoes you are stopping the connection but if you weren't wearing shoes yes as the electricity can flow through you..

The sheer amount of current and amps in a lightning bolt is a lot as we all know..

But electricity can jump too..What a lightning bolt is..

I would say yes and no depends..

[Coast]

Would you get electrocuted if you were in the tower at the time, considering all the metal?

I guess it's a Faraday cage: http://en.wikipedia.org/wiki/Faraday_cage

[Lauren]

I guess it's a Faraday cage: http://en.wikipedia....ki/Faraday_cage

But what if your holding on to a railing or something else metal? Most of the floor is metal in that tower!

[Coast]

But what if your holding on to a railing or something else metal? Most of the floor is metal in that tower!

http://www.mos.org/sln/toe/cage.html

http://www.mos.org/s...skineffect.html

http://en.wikipedia.org/wiki/Skin_effect

[Harry]

But what if your holding on to a railing or something else metal? Most of the floor is metal in that tower!

I think it would depend on the quality of the conductor on the Tower...if the conductor is of very high conductance, the lightning should travel to earth via this. Remember that electricity will always take the route to earth offering less resistance.

When we touch things which have become electrified, if we're shocked it is because the object isn't sufficiently earthed. For example, sometimes when you get out of a car you get an almighty shock, resulting from a build up of static electricity. The car isn't sufficiently earthed as the only part of the car in contact with the ground are whopping great rubber tyres - the electrical potential cannot travel through these to get to the ground so remains on the car's shell. When we get out of the car and touch the door with our hand, the moment we touch the ground with our feet we are earthed and offer the charge a means of escape. It is then we feel the shock.

In the case of the Eiffel Tower, the lightning conductor has no great rubber tyres preventing sufficient earthing. Therefore, the electricity will zip to ground having no inclination to go through us. IF, however, the lightning conductor is broken (cables snapped/corroded) such that our bodies offer less resistance, then I think a shock would be possible.

I'm trying my best to regurgitate my physics' lessons

[Coast]

It's been happening for a long time and I've not heard of anybody being killed or electrocuted

[Harry]

(SE-centric post, apologies)

Oohh this looks interesting, although slightly at odds with GFS (zip to Saturday night)

http://www.metoffice.gov.uk/weather/uk/se/se_forecast_weather.html

Note it was updated about 40 mins ago

Edited September 1, 2011 by Harry

[staplehurst]

(SE-centric post, apologies)

Oohh this looks interesting, although slightly at odds with GFS (zip to Saturday night)

http://www.metoffice...st_weather.html

Note it was updated about 40 mins ago

yeah, but those symbols have been there all day. What is interesting is the UKMO Global model is overly keen for a plume-like event, whereas the GFS is backing off the idea - usually the other way round!

[Lauren]

I think it would depend on the quality of the conductor on the Tower...if the conductor is of very high conductance, the lightning should travel to earth via this. Remember that electricity will always take the route to earth offering less resistance.

When we touch things which have become electrified, if we're shocked it is because the object isn't sufficiently earthed. For example, sometimes when you get out of a car you get an almighty shock, resulting from a build up of static electricity. The car isn't sufficiently earthed as the only part of the car in contact with the ground are whopping great rubber tyres - the electrical potential cannot travel through these to get to the ground so remains on the car's shell. When we get out of the car and touch the door with our hand, the moment we touch the ground with our feet we are earthed and offer the charge a means of escape. It is then we feel the shock.

In the case of the Eiffel Tower, the lightning conductor has no great rubber tyres preventing sufficient earthing. Therefore, the electricity will zip to ground having no inclination to go through us. IF, however, the lightning conductor is broken (cables snapped/corroded) such that our bodies offer less resistance, then I think a shock would be possible.

I'm trying my best to regurgitate my physics' lessons

Thanks for simplifying things for me. My physics is not my strongest subject.

I guess I just figured that on the way down to the floor that lightening might pass through you if you were touching something metal.

[Coast]

I guess I just figured that on the way down to the floor that lightening might pass through you if you were touching something metal.

Just don't go up the Eiffel Tower without a tee-shirt.....

[Coast]

Here we go, its down to good lightning rods/conductors:

The phrase “lightning never strikes twice” is not correct. The fact is that lightning can strike the same structure time and time again. The Eiffel Tower for instance was struck ten times during one lightning storm.

To fully protect a building from a direct or indirect lightning strike a Risk Assessment needs to be carried out. Once the need for Lightning Protection is established a system needs to be designed specific to the structure under review. A traditional “Faraday Cage” system comprises of copper or aluminium roof and down conductors and earth terminations i.e. of earth electrodes deep driven in to the ground.

Metallic elements of the structure such as metal clad roofs, parapet capping, structural steelwork, structural reinforcing, pile caps etc can also be used if they comply with the criteria laid down in BS EN 62305:2006. Surface fixed conductors should be pvc sheathed colour coded to match the fabric of the building. Brown, black, grey, stone, white and green being the colours most readily available.

Individual earth termination must attain a specific resistance to earth. The requisite resistance is dependent on the number of earth terminations in the system and is calculated thus: 10 x the number of earth terminations in the system. For example a system with 5 no. earth terminations; the maximum resistance should not exceed 50 ohms. A system with 15 no. earth terminations; the maximum resistance should not exceed 150 ohms. The overall resistance of the system should not exceed 10 ohms.

It is essential that Lightning Protection Systems be designed, installed and maintained by trained and competent engineers.

I shan't quote the source as they are a commercial installer of systems!

[Harry]

yeah, but those symbols have been there all day. What is interesting is the UKMO Global model is overly keen for a plume-like event, whereas the GFS is backing off the idea - usually the other way round!

Where do you acquire the UKMO Global model? Is it a NW extra thing?

If it's not do you mind posting a cheeky screen shot for Saturday night please

Oh found this

[staplehurst]

Yup, it also makes up the BBC graphics for Saturday night. Notice how the MetO have removed their thundery symbols now for Saturday night? Probably from the 12z Global model yet to be released, which will no doubt shunt it a little further east.

[Harry]

Yup, it also makes up the BBC graphics for Saturday night. Notice how the MetO have removed their thundery symbols now for Saturday night? Probably from the 12z Global model yet to be released, which will no doubt shunt it a little further east.

So they have.....

:cray:

[Purplepixii]

Wow it's an interesting topic and one that requires more investigation on my part I think but I only have a couple more weeks to do that before I go back to college and do my 3rd/final BSc year at college. If I were studying weather (darn it - should I have done?) I'd be looking into the decline of UK thunderstorms over the years for my dissertation but unfortunately that wouldn't be appropriate for my current course lol.

As an aside, I remember when I was a kid (1970's-80's) that there were many overnight thunderstorms - so much more than we get now! It's still a standing joke between me & my (younger) sister about how I would climb into her bed during night storms coz they scared me so much! Oh how things have changed

[Chris K]

Very interesting. Also nice to see we may get another little kick of thundery showers before summer is out proper and we decend into full on autumn.