THUNDERSTORMS are expected to break out across many areas this week, but how can you tell how far away a thunderstorm really is?
Thunderstorms are forecast to hit the UK unleashing heavy downpours which could lease to flooding and disruption. But as large swathes of Britain are covered by severe weather warnings issued by the Met Office this week, how can you tell how far away a thunderstorm really is?
The Met Office has issued a severe weather warning for the UK this week.
There is a second warning for thunderstorms in effect across southern England and Wales.
The warning advises that slow-moving heavy showers and thunderstorms may lead to disruption due to flooding.
In some places up to one inch (20-25mm) of rain could fall in an hour with the potential for 1.2 to 1.6 inches (30-40mm) in 2 or 3 hours in a few spots.
The warning covers areas in the following regions: East Midlands, London and South East England, East of England, South West England, Wales and West Midlands.
Met Office Chief Meteorologist Neil Armstrong said: “Although some places will miss these heavy showers and thunderstorms, where they do occur they’ll be quite lively bringing torrential downpours with 25 to 35mm rain falling in an hour and a few places seeing perhaps 40 to 50mm rain in a couple of hours.
“With this heavy rain falling in a short time we could see some disruption to transport or damage to properties due to localised flooding, as well as the chance of lightning and hail.”
Deputy Chief Meteorologist Martin Young said: “As winds swing to the southwest over the weekend it’ll turn fresher and breezier and east coastal areas should lose the low cloud and mist, feeling warmer here as a result.
“On Saturday we’ll see a spell of rain moving across the UK from the west, but most can expect a drier day on Sunday.”
Throughout much of this week, much of England and Wales will be unsettled.
On Thursday, there will be spells of showery rain, heavy at times, will affect much of England and Wales before spreading into parts of Northern Ireland and parts of southern Scotland later.
It will be brighter over southern England later, but then some thundery showers expected.
On Thursday night, there will be spells of showery rain will affect parts of northern and western UK overnight.
Early evening thundery showers over parts of southern England will soon fade.
On Friday there will be a mixture of cloud and bright or sunny spells across the UK and there will be a few showers about but not as heavy as earlier this week.
How to tell how far away a thunderstorm is
Thunder can always be heard after lightning stikes because light travels significantly faster than sound.
Lightning is the discharge of electricity which travels between clouds or to the ground.
Whereas thunder is the rapid expansion of the air in response to the lightning’s intense heat.
Both the lightning and thunderclap are generated simultaneously but with the speed of light at 299,792,458 m/s and the speed of sound at 340.29 m/s, there will always be a gap between the two to the observer.
At times lightning may be seen, but no thunder is heard.
This may be because the storm is more than 12 miles away (20km) away or because the atmospheric conditions lead to sound bending upwards and away from the surface.
There is a simple method for calculating your distance from a lightning strike.
You simply need to count the number of seconds which pass between a flash of lightning and the crack of thunder which follows it.
Then you divide that number by five.
The resulting number will tell you how many miles you are away from where the lighting has just struck.
For example, a five-second gap indicates the lightning struck one mile away.
If you wish to find out how far the storm is in kilometres, you simply need to divide the number of seconds by three.