How do thunderstorms form?

With the heat, humidity and thunderstorms over the UK, I thought I’d share some facts about thunderstorms.

Click below to watch a playlist of lightning videos posted today from England, 26th May 2017 storms.

 How do thunderstorms form?

  • Thunderstorms develop when the atmosphere is unstable – this is when warm air exists underneath much colder air. As the warm air rises it cools and condenses forming small droplets of water. If there is enough instability in the air, the updraft of warm air is rapid and the water vapour will quickly form a cumulonimbus cloud. Typically, these cumulonimbus clouds can form in under an hour.
  • Thunderstorms generally occur in the summer when there’s lots of warm air around and plenty of heat and moisture, but less commonly they can occur in Winter and this does lead to what’s known as thunder snow when thunderstorms occur when it’s snowing.

What is Lightning?

  • Lightning is essentially a giant spark that occurs either within a cloud or between the cloud and the ground
  • The charge and lightning develops because of tiny collisions between ice particles within the cloud. This happens millions of times per second and as these charge particles then spread apart within the cloud larger regions of charge develop and when this charge gets large enough a lightning strike occurs.
  • A negative charge forms at the base of the cloud where the hail collects, while the lighter ice crystals remain near the top of the cloud and create a positive charge.
  • The negative charge is attracted to the Earth’s surface and other clouds and objects and when the attraction becomes too strong, the positive and negative charges come together, or discharge, to balance the difference in a flash of lightning (sometimes known as a lightning strike or lightning bolt). The rapid expansion and heating of air caused by lightning produces the accompanying loud clap of thunder.
  • When lightning strikes it sends out pulses of radio waves and these can be used to detect lightning strokes. You can either use triangulation to work out the direction the lightning strike came from.

To view the best of the internet’s live lightning websites, click through to the “Current” page and there is a Lightning section.

Here’s a recently posted video by Weatherman, Liam Dutton, on predicting thunderstorms.