Sunshine and showers – the time lapse movie
Yesterday’s sunshine and showers littered the sky with towering cumulus clouds that zipped by on the breeze. Some places basked in sunshine whilst others braved the downpours.
The April showers encouraged you to send some great photos me on Twitter, but one thing that really caught my eye was a time lapse video of the skyline above Norwich posted by Ian Gooch. It really captured the true nature of sunshine and showers and as soon as I saw it I thought it would make a great blog post.
Before I explain what is happening and why, have a look at the video below.
6am – Clear and cold start
First thing in the morning at the start of the movie the sky is largely cloudless, with just a little bit of patchy low cloud in the distance. At 6am the temperature was just 6C with the sun low on the horizon and not much heating of the ground taking place.
9am – Cumulus clouds start to form
By mid-morning, the sun is now higher in the sky and it begins to heat the ground more readily. This in turn heats parcels of air just above it which then rise upwards and condense to form clouds.
Initially there are a few tufts of cloud skirting across the skyline, but by midday, the clouds are better formed into fully fledged cumulus. However, at this stage, they are not developed enough to produce showers as they are not very tall.
Midday onwards – Signs of cumulus congestus
From midday onwards the sun reaches its highest point in the sky and it’s during the afternoon that the greatest heating of the ground occurs. This causes parcels of air to rise quicker and faster, resulting in more developed clouds that reach higher up into the sky.
You’ll notice that the tops of the clouds start to resemble cauliflowers. At this point the clouds become towering cumulus or cumulus congestus and have the capability to produce showers.
5pm onwards – Clouds dissipate
By the end of the afternoon the sun is a lot lower in the sky and therefore the heating of the ground and the air above it diminishes. This means that parcels of air no longer rise as readily and cumulus clouds don’t form any more. If anything clouds tend to dissipate.
However, well developed clouds that have formed elsewhere can survive for longer and be blown across the sky. If you look in the distance at 6.30pm, there’s a cumulonimbus cloud with a huge anvil that invades the skyline.
This cumulonimbus cloud will have given some places a heavy downpour with even a rumble or two of thunder, but as with the other clouds, they will start to fade as the sun sets and the energy from the heating of ground fades.
So the next time you look out of your window and see the shower clouds drifting by, hopefully you’ll be able to think back to this blog and know how it all works!