Inspired by the extreme weather patterns around the globe that have been seen this week, we take a look at how a storm actually becomes a storm – with the help of some stunning weather patterns seen first- hand from flight deck.
Thunderstorms are formed from damp, warm air rising within an unstable air mass. Some find them exciting and some find them terrifying. But there is no doubt that if you are in an aircraft, you will want to avoid them.
The birth of a storm begins with cumulus cloud ‘growing’ or ‘towering’.
Cumulus Cloud: "puffy", "cotton-like" or "fluffy" in appearance, and have flat bases.
The warm, moist air from the surface of the earth rises as it has a lower density (lighter) than the cold air above it. The rising air cools to a temperature known as the ‘dew point’, this is the temperature at which the air becomes saturated with water, and condenses.
But, as the old saying goes, you can’t stop hot air from rising! Condensing is a warming process so it keeps the air inside the cloud warmer than the surrounding air, so it might continue to rise.
How quickly the air rises decides how intense the storm will be. It depends on:
Eventually the upward draughts of air will not be strong enough to suspend the water and ice within the clouds, at this point it will begin to fall. When you combine that with the edges of the clouds cooling, downward draughts of air are created. This signals the next stage in the storm.
This is the storms most intense state; it has both up draughts and down draughts. At this stage, you may be able to see the cloud reach a point where it cannot rise any higher and the temperature of the atmosphere stops falling. This is known as the tropopause and is visible when the cumulus clouds form an anvil shape.
This picture taken on a flight between London Luton and Rome Fiumicino indicates just that. The mature stage of a storm is most the most likely time to see thunder, lightning and hail produced. Precipitation (water) will start to fall and gusts will start to appear below the storm.
In the final stage the upward draughts that were previously the stronger force are now dominated by the downward draughts. The upward force weakens as downward travelling gusts move further away from the storm and often overpower any new warm air that tries to rise. During this stage the remaining water droplets and ice crystals will fall until the cloud eventually completely disappears. The storm is over!
These are lines of thunderstorms that usually occur ahead of a cold front, i.e. an advancing mass of cold air.