Over the last few days, we have seen the arrival of hot and humid weather, with some thunderstorms. Various media outlets have associated these conditions with the arrival of what is termed a Spanish plume, which often leads to scorching temperatures and the risk of severe thunderstorms. This week we have had both in many parts of the country.
But what exactly is a Spanish plume and how does it affect our weather? The “plume” can build up when we have slack areas of low pressure to the west and high pressure to the east, drawing up a gentle southerly flow. This often originates from the elevated Spanish plateaux, hence the name.
As you might expect in summer, this brings hot and humid conditions, with temperatures sometimes well over 30C, which in turn leads to severe thunderstorms.
High temperatures and high moisture levels make for atmospheric instability which fuels storms. This set-up can also provide what is known as a “strong cap” to the atmosphere, preventing air from rising to form thunderstorms. However, with enough daytime heat, or a front moving in from the Atlantic, the cap can be broken, causing rapid thunderstorm development. A strong cap can mean storms are fewer in number, but greater in intensity.