Over the past few months we have experienced some weird weather in the UK, from flash floods and super-strong winds to storms with names, what exactly is going on? And more importantly, when will it end?
You may have heard of El Niño being to blame for our weather, but it isn’t new. The El Niño Southern Oscillation is a periodical change in climate sea surface temperature over the East Pacific Ocean. When the temperature is higher than normal, it is known as El Niño and when the temperature is lower than normal it is El Niña. Each period usually lasts 3-4 years and the current El Niño is the strongest recorded in the last 50 years.
A strong El Niño can have some odd effects on the world, from increased malaria to civil conflict escalations. Luckily, the UK is very far away from the East Pacific Ocean so is not directly affected by El Niño, but the knock on effects, combined with other weather systems do effect us. Typically, it is expected that El Niño would make Northern Europe drier and colder during winter, and Southern Europe wetter and milder. Yet so far, our winter seems to be far from dry as other factors have come into play.
El Niño caused a weaker hurricane system in Southern North Atlantic, resulting in higher ocean temperatures. With higher temperatures, the air can hold more moisture. This, combined with a stronger than normal jet stream, caused a storm of dense air to move towards the UK and release the moisture as heavy rainfall over Cumbria. This was known as Storm Desmond, it hit the UK in early December.
Hot on the heels of Desmond, Storm Frank arrived in late December. Opposite to the Southern North Atlantic, ocean temperatures in the Northern North Atlantic are colder than usual and so set up a strong temperature gradient, which strengthens the jet stream. This created a cyclone known as Storm Frank. This cyclone absorbed warm, moist air from the South, creating heavy rainfall and flooding across the UK.
High pressure to the East of the UK blocked the westerly jet from passing over the UK, this strengthened the southerly winds, allowing Storm Frank to bring warm air into the Arctic.
El Niño may not be the sole reason for the storms in the UK, but it is certainly a factor. Climate change is also exacerbating the problem, as with higher temperatures, more moisture can be held in the air. For every 1oC increase in temperature, the moisture content of the atmosphere increases by 6%, meaning heavier rain and flooding. It isn’t all bad news, the effects of El Niño in the UK are predicted to be stormy weather in the early winter but the risk of storms and heavy rain is set to decrease over the coming months, as things hopefully settle back to normal as the Southern North Atlantic cools a little.