Severe tornadoes hit the US this week, with at least seven reported on Tuesday in Illinois, while on Wednesday morning a powerful tornado tore through south-eastern Missouri causing widespread damage and at least five deaths in Bollinger County.
According to the National Weather Service, the Missouri tornado lasted about 15 minutes with winds reaching peaks of 130mph. A wave of thunderstorms and tornadoes in the US over the past few weeks have resulted in the deaths of at least 63 people.
Rising global temperatures and moisture levels are likely to make the conditions for the formation of severe storms more favourable, but that does not necessarily mean more tornadoes. It remains uncertain what will happen to wind shear – rapid changes in wind speed or direction – in a heating world, with some climate models indicating it will decrease in the future. Most tornadoes are generated from supercell thunderstorms, which are characterised by a continual rotating updraft, and develop in conditions of strong vertical wind shear.
Meanwhile, an unusually long period of La Niña has come to an end. Latest forecast models show that we will see a transition to the El Niño phase over the coming months, perhaps moving to moderate or strong El Niño conditions by late summer.
This shift will have significant implications for weather patterns across the globe. La Niña is often associated with more severe tropical storms across the Atlantic, greater precipitation across Australia and western parts of South America, as well an increase in hail and tornado activity across parts of the US.
In contrast, El Niño often leads to drought conditions and wildfires across Australia, stronger tropical storms across the Pacific, as well as an increase in average global temperatures.
A moderate to strong El Niño may have big implications for the weather pattern across Europe through the summer. Past El Niño years have seen unsettled conditions develop in north-west Europe in July, including the UK, with drier and hotter conditions focused across central Europe.
