Tornado-spawning US storms seen from space
Recent days have seen the US experience its first significant tornado outbreak of 2014, with severe thunderstorms affecting an area from the Plains, through the Midwest and into the Carolinas.
This sudden burst of tornado activity comes just days after NOAA’s Storm Prediction Center announced that the US had its quietest start to the tornado season since detailed records began in 1953.
This year, up to 21 April, there had been only 20 tornadoes recorded, which is well below the average of 157 for that point in the season.
However, preliminary data from NOAA shows that there have been an estimated 36 tornadoes on 27-28 April, leading to around 29 fatalities.
These figures are likely to increase further when the data for 29 April is collated.
What causes tornadoes to form?
Tornadoes are spawned by violent, rotating thunderstorms that form due to warm, humid air from the south, colliding with cooler, drier air from the north.
The clash of air with big variations in temperature and humidity fuels super cell thunderstorms, that provide some of the most dangerous weather on the planet.
Although they can occur anywhere, tornadoes are most prevalent in tornado alley in the US, where the flat low-lying central plains offer an ideal breeding ground for severe storms to form and roam for mile after mile.
Statistics show that around 1,200 tornadoes affect the US each year, with peaks occurring along the Gulf coast earlier in spring, shifting to the southern plains from May to June, before reaching the northern plains and Midwest in June and July.
Tornado-spawning storms from space
The video below from NASA/NOAA GOES Project, shows satellite imagery on 27-28 April over the Plains and Midwest of the US.
If you watch closely, you can clearly see the moment that the severe thunderstorms erupt quickly and violently from the surface, reaching around 30,000ft into the sky – the height at which planes fly.
The collision of warm, humid air and colder, drier air creates a loaded gun set up in the atmosphere, where there’s a lot of potential energy building up.
When this energy is released, often triggered by rising daytime temperatures, it is the large-scale equivalent of taking the lid off a saucepan of cooking popcorn.
The risk of tornadoes will continue through the Mid-Atlantic and south eastern states of the US during Wednesday and Thursday, before the severe weather eases at the weekend.
I’ll be keeping an eye on the storms as they develop and posting updates on Twitter – @liamdutton