Surprisingly quiet US tornado season gets under way

At least one person is confirmed dead after a series of tornadoes swept through the US state of Oklahoma.

One twister touched down in Moore, the town that was flattened in 2013 by the most violent of tornadoes, an F-5 on the universally used Enhanced Fujita Scale.

In Sand Springs, a tornado warning was issued and sirens blared. Electricity supply transformers exploded and lit up the darkened sky, as heavy rain and hail the size of golf balls spewed from the storm’s churning base.

Violent wind toppled a radio station’s transmission aerial and flattened a mobile home park, killing one man.

Interstate highway 35 was shut after an articulated lorry was blown across several lanes.

In a normal spring, we would be counting thunderstorm super-cells, and their tornado offspring, by the dozen.

This should be ‘tornado season’ in the Plains States. So far this year it has been surprisingly, and pleasingly, quiet.

A waterspout, seen over Bull Shoals in Arkansas on Tuesday evening, is most likely the first tornado in the US this March.

At the time of writing, seven tornadoes have been counted this month in the whole of the US. The average for a normal March is 80.

This may be an unusually quiet tornado season, but natural variability is part of the weather pattern.

Recent studies, however, have shown a trend towards fewer days each year with tornadoes. Unfortunately, each of those days has more, and bigger, tornadoes.

This apparently slow start to the tornado season is, therefore, no indication of the rest of the year.

Closely clustered, more violent twisters seem increasingly likely with every passing year.