Measuring the winds that can snap a tree in half
HOW strong does the wind have to be to snap a tree in half? If you thought, lying awake in your bed this week and listening to the gales ripping across your garden, that it was purely down to bad luck, then think again. For centuries some of our greatest brains, Leonardo da Vinci and Galileo among them, have directed their energies to coming up with an exact answer.
The most recent figure for what is called “stem lodging” was produced in a study by the Ecole Polytechnique in France in 2016. It settled on 90mph (145kmph) as breaking point, for all sorts of complicated mathematical reasons, and said it was irrespective of tree’s size, or whether it was hardwood or softwood.
Which means our trees should have been safe last week as Wednesday turned into Thursday and the wind was buffeting much of the UK. The highest wind speed recorded was 83mph at Tibenham Airfield in Norfolk.
However, the fact that there were plenty of upended trees blocking roads and rails the next morning – Lincolnshire police alone reported 80 – means that either this latest calculation is wrong, or that the debris was a case not of “stem lodging” but rather of “root lodging”. This happens when a tree is toppled by wind that tears its roots out of the ground.
If all this is too much in the midst of a cold snap, which has seen thick snow in Scotland, Northern Ireland and northern England, then at least this weekend is pretty straightforward: good today and bad tomorrow.
The winds and downpours of recent days will abate this morning, though southern England could have some sleet. Elsewhere, expect drier, calmer conditions, with the best temperatures in the south west. By tomorrow, the rain and breeze will return. In northeast England and eastern Scotland, that rain may turn into snow.