... how powerful are jet engines? I remember seeing where it was said that the blast is like hurricane strength winds and can cause considerable damage. Are we looking at winds of more than 120mph? Could the blast uproot trees or damage houses?
On a civil large bypass turbofan engine, the core flow exit velocity at full power will be circa 200 metres per second, which is circa 450 mph. If Barit1's friend was driving 100 yards behind a big fan engine, the blast he felt would have taken only half a second to travel that distance. So, yes, they are damned powerful. Obviously, bypass flow is significantly slower.
There are a number of 'training' videos around to demonstrate the power of these engines to airside workers. They usually take the form of some car or truck passing behind the aircraft and being blown away by the blast.
At Filton, they have a traffic light system on the A38 where it passes the end of the runway to stop traffic if there's something big sitting waiting to go for this very reason.