What was the reason for the tornado that hit London in 1021?

It even caused London Bridge to fall down.

https://www.historic-uk.com/HistoryUK/HistoryofEngland/Great-London-Tornado-1091/

nostr:nevent1qqs0p4l9e2k66fsdywrlltyrz73m2zwfl8tl99ryl47w3ctauu9xngcpz3mhxue69uhhyetvv9ujuerpd46hxtnfdupzp6s5tkrh7q3k3d3uhgp4wr0wq7c73q886kxrsce9gtth7hefgqc2qvzqqqqqqy442ck0 

 Sorry, 1091.