Barcelona?
I wonder if that referred to an earlier sector operated by the aircraft? Your incoming flight left Gatwick 4hrs 38 late and went nowhere near Barcelona. It followed the usual track to Lisbon, a straight line - overhead the Channel Is., Brest Peninsula, Bay of Biscay and on into Lisbon.
I noticed that a number of TAP flights, that evening suffered severe delays of between 1 and 4 hours (both arriving and departing) but their flight from Heathrow arrived on time as did BA 504 from LHR. Your inbound flight was followed by another, on time, EZ arrival from Manchester.
There does not seem to have been any weather disruption at Lisbon, save for some pretty sporty gusts late afternoon