1 - could by city heat effect being normally warmer than the surrounding countryside could this affect (not sure if this is the right word?) into the sea?
2 - can features such as big piers, cliffs ( e.g.Tynemouth priory sits on?) deflect surface wind up vertically into the air?
3 - A flock of seagulls flapping their wings
I am just making total random guesses, I think at the end of the day its just pot luck