The report above said it was coming from the South, and couldn't go East coz Norway, basically. Meanwhile, the usual flow of air was coming in from the West. So the depression carrying the storm got stuck.
Depressions rotate anti-clockwise, a bit like a big slow rainy wheel. If one becomes stationary, which is rare, the same rainy bit (sort of like a spiral spoke IYSWIM) arrives from the West, twirls round anti-clockwise via the South, and then comes back in from the East. This one was, to all intents and purposes, stationary over the British Isles for several days.
All the Environment Secretary had to do was to sit and watch the Met Office weather forecast animation, each day - it was hardly unambiguous! It didn't take long to watch it all, I know coz I did it myself
If something can't be put in a memo or on a single side of A4, in writing, it's too hard for many politicians to understand. PPE, unfortunately, has no science, maths or stats components (cynical
)