、、。
Every time the wind blew, cherry blossom petals came fluttering down.
Literal
Wind [subject-が] blow [each-time-たびに], cherry blossom [genitive-の] petals [subject-が], fluttering [adverbial-と] were-dancing-down.
A seasonal scene built on two notable grammar points. (1) ~たびに ('each time X,' 'whenever X') attaches to a verb in dictionary form to mark a repeated trigger — here the wind's blowing triggers the falling. (2) ひらひら is an 擬態語 (state mimetic) for light, fluttering motion — petals, leaves, flags, thin cloth. It takes the adverbial particle と when modifying a verb, following the typical mimetic pattern. 舞い降りる is a compound verb: 舞う ('dance, flutter') + 降りる ('descend') = 'come fluttering down' — a vivid, slightly poetic verb used for petals, snow, birds. The ました form is missing its い (舞い降りてました, not 舞い降りていました) — a common casual contraction.