"The storm is picking up."
Translation:La tempête se lève.
Was that not accepted? I also thought them fairly synonymous.
Perhaps it is because "une tempête " is generally characterised by very strong wind, while "un orage " is characterised by thunder and lightning (between clouds or between clouds and the ground). (Ref: WordRef).
With that description in mind, as "se lever", in meteorological terms, is used to describe wind, I could only assume that this is the reason it is referring to une tempête.
Perhaps a native speaker could clarify this for us.
That means "The storm is nearly here" and indicates it hasn't yet arrived whereas "The storm is picking up" indicates that it has arrived and is intensifying.
"se leve" means "to rise", "to get up" and, in the sense of the wind, "to pick up".
"La tempête se lève" → "The storm is picking up"