Learn Farsi: باید در این پناهگاه اضطراری بمانیم تا طوفان تمام شود. - We must stay in this emergency shelter until the storm ends.

Because of the word tâ (until). When tâ introduces a future boundary or a condition that hasn't happened yet, like waiting for a storm to end, the verb that follows it must be in the present subjunctive.

Why is the first verb, bemânim, also in the subjunctive?

It is triggered by the word bâyad (must) at the beginning of the sentence. Remember that modal verbs like bâyad require the main verb of their clause to take the subjunctive form.

Could we use tâ inke instead of just tâ in this sentence?

Yes, you can use tâ inke interchangeably with tâ here to mean until. Using tâ inke sometimes adds a slight emphasis to the wait, but the meaning and the grammar rule requiring the subjunctive verb remain exactly the same.

How does the word panâh-gâh break down?

It combines panâh, meaning refuge or shelter, with the suffix -gâh, which denotes a physical location. So panâh-gâh literally translates to place of refuge.