Learn German: Wir warten darauf, dass sich der Wirbelsturm nähert. - We are waiting for the cyclone to approach.

The verb warten requires the preposition auf (to wait for). When you are waiting for an entire action described by a dass-clause, you can't just drop the preposition. Instead, you need a placeholder in the main clause to attach it to. That placeholder is the da-word darauf.

Why is the verb reflexive (sich nähert) when the English translation isn't?

The German verb for "to approach" or "to draw near" is sich nähern. It requires a reflexive pronoun in German, effectively meaning the storm is bringing itself closer. English often drops reflexive pronouns in cases where German strictly requires them.

Why is the reflexive pronoun sich placed right after dass, before the subject der Wirbelsturm?

In German subordinate clauses, pronouns like to be as close to the beginning of the clause as possible. When the subject is a full noun like der Wirbelsturm, a pronoun like sich usually slips in before it. While dass der Wirbelsturm sich nähert is also grammatically acceptable, putting sich first sounds very natural. (Note: If the subject were a pronoun, it would have to come first: dass er sich nähert).

How does the word Wirbelsturm break down?

It is a compound of der Wirbel (vortex, swirl, or whirl) and der Sturm (storm). It is the standard German umbrella term for cyclones, hurricanes, and typhoons.