We obviously can't speak to the ANA (and partner?) awards policy for times like this, but we had something similar in Hong Kong in early June, 2017. There was a typhoon barreling straight at HKG. Then we got a note slipped under our hotel room door alerting us to it (in case we had been hiding in a cave somewhere!?).
And THEN... the Typhoon was upgraded to Category 8, which was apparently right at the top of the scale (it was a bit hard for us to get that exact, but we certainly got the main point).

We were on CX F, which doesn't have a lot of seats (as in only 6 per flight), so we were quite worried about IF our flight was cancelled, how long would it be before *2* F seats were open again, with only 1 flight per day nonstop to our destination.

Our tickets were with AAdvantage miles, booked directly with AA, not CX.
But at the last minute that evening, as the weather looked more dire, we called CX (note, not AA) and asked them if we could switch to one day early, and leave in the morning.

"No problem" was the answer, and we changed reservations, albeit not particularly looking forward to taking off into an arriving typhoon. (For whatever reason, though we are accustomed to "Hurricanes", "Typhoon" sounded *much* more ominous!)

As it turned out, there was very heavy rain, and the ride to the airport was slow... but our take-off was on time, and remarkably smooth as well.
I don't think a "Category 8" Typhoon actually "hit" HKG directly, and we probably should have stayed. After all, we DID have travel insurance, so they would have kept us at the Peninsula for a few more nights if necessary.
However, I don't know how long they'd do that if the only reason was "airport open, but we want to wait for F availability during prime travel season"

Point is, CX allowed us to change our AAdvantage-issued tickets, and at zero charge, given the weather circumstances.

Good luck!

GC