IPA: /ˌɒpəˈtjuːnli/
KK: /ˈɑːpərˌtunli/
In a way that is suitable or beneficial at a specific time.
She arrived at the meeting opportunely, just as the discussion was starting.
Opportunely is formed from "opportunus" (from Latin, meaning favorable or suitable) and the suffix "-ly" (meaning in a manner). The word describes something that occurs in a favorable or suitable manner, especially at the right time.
Think of 'favorable' ('opportunus') to remember that 'opportunely' means something happening in a suitable or timely way.