@jaredfood If it is anything like te reo Maori then I think the "He" is more of a time marker than the verb "is". I think of it as "Presently" when I see it in a sentence. So in this case, it might be enought to say Short (modifier) his mother (noun/subject). Or as some people mentioned, short = his mother. Which is eerily like the copula in Irish.
Update: I'm wrong.
This dictionary says it's an indefinate article, like 'a' or 'an,' as in an apple. http://wehewehe.org
Therefore, 'He Pōkole kona makuahine." would be clunky in English. It would be, His mother is a calm. (I think).