Hull moved up to 18th, level on 16 points with Crystal Palace above them, after fighting back from a dismal start when Junior Stanislas thumped Bournemouth ahead from the penalty spot after three minutes.
The lead lasted until the 31st minute when Hernandez, playing his first league game since November, timed his leap perfectly at the far post to head home Andrew Robertson's cross.
Having been outclassed in the early stages, Hull turned the match on its head in the second half, with Hernandez drilling them ahead left-footed and a Tyrone Mings own goal sealing the victory.
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(Reporting by Toby Davis; editing by Neil Robinson)
