Can you still play riposte for the + might if mel awakened is empowered?

Yes — you can still play Riposte targeting a spell protected by an Empowered Mel, and you still get the +Might.

A spell that "can't be countered" is still a legal target for Riposte; the prevention only stops the counter action, not the targeting (Rule 358.3.a — the counter is skipped as an impossible instruction on resolution). Riposte's +Might is a separate instruction from the counter, so it resolves normally and your unit still gets +[M] equal to the spell's printed Energy cost this turn — while the protected spell resolves as if nothing happened. Note this only matters if the spell on the chain is Mel's controller's own spell; if it's the opponent's spell, Mel's protection doesn't apply and Riposte counters it normally.