weep, ah, alas
嗚 centers on vocal expressions of sorrow or exclamation: weeping, or crying out with sounds like "ah" or "alas."
嗚 combines 口 (mouth) with 烏, which likely contributes the sound and may suggest a bird-like cry, together expressing vocal exclamation or weeping.
A mouth 口 beside a crow 烏: imagine a crow's harsh caw as a sad cry, like someone weeping or sighing "ah, alas."
For ウ, picture a person weeping and letting out a long "oooh" sound: oooh -> ウ, like a mournful cry from the mouth.