Is it a condition to verbally express the intention when intending an 'Umrah on behalf of a deceased person, such as by saying: "Here I am, Allah, for an 'Umrah on behalf of my grandfather"?

It is permissible to perform Hajj or Umrah on behalf of another, provided that the person performing the Hajj or Umrah has already performed the ritual for himself. The intention for the person on whose behalf Hajj or Umrah is being performed is sufficient, and it is not required to mention their name or utter it, although it is better for him to say, at the first talbiyah: "Labbayk Allahumma an [so-and-so]."