Where is Numenor located in Unfinished Tales: The Lost Lore of Middle-earth?

Numenor is an island in the Great Sea, separate enough from Middle-earth to make the trip between the two long and inconvenient, yet close to Middle-earth in that it is settled by Men and Eldar from there, and there is a great friendship and alliance for many centuries between the Rulers of Numenor and Gil-galad on Middle-earth. Numenor is described as a "Land of Gift". As a separate area from Middle-earth, far away and with no nearby enemies, it seems impregnable. Eventually, however, it comes under the influence of a vague "Shadow", and it sinks into the sea. Much of its history is forgotten and its lore is lost, except what was written down and kept in Gondor.