Well, I dug up the site I was referring to....

This is all that I could really find about Harad, more specifically near Harad (as neither far Harad, nor the peoples inhabiting it, were ever described in any great detail in any of Tolkien's works).

Quote Originally Posted by Encyclopedia of Arda

An indefinite region that lay to the south of Gondor and Mordor, beyond the River Harnen. Little is said of it in the histories of Middle-earth, except that the Men of that land conspired with those of Khand, and with the Wainriders, to overthrow Gondor in the time of King Ondoher. The Gondorians anticipated their strike, and Ondoher created a Southern Army to defend his land against them. That Southern Army, under the command of Eärnil, met the invading Men of Near Harad in South Ithilien, and defeated them completely.
Not really much there as to the exact sites this place could have represented, if any....

....and Umbar....

Quote Originally Posted by Encyclopedia of Arda

A cape in the far south of Middle-earth, long held by Black Númenóreans, but conquered by Gondor for a time during the Third Age.

Notes 1 The name appears to contain the word mbar, 'home' or 'dwelling-place', an element seen fairly frequently in place names like 'Brithombar' or 'Dimbar'. The 'u-' prefix is hard to decipher, but it would normally form a negative, so perhaps 'Umbar' simply means 'not home' or 'away from home' (to the Númenóreans or Gondorians, that is). However, there is no definite support for this theory in Tolkien's works.

Umbar is also known to be the Elvish word for 'fate'. This seems an odd source for a placename, and is probably mere coincidence, but it may possibly refer to the fateful landing of Ar-Pharazôn here in the year II 3261, which ultimately led to the Downfall of Númenor.
So it seems that, although this place sounds very similiar to Ubar, it may well have had other meanings (Such as meaning "not home" or it being the elvish word for 'fate' coinciding with the place which was the beginning of the end for Numenor (which, if you know anything about Tolkien history, was supposedly a nation unmatched in power and beauty before it was cast into the sea by the gods, which is suprisingly similar to the legend of Atlantis).

Tolkien was trying to create a british mythology which was as rich as greek mythology, so I think he pulled aspects from all parts of his world....real life, legends and myths, his own imagination, etc.

The site can be found here if you're interested. It's quite good.