JQuery :: Insert Title Tag Into Hyperlinks Using Attribute?

I'm wanting to take all links pointing to external urls and insert a title tag with some text that I can then turn into a mouseover tooltip effect.The purpose is simple, we want to inform the visitor that by clicking on the link they would be taken away to another site. The warning message would be in the title tag.

Each external hyperlink already has an rel="external" tag so I can work off of that. This gives me:

$(document).ready(function() {
$('a[rel="external"])
});

As my element identifier. Now, in trying to insert this title tag, i've explored the append and appendTo but those refer to adding items to the end. I need the method that inserts this in between the <a></a> tags as it's own part of the hyperlink code. which method I should use to add something like this:

title="Clicking this link will take you away from this site"

I've even thought of possibly appending it as a hidden <span> item then revealing it on the mouseover.

One bit of additional info, i'm using Wordpress and want this to automatically deploy on all specified elements automatically.