I'm not really a convertible guy because my hair is getting a little thin up top and I'm afraid of getting sun burned!
That looks like it could be a problem with the door glass though. Sometimes it gets out of alignment and doesn't fit flush with the weatherstripping.
And I think that the door glass on a convertible has to clear the convertible top, so it is different than the coupes.
Check to see if the glass looks like it is even all of the way around where it meets the weatherstripping, when the window is all of the way up.