.

It might be a long shot but shouldn't your ->

Storage::delete('/articles/150x150/'.$article->outside_image);

include your images directory? I mean you are referencing it in the location where you are saving it. As far as I am aware Storage is by default storage/app/public so when you say Storage it translates to storage/app/public/articles and not storage/app/public/images/articles where you saved it.