Corbyn's predictions work best when they cover a wide area, are broad in scope and track seasonably predictable events. He likes to focus on the places where his predictions work rather than where thy fail.
He has also failed to publish the techniques he uses so they are not available for independent scientific scrutiny. Piers Corbyn certainly has notoriety but not "fame". If he published his methods and was able to show that they worked consistently he might gain fame.
