One of the great things about crowd sourcing is that we have the luxury of using numerous classifications to determine an answer for one image. The responses of 15 citizen scientists is much more powerful than a response from one person, even if that person is an expert.
We have gone through every single storm image on Cyclone Center that has been classified by at least 10 citizen scientists. All classifications were used to determine the variance of the image – or, how similar one classification was to the others. Ambiguous cloud patterns will have a higher variance than one with a clear eye, for example.