Predicting rainy seasons: quantifying the beliefs of prophets

Abstract

In general, meteorologists find it difficult to make seasonal predictions in the north-east region of Brazil due to the contrasting atmospheric phenomena that take place there. The rain prophets claim to be able to predict the seasonal weather by observing the behavior of nature. Their predictions have a strong degree of subjectivity; this makes science (especially meteorology) disregard these predictions, which could be a relevant source of information for prediction models. In this article, we regard the prophets’ knowledge from a subjectivist point of view: we apply elicitation of expert knowledge techniques to extract their opinions and convert them into probability densities that represent their predictions of forthcoming rainy seasons.

Keywords:

• Brazilian climate
• elicitation
• Kumaraswamy distribution
• rain prophets
• seasonal weather

Acknowledgements

We thank Helder Cortez for helping us with the structure for the interviews, Renzo Taddei for the helpful information about the prophets, and the 30 prophets who agreed to give up their own time to participate in this study. We would also like to thank the anonymous referees for their helpful comments on an earlier draft of this paper.