The old saying is true: there is no such thing as a free lunch, especially when it comes to accepting a weather forecasting challenge from StatWeather, the Florida-based data vendor.

"What we've found is that some people are persuaded by the accuracy of our product by looking at the analytics and at the back-testing," says Ria Persad, the firm's co-founder and chief executive. "Other people who trade in the market are more experiential and they have to see it to believe it."

So the firm offered