After years of development, Weather Underground replaces NWS forecasts with their own prediction algorithm that incorporates tens of thousands of personal weather stations – like my dad’s – into its forecasts. The algorithm is called BestCast™. The press release talks about 42,000 stations, but I suspect that actual number is a bit less. Wunderground came up with this figuring by summing the total number of stations from each of three different data sets, however a number of stations actually send data to many different sources. For example, thanks to wview, my dad’s station sends to directly to Weather Underground and to the National Weather Service’s MADIS program via CWOP.

Another thing that’s new on (or at least I never paid much attention to it before) is if you scroll down to the “Forecast” section for a location they publish the RMSE for this location both their forecast and the NWS forecast. As a data guy, I find that transparency absolutely wonderful. Also, they link to the predicted hour-by-hour weather for a location (I suspect this is using an NWS model, since it’s reporting for an airport.), and the NWS’s “Area forecast discussion”, which is a conversational and wonky forecast. Personally, I like how it discusses how different models agree or disagree.