Monday, September 12, 2016

How to interpret the weather forecast

Someone wrote: "When a weather forecaster tells me the probability of rain tomorrow is 50%, I translate it as “I don’t know.”"

I translate the weather forecaster as saying "Out of a 100 days where the forecast is 50% probability of rain, it rains on 50 of them".

Is this the same as "I don't know"?

Some possibly relevant information:  where I live it rains on the average on 117 days of the year.   In Arizona, it rains on the average on 36 days of the year.  Honolulu, Hawaii has rain on 154 days of the year.

With the above examples, I think the forecast of "the probability of rain tomorrow is 50%" is the closest to "I don't know" in Honolulu, and the furthest away from "I don't know" in Arizona.   I haven't done any Bayesian calculations or anything, just working from intuition.

What do you think?