  The spread of ensemble weather forecasts contains information about the
spread of possible future weather scenarios. But how much information does it
contain, and how useful is that information in predicting the probabilities of
future temperatures? One traditional answer to this question is to calculate
the spread-skill correlation. We discuss the spread-skill correlation and how
it interacts with some simple calibration schemes. We then point out why it is
not, in fact, a useful measure for the amount of information in the ensemble
spread, and discuss a number of other measures that are more useful.
