sKILLy xplains da wishy washiness

Dear Tom,
What does a 30 percent chance of rain mean?
-Magee Amethyst

Dear Magee,

The percent chance (or probability) of rain is the forecaster's way of expressing how certain he is that it will rain. Ideally, a forecaster wouldprefer to issue a zero-percent forecast (it absolutely will not rain) or a 100-percent forecast (it absolutely will rain), but the present "state of the art" does not give forecasters that ability.

The proper interpretation of a 30 percent chance of rain (assuming the forecasts verify perfectly) is that you will have rain on your head three out of ten times that you hear such a forecast.

Please note that the percent chance of rain does not address the duration of rainfall (it might rain all day or only a few minutes) or the amount of rainthat comes down (unless the forecaster uses a qualifying term such as"heavy" or "light").

Anyone keeping a running count of how often they're right or wrong and how it compares to dem percentages dey use? Smiff?