A Forecast Should Show a Range of Possibilities, Not Just One Number

It is easy to present tomorrow's weather as one precise number, but forecasts contain uncertainty. Multiple ensemble members help reveal a range of possible outcomes. That range is not decoration; it is part of the decision context.

Imagine two forecasts with the same average rainfall. In one, the ensemble members cluster tightly. In the other, they spread widely. The averages are identical, but confidence in the decision should not be. At the same time, ensemble spread should not be treated as a perfect measurement of every form of uncertainty.

The useful interface depends on the decision being made. Delaying work, preparing resources, or waiting for more information carry different costs, so uncertainty matters differently in each case. A probability without time and location context can still be difficult to act on.

I prefer forecasts that make fewer claims of certainty than the evidence supports. Showing a range is not avoiding responsibility. It is placing the strength and the limits of the available information in the same view.

Source: official reference.