Principle: Providing the evidential basis for all estimates
The evidential basis for estimates of any sort should always be provided when estimates are given. This is so that anyone using such estimates can assess their likely accuracy. Failing to give such estimates exposes decision-makers to the risk of thinking that the estimates they have been given are more accurate than they actually are.
The graph below  conforms with this principle. The predictions (‘forecast’) are visually differentiated from the actual empirically derived data (‘actual’) regarding what has happened. This way of presenting estimates versus empirically derived data is consistent with the principle above. The website also contains more detailed notes on how the forecasts estimates were derived.
 Metservice website accessed 9 Jan 2013at http://www.metservice.com/