Wednesday, 14 January 2004: 1:45 PM
Computing the odds on a good probability forecast
Room 6A
Operational weather forecasting contributed to significant advances in our
understanding of statistics towards the end of the nineteenth century, and
then to our understanding of dynamical systems towards the end of the
twentieth. It is now widely accepted that uncertainty in the initial state
of the atmosphere makes the hope of a single 'accurate' medium-range
forecast unobtainable, motivating operational ensemble forecasts.
Information from ensemble forecasts is crucial both for extracting the
socio-economic value that has justified operational forecasts since those
made by Fitzroy and for the empirical connection to the atmosphere that
turns model simulations into weather forecasts. It is less widely
accepted, but equally certain, that model inadequacy (errors in the
details of any model) will prevent accurate, accountable probability
forecasts. The implications this fact holds for both users and modellers
is explored. The more common foundations objective probability theory are
are based upon the notion of equally likely events; this is lost outside
the perfect model scenario. Consideration of the evaluation and use of
probability forecasts suggests the development of a truly multi-model
framework (as opposed to a 'best model' framework) and an alternative
approach to defining 'fair odds' in the context of risk management (as the
"implied probabilities" corresponding at a set of odds need not sum to
one).
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