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© Crown copyright Met Office
Uncertain ForecastPeter GibbsBroadcast meteorologist, BBC and Met Office
Obstacles and AssumptionsWhy are we not communicating it already?
• …the public don’t understand probabilities…
• …uncertainty is too difficult to communicate…
• …the Press don’t get it…
• …the Met Office (or BBC) is just covering itself…
• …you can’t say 50% chance - that is admitting defeat…
• …just tell me what will happen…I just need to make a decision…
• or is that “just make my decision for me” ?
© Crown copyright Met Office
Storm of 16th Dec 2011
© Crown copyright Met Office Ensemble Training 2012
5-day forecastBoth EPSs flag small risk exceptional low over UK
EC 944MOGREPS 938
© Crown copyright Met Office Ensemble Training 2012
Forecasters communicate low risk of very high impact
• BBC shows two alternative tracks:
• Track 1 is low probability but highest impact (severe gales and heavy snow).
• Track 2 has a higher probability but lower impact (some snow, but lighter winds).
© Crown copyright Met Office Montreal Workshop, March 2012
Max Temp uncertainty 1-5 Feb 2012
• Cold block over Europe
• Frontal system approaching from Atlantic
• Uncertainty about progression
BBC Graphic
presentation
© Crown copyright Met Office
Decision-making with Uncertainty
• There is always uncertainty in forecasts
• Recent study in US showed that where uncertainty is not shown, people make own assumptions (Joslyn et al, 2011)
• Often over-estimate uncertainty
• By explicitly providing uncertainty, people make better decisions
• …
© Crown copyright Met Office
Addressing assumptions:“the public don’t understand uncertainty”
“uncertainty is too difficult to communicate”
• Do ensemble forecasts cause confusion?
• Can players make better decisions using ensemble forecasts?
• How does this vary with presentation type?
• Demographic influences
Randomised design
Collected basic demographic data
Outcomes generated on-the-fly (based on probabilities)
Ability to separate 1st time players
© Crown copyright Met Office
Playing the game
How confident are you about each shift – tests ability to assess probability from presentation
Choose location or shift – tests ability to understand relative probability from presentation
© Crown copyright Met Office
Scoring
• Each shift is allocated an outcome randomly selected from the forecast distribution
• Element of luck!
• Amount of ice cream bought and sold depends on advice and outcome
• Total score at end of game:
© Crown copyright Met Office
Weather Game – “Engaging online users to gather feedback on the best way to represent forecast uncertainty”
-11,000 responses – Largest meteorological survey of its kind
-Collaboration with UK Universities – Bristol & Cambridge
-Showed that people make better decisions when presented with uncertainty
- Consistent across all age groups and educational levels
- People made best decisions with the most complex presentations
Courtesy of Liz Stephens