Impact-based forecasting in South East Asia – what underlies impact perceptions?

The move towards impact-based forecasting presents a challenge for forecasters, who must combine information not just on what the weather might be, but also on what the weather might do. Yet different hazards and impacts are qualitatively distinct, meaning such information cannot be easily or straightforwardly integrated. The present study aimed to provide a way of characterising seemingly disparate impacts. In a collaboration between UK psychologists and partners from three meteorological organisations in Indonesia, Malaysia and the Philippines, the psychometric paradigm was employed to investigate how forecasters and stakeholders perceive weather-related impacts. Participants provided ratings of nine categories of impacts on a total of 10 characteristics, as well as providing an overall impact severity rating. Principal components analysis revealed differing component solutions across countries, which explained around 75% of the variance in perceptions. There were some similarities across all countries, with the characteristics ‘worry’ and ‘destructiveness’ loading positively together, as well as ‘likelihood of harm’ and ‘seriousness of harm’. We did not find strong evidence to indicate that forecasters and stakeholders perceive impacts in different ways. Our results highlight the complex nature of impact perceptions, which are characterised not just by objective factors such as impact scope and duration, but also subjective factors, such as worry and perceived severity

Investigating the decision thresholds for impact-based warnings in South East Asia

The move towards impact-based forecasting presents a challenge for forecasters, who must combine information not just on what the weather might be, but also on what the weather might do. Such forecasts require an integration of both likelihood and impact severity information to issue a particular weather warning. The current pre-registered study focusses on forecasters' and stakeholders’ thresholds for determining the level of impact-based warnings, set in an area of the world particularly susceptible to extreme weather events. Set in the context of one hazard (heavy rainfall or river flooding), forecasters and stakeholders from Indonesia, Malaysia and the Philippines provided hypothetical impact-based warnings for impacts of varying likelihood. Results indicated generally good alignment with the warnings implied by previously developed impact tables. In the one country where a comparison was possible (the Philippines), we did not find evidence to suggest that forecasters and stakeholders use different thresholds for issuing warnings. We suggest that warning thresholds should be subject to regular monitoring wherever in the world an impact-based approach is used