Enhancing Climate Resilience in Pacific Island Countries: Integrating Impact-Based Forecasting into the PICASO

Pacific Island Countries (PICs) are exceptionally vulnerable to climate variability and extremes, which pose direct and increasingly severe threats to critical socioeconomic sectors. To address these urgent challenges, the Pacific Island Countries Advanced Seasonal Outlook (PICASO) system was developed. PICASO is an advanced hybrid seasonal prediction system that strategically integrates the strengths of both statistical and dynamical models to produce reliable, high-resolution climate information. Based on the APEC Climate Center Multi-Model Ensemble (APCC-MME), the platform provides user-friendly, high-quality climate predictions that are specifically tailored to individual observational stations within the region.

This study provides a comprehensive introduction to the PICASO system, detailing its sophisticated hybrid technical framework and foundational climate services. Furthermore, it introduces the recent development and integration of impact-based forecasting (IBF). This evolution represents a significant enhancement designed to bridge the critical gap between standard climate data and actionable, sector-specific guidance. We detail new content within PICASO that has been co-developed with national stakeholders to address specific local vulnerabilities.

Key implementation examples include:

• Niue: Wildfire risk assessments based on projected dryness and weather conditions. 
• Marshall Islands and Tuvalu: Drought forecast. 
• Palau: Forecast for dam water levels to support water resource management decisions. 
• Cook Islands: Integrated monitoring and outlooks for sustainable water resource availability. 

This transition from general climate outlooks to impact-based forecasting empowers Pacific stakeholders to shift from reactive responses to a proactive adaptation posture, substantially strengthening regional resilience against climate-related risks.

Key words: Seasonal climate forecasts, hybrid seasonal prediction system, PICASO, Pacific Island Countries, impact-based forecast 

※ This work was supported GCF-UNEP CIS-PaC5 Project.