Insights into the Usefulness of a New Extreme Weather Guidance Tool The Long-Range Tropical Cyclone Outlook for the Southwest Pacific (TCO-SP)

Tropical cyclones (TCs) produce extreme winds, large waves, storm surges, intense rainfall, and flooding and account for almost 75% of natural disasters across the southwest Pacific (SWP) region. The island nations and territories across the SWP rely on seasonal TC outlooks for insights into possible risks for the coming TC season. Launched in July 2020, the Long-Range Tropical Cyclone Outlook for the Southwest Pacific (TCO-SP) provides deterministic (frequency) and probabilistic (likelihood) TC outlooks for 12 subregional and island-scale locations up to 4 months (July) before the start of the SWP TC season (November–April). Following TCO-SP’s first season of operation, this study (i) outlines the process of generating and communicating TCO-SP outlooks, (ii) provides a postseason validation of TCO-SP performance on the 2020/21 SWP TC season, and (iii) reports on the results of a questionnaire used to determine end-user needs and user-perceived usefulness of TCO-SP. Postseason validation indicates that TCO-SP successfully predicted a near-normal SWP TC season. Island- and regional-scale guidance also performed well, with an average skill score of 54% across all regions. Analysis of responses to a TCO-SP questionnaire revealed a diverse and global user base that indicate the core features of TCO-SP (island-scale/regional-scale outlooks, regular monthly updates, and an outlook lead time up to 4 months before the start of the TC season) are particularly useful. TCO-SP will continue to innovate to deliver reliable and trusted TC outlooks with a goal to reduce disaster risk and increase resilience across the SWP region.