Economic development, increasing population, lifestyle changes, climate change, and underlying policies exert stress on both natural resources and aging infrastructure. Given the cost and timescales required to invest in new infrastructure (e.g., reservoirs, power systems), managing existing infrastructure better is critical. Further, in developing countries, limited institutional capacity is in place to mitigate environmental hazards which require significant coordination and preplanning among agencies. Hence, to improve disaster preparedness and infrastructure management against hydroclimatic extremes, this AccelNet project brings together national and international subseasonal-to-seasonal (S2S) forecasting agencies and sectoral agencies associated with water, power, and public health to accelerate the uptake of S2S forecasts forecast applications and services (FAS). Towards this, we will build a network of networks (NoN), S2S AccelNet, with 10 core partners and 13 collaborating institutions across the US, Africa, Brazil, and India to reduce societal vulnerability to climate, environmental hazards, and health risks. The rationale is to reduce critical gaps in FAS, incorporate FAS in regional climate outlook forums (RCOFs) and develop an interdisciplinary curriculum and workforce focusing on climate-informed adaptive management for various services.<br/><br/>The key objectives of the S2S-AccelNet project are to: 1) identify grand FAS research opportunities and challenges in FAS data availability and models, and policy issues; 2) recommend potential pilot basins/regions for FAS modeling, research and synthesis; 3) develop an open-source platform and knowledge base — S2S-AccelNet Hub — for better researcher-stakeholder engagement; and 4) execute interdisciplinary outreach and early-career exchange programs with 10 core and other collaborating networks and educational institutions. The intellectual merit of this project is towards building S2S-AccelNet Hub with pilot applications, which will promote convergent research on S2S FAS, together with improved strategies and knowledge for rapid sectoral uptake. By integrating forecasts, application-specific databases and models in a single open source platform, S2S AccelNet Hub, we will promote implementation of resilient and adaptive management policies. Evaluations of policy and institutional settings that aid or limit the application of S2S predictions will provide insights for forecast developers to customize the forecasts for better outreach in RCOFs. Successful FAS pilot projects will also promote strengthening industry-university partnership and lay the foundation for accelerating FAS research. The broader impacts of this project stem from interactions and exchanges across the NoN in enhancing the outreach and capacity building of major international forecasting institutions and agencies for active engagement with local/regional sectoral agencies. The databases and models developed through the S2S-Application Hub will promote strong collaborative and synthesis activities. Innovative professional training and mentoring plans such as annual symposia and 3-Minute Thesis presentations with participating universities will improve graduate students’ communication in interdisciplinary settings. Finally, key decision-makers could rely on the improved S2S forecasts and knowledge exchange through the FAS projects and S2S-AccelNet Hub for informed policy-making to develop S2S hydroclimatic forecast based adaptive management strategies that meet the UN’s Sustainable Development Goals.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.