The NANOOS Visualization System (NVS): A Decade of Development and Progress Addressing Stakeholder Needs Craig M. Risien Oregon State University 104 CEOAS Administration Building Corvallis, OR 97331 craig.risien@oregonstate.edu Jan A. Newton University of Washington 616 NE Northlake Place Seattle, WA 98105 janewton@uw.edu Troy Tanner University of Washington 616 NE Northlake Place Seattle, WA 98105 troyt@apl.washington.edu P. Michael Kosro Oregon State University 104 CEOAS Administration Building Corvallis, OR 97331 mike.kosro@oregonstate.edu Emilio Mayorga University of Washington 616 NE Northlake Place Seattle, WA 98105 mayorga@apl.washington.edu Rachel Wold University of Washington 616 NE Northlake Place Seattle, WA 98105 rwold@uw.edu Jonathan C. Allan Oregon Department of Geology & Mineral Industries 313 SW 2nd, Suite D Newport OR 97365 jonathan.allan@oregon.gov Charles Seaton Oregon Health & Science University 3181 SW Sam Jackson Park Road Portland, OR 97239 seatonc@ohsu.edu Abstract— Over the past few decades coastal regions have experienced considerable socio-economic change. Accompanying these socio-economic shifts are unprecedented environmental changes, which include variation in magnitude and frequency of extreme weather events, marine heatwaves, increased ocean acidification, expansion of dead zones, extreme harmful algal blooms, and accelerating sea level rise. To understand these emerging environmental shifts, the past two decades have witnessed increased capacity to monitor changing environmental conditions and predict with greater accuracy such variations and events. These observation and prediction systems produce ever increasing amounts of data. Ongoing efforts to deliver this information using standard data models, metadata, data access protocols, and community accepted data server applications have helped reduce the heterogeneity of these data and improved data distribution. However, delivering critical information to stakeholders in a user-friendly and accessible manner remains a challenge. Beginning in 2009, the Northwest Association of Networked Ocean Observing Systems (NANOOS), the U.S. Integrated Ocean Observing System (IOOS) regional association for the Pacific Northwest, began to address this challenge by developing the NANOOS Visualization System (NVS), a map- based platform that aggregated a multitude of diverse data sets and forecast model fields into one system with the goal of delivering a more seamless, one-stop-shopping experience for users of coastal, ocean and atmospheric data. Here we describe the early vision and development of NVS and how it evolved into a flexible, multi-application platform where customized web applications can be developed to meet the needs of specific stakeholder groups. We focus on three applications (Seacast, Shellfish Growers, and Tsunami Evacuation Zones) that were developed using more formal design processes in close coordination with commercial crab fishermen, shellfish growers, and state and local emergency managers. In addition, we briefly describe the Tuna Fishers application, which evolved out of informal discussions with recreational tuna fishers. In highlighting these applications, we demonstrate the flexibility of NVS to quickly spin up prototype applications using pre-existing NVS framework elements. Working closely with small groups of dedicated stakeholders, we are then able to refine and extend an application before releasing it to the broader audience. Such a capability has enabled NANOOS to truly meet stakeholder needs, while increasing user capacity to understand and better respond to ongoing regional environmental changes. Keywords— NVS; NANOOS; Product development; Data visualization; Stakeholder engagement 978-0-578-57618-3 ©2019 MTS