The First Session of the Commission for Instruments and Methods of Observations (CIMO), Inter-Programme Expert Team on Operational Weather Radars (IPET-OWR) was held over 13 to 16 March, 2017, at the Japan Meteorological Agency (JMA) headquarters in Tokyo, Japan. The session was kindly hosted by JMA and generously supported by Japan. The meeting was opened by the Director-General of the Japan Meteorological Agency, Dr Toshihiko Hashida, who highlighted Japan’s ongoing engagement in international operational weather radar activities, collaboration and capacity development. The session was chaired by Chairperson of the IPET-OWR, Mr Daniel Michelson, Canada, who emphasised that the weather radar observing system was emerging as a global resource and that the team might be considered the stewards of this process under WMO and its technical commissions. The meeting informed team members and participants of the reasons for the formation of the team within CIMO under the joint management of CIMO and CBS at the behest of WMO Congress and its role in providing the WMO focus for international coordination of activities on operational weather radar systems as an important component of the WMO Integrated Global Observing System (WIGOS). The session thoroughly reviewed and analysed the terms of reference and work plan of the IPET so as to ensure that the team understood the expectations and requirements of WMO Members for international development and coordination of weather radar systems. This was also aided by presentations that were made by participants on national, regional and data user priorities and requirements and the analysis of results of a brief survey that was conducted by WMO prior to the session. The IPET acknowledged and agreed on the need to ensure continuity and support for previous and ongoing WMO activities relating to weather radar, including in particular the development of international weather radar data exchange, the development and maintenance of regulatory and guidance materials, the operation of the WMO Radar Database and also collaboration with relevant international organizations, including ISO. The meeting also discussed and decided upon requirements for new and additional activities to be addressed by the team, including support for WIGOS and the development of OSCAR/Surface and the WIGOS Information Resource, particularly focusing on metadata requirements, support for training, capacity development and new guidance that was likely to be centred around the development of a consolidated guide on weather radar operational best practice in areas such as calibration, data processing, quality control and monitoring. The team also recognised the need for the IPET to develop and provide guidance and expertise in relation to various policy issues, such as radio frequency protection and interference, wind turbine interference and data sharing. The team dedicated a significant amount of the session to further developing and refining the work plan of the IPET, with a view to completing and delivering several significant items over the coming year in the period before the next CIMO session.