The Nordic tradition of weather radar networking is transnational by its very nature. The main stage project developed this further by creating the world's most advanced international weather radar network. The BALTRAD network is decentralized, preserving the partnership's transnational integrity. In practice this means that each partner exchanges data from its weather radars with other partners on equal terms. Our network is the most advanced in the world in the sense that it is the first time data from the latest generation of polarimetric radars are being exchanged internationally in real time. The common so-called BALTRAD "toolbox" is then used by each partner to process all data according to the needs of that individual partner. Using the common toolbox ensures that data processing methods are open, transparent, and therefore predictable, and the decentralized nature of the network also ensures that the way the toolbox is used is not dictated. This concept is optimal for technology and knowledge transfer, serving to mitigate regional imbalances, thus strengthening the BSR. Based on the successes of the main stage project, the aim of the extension is to transform the development investment into a permanent operational investment, replacing legacy systems where relevant. The cooperation agreement signed by the partners towards the end of the main stage project will be the starting point, proving that the concept is convincing and that it leads to sustainable BSR infrastructure. Germany, Lithuania and Norway were missing in the main stage project but are now on board as envisaged, thus achieving complete BSR participation. The partnership is further complemented by two Danish partners that address an important user group: municipal water authorities that need accurate rainfall estimates to optimize their water management practices. Several associated organizations give their support as well.The extension stage is centred around clear transnational investments, mostly for computer hardware. Although IT hardware is relatively cheap, it is worthless without intelligent software. Effort must be devoted to installing, maintaining, and training staff using the complete solution. Consequently, the total transnational investment in BALTRAD+ comprises the hardware and labour costs associated with our common software. We therefore see the total cost as transnational investments. The real added value of BALTRAD+ is the establishment of a durable system with quality-driven services that become an integral part of regional infrastructure. In addition, the continued work with end users will lead to more and better products customized for the needs of local, national, and regional applications to improve services for road and railway control and protection, aviation, radiation safety, civil protection, urban water management, and agriculture. Achievements: Building on the achievements of the main-stage project BALTRAD the work on the tasks to further develop the BALTRAD network in its functionality and completeness continued seamlessly. The main achievements are: - Several tools that are needed to jointly develop the BALTRAD system in an efficient manner and to foster the cooperation of the system developers have been implemented. Preference has been given to open source solutions, a prerequisite to guarantee that the final results of the project will be available for the public. - Towards the end of the project Version 2.0 of the BALTRAD system has been rolled out. The software package is freely available at http://git.baltrad.eu/ - One of the cornerstones in managing weather radar data is quality assurance. It is not trivial to specify and to deploy methods, procedures and algorithms for a harmonized processing of data according to agreed principles. Meanwhile several algorithms to improve the quality of weather radar data have been implemented and validated. The documentation on how quality assurance will be achieved is documented and publicly available (http://git.baltrad.eu/trac/wiki/cookbook/ Well- defined and thoroughly- implemented quality assurance guarantees that differences in the quality of the final products (e.g. rain and snowfall estimates short term weather forecasts) are minimized of the same quality irrespectively from which operator of weather radar systems the raw data are delivered. The end-users throughout the Baltic Sea Region will benefit from this. - Addressing the needs of end-users and receiving feedback from practitioners is a focus of the project. Taking account of the experiences from the main-stage project we are organising in each reporting period a so-called “BALTRAD User Forum). The first event of this type has been held on 15/16th May 2012 in Krakow, Poland. The second BALTRAD user forum was held on 4/5th December in Norrköping, Sweden. The third user forum took place on 16th May 2013 in Vilnius. The fourth user forum took place on 21/22nd November 2013 in Berlin. - BALTRAD reached interests beyond the BSR region. The Ukrainian Hydrometeorological Center (UHMC), the national meteorological institute in Ukraine and the Russian Federal Service for Hydrometeorology and Environmental Monitoring (ROSHYDROMET) joined the partnership by signing the BALTRAD Cooperation Agreement. This agreement governs the mutual exchange of weather radar data for official use of the partners beyond the project lifetime and includes provisions for new members to join. Furthermore, a co-operation with the Australian Bureau of Meteorology has been achieved.