Using advanced numerical techniques and data assimilation (ROMS 4D-Var) at the same time with modern observations in a dynamically consistent way we aim to improve knowledge of the Adriatic Sea dynamics. During the project we will explore open questions in the field of physical oceanography of the Adriatic Sea: (I) dynamics of the dense water (DW), especially flow at the eastern side of the Adriatic Sea, (II) dynamics of the Po river outflow during stratified and vertically homogeneous conditions, as well as (III) generation and dynamics of the sharp Istrian temperature and salinity front. In order to capture those phenomena we plan to use advanced field observations (ADCPs, CTDs, towed CTD profiler, underway ship CTD), as well as high resolution nested numerical models. This type of measurements could arguably prove hypothesis on the importance of the East Adriatic DW contribution to the overall northern Adriatic DW budget. Measuring synchronously at all important entrances of the Kvarner Bay, we can determine time-evolving dynamics of this socio-economically important region. ROMS 4D-Var system is a powerful tool capable to provide insight into a optimal observation setup, predictability and limits of the linearized adjoint techniques for a shelf sea as the Adriatic. Results from the project could serve as basis for other research fields like ocean biology (DW bringing O2 at the bottom), chemistry or geology, or even applied like oil spills, integrated environmental planning where correct dynamics is of a crucial importance. The project team members come from the four institutions: Ruđer Bošković Institute, Faculty of Science, Croatian Meteorological and Hydrological Service, and Hydrographic Institute bringing unique competences for the proposed project to succeed. Last but not least, it is important to emphasize that after the project completion, all the insitu collected and model data will be made available to the scientific and applied research community.