This paper is an experimental investigation of a supersonic rectangular nozzle with aft deck used for three-stream engines. Correlations between time-resolved schlieren and near-field pressure were conducted. The jet utilizes a single expansion ramp nozzle (SERN) configuration along with multiple streams, operating at an ideally expanded bulk flow of Mj;1 = 1:6 and bypass stream of Mj;3 = 1:0. Time series were extracted from the schlieren images and correlated to hydrodynamic deck pressure. Since schlieren photography is an integrated view of the entire three-dimensional flow field, pressure sensor placements attempt to better identify flow physics. Proper orthogonal decomposition (POD) is then performed on the schlieren images and the time-dependent coefficients are related to the near-field deck pressure. Dynamic Mode Decomposition (DMD) is also applied to the schlieren field and the spatial modes are correlated to POD modes.