Exceptional sea level oscillations and strong current reversals, observed in the east Adriatic on 27 June 2003, are analyzed using available meteorological and tide-gauge measurements and numerical model results. It is shown that the variability in the atmosphere-sea system was characterized by high frequencies (0.01--0.1 min-1) and sea level and current amplitudes surpassing 1 m and 1 m s-1, respectively. The event was related to the occurrence of a gravity disturbance in the atmosphere above the Adriatic. The disturbance traveled toward the east-southeast at a speed of 22 m s-1 and was resonantly coupled with a wave in the sea 50 m deep. The resulting forced wave was further amplified when entering funnel-shaped bays opened to it. There are indications that the forcing disturbance and its counterpart in the sea excited normal modes of the bays and harbors in the area. Moreover, nonlinear steepening of the forced wave seemingly occurred, resulting in the formation of high-frequency wave trains. This process, along with the generation of coastal seiches, could explain the observed and modeled differences between the spectra of coastal variability and the spectrum of forcing wave.