Characteristics of synoptic disturbances of the level in the range from a few weeks to months are estimated on the basis of frequency-directional spectral analysis of the Baltic Sea level fields obtained from satellite altimetric measurements. It is shown that synoptic disturbances with periods from 30 to 92 days have space scales from about 250 to 1400 km and propagate in different directions at a velocity of 7-31 cm/s. Comparison of altimetry-derived characteristics of synoptic level disturbances with theoretical dispersion relations of low-frequency waves made it possible to identify them as barotropic and baroclinic Rossby waves and baroclinic topographic waves.