Using the isentropic analysis for the operational short-range weather forecast

The software is described, developed within the meteorological geographical information system (GIS Meteo) technology, intended for the operational plotting of isentropic analysis charts. The study of atmospheric processes is carried out by the example of a concrete event, an unexpectedly heavy snowstorm in Moscow region on December 7, 2009. It is revealed that the potential vorticity anomaly formed over Moscow region favored the generation of cyclonic circulation in the lower troposphere and the ascent of the air being close to the saturation. According to the observation data, the precipitation was of convective type, although no convective instability was revealed. The study of the equivalentpotential vorticity evolution in the lower troposphere demonstrated the presence of conditional symmetric instability causing the development of the moist slantwise convection.