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Types of Precipitation - interpretation and effects

The method of assessment of the type of surface precipitation by the atmospheric model depends primarily upon the temperature structure of the model atmosphere although humidity is relevant too.  Small differences in structure in the region where the precipitation is being generated and in the layers through which the droplets fall can both have a major impact.  A change from rain at the surface to snow can be brought about by cooling of the airmass by evaporation or melting as the precipitation falls.  A major weather hazard is freezing rain which requires a very specific and rare lower tropospheric temperature and humidity structure.  Modelling of all these processes can be difficult, especially if the structure of the model atmosphere is initially imprecisely defined.  Forecasters need to assess the structure of the lower layers of the atmosphere, particularly when warm air is advancing over a very much colder airmass.

A range of charts and diagrams of precipitation types are available on ecCharts. 

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• See the section regarding types of precipitation output for a description of available charts.
• Read more on the probability of precipitation type products.