The World Meteorological Organization (WMO) World Weather Research Programme’s (WWRP) Forecast and Research in the Olympic Sochi Testbed program (FROST-2014) was aimed at the advancement and demonstration of state-of-the-art nowcasting and short-range forecasting systems for winter conditions in mountainous terrain. The project field campaign was held during the 2014 XXII Olympic and XI Paralympic Winter Games and preceding test events in Sochi, Russia. An enhanced network of in situ and remote sensing observations supported weather predictions and their verification. Six nowcasting systems (model based, radar tracking, and combined nowcasting systems), nine deterministic mesoscale numerical weather prediction models (with grid spacings down to 250 m), and six ensemble prediction systems (including two with explicitly simulated deep convection) participated in FROST-2014. The project provided forecast input for the meteorological support of the Sochi Olympic Games. The FROST-2014 archive of winter weather observations and forecasts is a valuable information resource for mesoscale predictability studies as well as for the development and validation of nowcasting and forecasting systems in complex terrain. The resulting innovative technologies, exchange of experience, and professional developments contributed to the success of the Olympics and left a post-Olympic legacy.

Described is the second stage of the work (2011-2014) on the implementation and development of the COSMO-Ru system of nonhydrostatic short-range weather forecasting (the first stage of the implementation and development of the COSMO-Ru system is described in [7,8]). Demonstrated is how the research activities and ideas of G.I. Marchuk influenced modern methods for solving the systems of differential equations that describe atmospheric processes (in particular, the version of the Marchuk's splitting method is used to find the solution of the finite-difference analog of the system of differential equations in the COSMO-Ru model); it is shown how he contributed to the development of the methods of assimilation of meteorological information associated with the use of adjoint equations. Given is a brief description of the COSMO model of the atmosphere and soil active layer, the COSMO-Ru system, and research activities on this system development. words: COSMO-Ru sys tem of mesoscale nonhydrostatic short-range weather fore cast ing, Marchuk-Rober semi-implicit method

The probability multimodel forecast system based on the Asia-Pacific Economic Cooperation Climate Center (APCC) model data is verified. The winter and summer seasonal mean fields T 850 and precipitation seasonal totals are estimated. To combine the models into a multimodel ensemble, the probability forecast is calculated for each of single models first, and then these forecasts are combined using the total probability formula. It is shown that the multimodel forecast is considerably more skilful than the single-model forecasts. The forecast quality is higher in the tropics compared to the mid-and high latitudes. The multimodel ensemble temperature forecasts outperform the random and climate forecasts for Northern Eurasia in the above-and below-normal categories. Precipitation forecast is less successful. For winter, the combination of single-model ensembles provides the precipitation forecast skill exceeding that of the random forecast for both Northern Eurasia and European Russia.

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