Hydrological forecasts are subdivided to:
flow forecasts with different lead time;
short-term - for 24 hours, 10 days;
- ling-term – for 1 month, three months and for vegetation and non-vegetation periods;
forecasts of floods;
forecast of development of ice phenomena on Amudarya river;
warnings on dangerous hydrological phenomena (mudflow danger, ice jams and ice dams on Amudarya, sudden changes of water content);
Long-term flow forecasts are based on the use of data of meteorological stations (precipitation and temperature), on surface and airborne snow surveys in the zone of flow formation. For producing of forecasts the statistical methods and mathematical models based on the use of meteorological and snow measuring information. However, because of the sharp reduction of the information volume in the zone of the river flow formation many forecasting methods are not used in practice. The Automated Information System for Hydrological Forecasting (AISHF) based on mathematical models enabling the calculations of the flow forecasts 1-6 months in advance for 16 water objects is currently used only for the rivers of Chirchik-Akhangaran basin and for the rivers of the northern part of Fergana valley.
Methods of the short-term flow forecasting are based on the data of radio sounding of atmosphere, they are not in use because of absence of data. Currently the graphical-and-analytical method is used.
Methods of development of the ice phenomena.
Since 1997 at Uzhydromet in the framework of the Swiss Aral Sea Mission the method for calculation of the snowmelt runoff is integrated step-by-step for different mountain basins.
The method is base on the data of the ground observations (daily data on the air temperature and precipitation registered at meteorological stations and discharge in the outlet) and snow cover area of the mountain territory by satellite data. This method is currently used for the short-term flow forecasting (1-3 days in advance) for the rivers of Chirchik, Akhangaran. Karadarya, Naryn and Vakhsh basins.
At present the work station of NRMP with the operation system for the flow forecasting (OSFF) is installed which will be used in the real time regime for the forecasts with different lead-time (1 day – 6 months) for the inflow to Charvak water storage. At present, for the certain reasons the forecasts are not calculated by the American model.
Standard criteria envisaged by the acting instructions are used as the criteria of quality of hydrological forecasting.
Reliability of hydrological forecasts of Uzhydromet is at present: 80-85% for the long-term, 90-95% - for the short-term, 100% - for the extent of awareness about the natural hydrological hazard.
Synoptician receives synoptic and upper-air data via local communication with Centre of communication. Data decoding and making-up of synoptic maps is made with the software in Synoptician AWP. The maximum lead-time of the Long-term forecasts, produced at Uzhydromet is 1 month. The method of forecasting is synoptic and based on the selection of the year-analogue. Besides the forecast for Republic of Uzbekistan at Uzhydromet the forecasts for the neighboring states: Turkmenistan, Republic of Tajikistan and Kyrgyz Republic are made. Seasonal weather forecasts at Uzhydromet are not made.
In the field of synoptic meteorology the main production of Uzhydromet is presented by: the short-term (for the current and subsequent 24 hours), medium-range (for 2-5 days) and the long-term (for 1 month) weather forecasts, as well as storm warnings about severe weather phenomena, snow and ice phenomena and sudden weather changes.
Reliability of the short-term and medium-range forecasts currently is: in winter and spring periods - 90-92%, in summer and autumn periods - 94-96%. The average efficiency of the storm warnings is 96%.