About HHFS hydrological forecast
HHFS produces every morning 6-day lead time water level forecasts for Danube, Tisza, Drava rivers and their tributaries. Depending on the arrival time of observation and forecast data from Hungarian and other European hydrological services, hydrological forecast are issued between 9 and 11 a.m. In flood situations or in case of significant missing data, forecast issue time can shift to after 11 a.m.
During flood events forecasts are issued more times a day including the most up-to-date measurements and meteorological forecasts. Forecasts are produced for several stations on Hungarian reaches of Danube, Tisza and Drava rivers and their most important tributaries.
During forecasting procedure meteorolgical and hydrological conditions of the past period are considered, as well as the expected values of precipitation and temperature for the lead time interval.
After all meteorological and hydrological data are processed, forecast activity follows. HHFS has its own developed forecasting system which consists of several functional modules running one after another. In the first module snow ablation and melting processes are considered. The next module is the rainfall-runoff module. It is followed by the flow routing module calculating movement of water in the channel. The next module is the back water effect module which takes into account the effect of dams and also of other rivers. Finally, adaptivity of the forecasting model is assured by error correction modules.
Forecast accuracy is expressed by objective numbers determined with statistical analysis of previous years' forecast errors. The error interval is defined based on last years' root-mean-square error. Since forecast errors can be described by normal distribution function, it is expected that water levels remain within the error interval with the probability of 70%.
Observed and forecasted water level values might exceed alert levels or the HHW level, or they might decrease under the LLW level. In order to draw attention to these superventions these levels are marked with certain colours.
- Exceed 1st alert level: yellow
- Exceed 2nd alert level: orange
- Exceed 3rd alert level: red
- Exceed HHW level: purple
- Decrease under LLW level: blue