SINFONY - the combination of Nowcasting and Numerical Weather Prediction at the convective scale at DWD

There are different "optimal" forecast methods for different forecast lead times and different weather phenomena. Focusing on precipitation and convective events up to some hours ahead, radar extrapolation techniques (Nowcasting) show good skill up to about 2 h ahead (depending on the situation), while numerical weather prediction (NWP) outperforms Nowcasting only at later hours. Ensembles of both Nowcasting and NWP help to assess forecast uncertainties.

DWD's new Seamless INtegrated FOrecastiNg sYstem (SINFONY) combines forecast information from Nowcasting and NWP in an optimized way and as a function of lead time to generate seamless probabilistic precipitation forecasts from minutes to 12 hours. After four years of research and development, SINFONY is about to come to life in the upcoming two years, with an initial focus on the prediction of severe convective events.

For the development of SINFONY, different interdisciplinary teams work closely together in developing

• Radar Nowcasting ensembles for precipitation, reflectivity and convective cell objects
• Hourly SINFONY-RUC-EPS NWP on the km-scale with extensive data assimilation of high-resolution remote sensing (radial wind, reflectivity and cell objects from volume radar scans; Meteosat VIS channels; lightning)
• Optimal combination of Nowcasting and NWP ensemble forecasts in observation space (precipitation, radar reflectivity and cell objects)
• Systems for common Nowcasting and NWP verification of precipitation, reflectivity and objects.

For the SINFONY-RUC-EPS, new innovative and efficient forward operators for volume radar scans and visible satellite data enable direct operational assimilation of these data in an LETKF framework. Advanced model physics (stochastic PBL scheme, 2-moment bulk cloud mircophysics) contribute to an improved forecast of convective clouds.

As input for the combination of NWP and Nowcasting information, SINFONY-RUC-EPS generates simulated reflectivity volume scan ensembles of the entire German radar network every 5 min online during its forecast runs. Ensembles of composites and cell object tracks are generated by the same compositing and cell detection- and tracking methods/software packages, which are applied to generate the Nowcasting information.

To help evolve DWD's warning process for convective events towards a flexible "warn-on-objects", our Nowcasting- and NWP cell object ensemble forecasts are then blended into a seamless forecast ("probability objects") in a pragmatic way. Gridded combined precipitation and reflectivity ensembles are also under development, targeted towards hydrological warnings.

In addition to the development of SINFONY itself, focus is also put on the interaction with users (e.g. from flood forecasting centres) along the weather information value chain for co-designing the development of new forecast products and approaches to improve the prediction and warning process.

This presentation will introduce the goal and the concept of SINFONY and provide an overview on the ongoing developments as well as on the incipient interaction with users.