Rapid Update Cycle in DWD's Seamless INtegrated FOrecastiNg sYstem (SINFONY)

The SINFONY project at Deutscher Wetterdienst (DWD) aims to produce seamless precipitation and radar reflectivity ensemble forecast products for a time-range from minutes up to 12 hours. It combines numerical weather predictions (NWP) and forecasts from Nowcasting (NWC) with an initial focus on severe summertime convective events with associated hazards such as heavy precipitation, hail and wind gusts. Nowcasts at DWD are currently initialized with an update frequency of 5 minutes, while standard short-range numerical weather prediction (SRNWP) systems are initialized every three hours. Hence, in the worst case a three-hour old SRNWP-forecast had to be combined with an up-to-date Nowcast.

To overcome this issue, a rapid update cycle (RUC) is implemented, which initializes forecasts every hour with a potentially much shorter observation cutoff for the subsequent data assimilation step due to time criticality. To avoid growing differences between the atmospheric states in RUC and SRNWP, the RUC data assimilation cycle has a limited lifetime and branches off the SRNWP-cycle every 24 hours.

Besides the initialization frequency of the forecasts, the RUC also differs from the standard SRNWP in the data assimilation and the atmospheric model . The prediction of extreme convective events benefits for example from additionally available observation systems with huge data amount (e.g. satellites). Also, a more sophisticated microphysics scheme is applied differing from the SRNWP leading to a spin-up phase after branching off. However, this microphysics scheme helps to improve the results in reflectivity space compared to the SRNWP making a combination with NWC more feasible.

The large amount of involved additional observational data and more frequent forecasts is a challenge regarding stable data production, timeliness and handling at DWD.

We present ideas in terms of atmospheric parameters, related data flow, involved infrastructure, and results for the convective season of 2022. The latter topic will also touch upon outcomes of a first evaluation of the SINFONY-RUC with the DWD forecasters.