NowCastMIX: Automatic Integrated Warnings for Severe Convection on Nowcasting Time Scales at the German Weather Service

Abstract

NowCastMIX is the core nowcasting guidance system at the German Weather Service. It automatically monitors several systems to capture rapidly developing high-impact mesoscale convective events, including 3D radar volume scanning, radar-based cell tracking and extrapolation, lightning detection, calibrated precipitation extrapolations, NWP, and live surface station reports. Within the context of the larger warning decision support process AutoWARN, NowCastMIX integrates the input data into a high-resolution analysis, based on a fuzzy logic approach for thunderstorm categorization and extrapolation, to provide an optimized warning solution with a 5-min update cycle for lead times of up to 1 h. Feature tracking is undertaken to optimize the direction of warning polygons, allowing individual, tangentially moving cells or cell clusters to be tracked explicitly. An adaptive ensemble clustering is deployed to reduce the spatial complexity of the resulting warning fields and smooth noisy temporal variations to a manageable level for duty forecasters. Further specialized outputs for civil aviation and for a public mobile phone warning app are generated. Now in its eighth year of operation, a comprehensive and complete set of thunderstorm analyses and nowcasts over Germany has been created, which is of unique value for ongoing research and development efforts for improving the system, as well as for addressing climatological aspects of severe convection. Verification has shown that NowCastMIX has helped to significantly improve the quality of the official warnings for severe convective weather events when used within the AutoWARN process.

Impact Forecasting to Support Emergency Management of Natural Hazards

“…In this case, it is very likely that there will be a risk to life, substantial disruption of mobility and energy supplies, and widespread damage to property and infrastructure. Similar systems exist from several NWS, such as Meteo France or the German Weather Service (James et al, 2018). The warnings issued by the U.K. Met Office are depicted using the same 4 × 4 matrix used for windstorms ( Figure 4) based on the combination of expected impact severity and the likelihood of those impacts (Neal et al, 2014).…”

Ambient conditions prevailing during hail events in central Europe

“…Above all, the results can (and should) be considered in the forecasting of SCSs for lead times between 1 and 12 h. This time range is of considerable importance for many users as well as for issuing warnings of SCSs associated with high-impact weather phenomena such as hail, heavy rainfall, or severe wind gusts. In the hierarchy of prediction models, this time range is covered by nowcasting tools and very short-range forecasts (Nisi et al, 2014;James et al, 2018). Hence, convective indices, particularly SRH or DLS, might be employed in both systems.…”

Ambient conditions prevailing during hail events in central Europe

“…This time range is of considerable importance for many users as well as for issuing warnings of SCS/HS associated with high impact weather phenomena such as hail, heavy rainfall, or severe wind gusts. In the hierarchy of prediction models, this time range is covered by nowcasting tools and very short-range forecasts (Nisi et al, 2014;James et al, 2018). Hence, convective indices, particularly SRH or DLS, might be employed in both systems.…”