Thunderstorms in the Alps
In a mountainous region even relatively small but intense thunderstorms can produce local flash floods with severe consequences and damages. Strong convective cells can produce hail and dangerous wind gusts. A reliable prediction of such events must therefore have a high time and space resolution. At present this is only possible using nowcasting tools which combine remote sensing techniques like e.g. radar and satellites. Nowcasting corresponds to very short-range forecast in the time range from 0 to a few hours ahead. For such short-range forecasts numerical models are not yet sufficiently reliable and not updated often enough.
TRT thunderstorms cells (white contours), trajectories (white lines) and extrapolated cells (+1h, yellow contours), superimposed on the precipitation radar image.
Cell tracking principle.
TRT
In this context MeteoSwiss has introduced an automated, radar based tool called TRT (Thunderstorms Radar Tracking), as a part of its thunderstorms nowcasting, warning and information system. TRT performs in real-time an automated detection, tracking and characterization of intense convective precipitation systems. It uses the data of the Swiss radar network (composite image of 3 volumetric C-band Doppler radars) with a time resolution of 5 minutes and a spatial resolution of 2 km.
The radar data have already passed sophisticated clutter and quality check algorithms before the ingestion into the TRT-tool.
The detection algorithm identifies convective cells in a precipitation system. A cell is defined as a connected zone of radar pixels whose reflectivity exceeds a detection threshold. The tracking of thunderstorms is based on the method of the geographical overlapping of cells (see figure). Trajectories are then created from a sequence of radar images, indicating the movement of the centres of the cells. TRT forecasts storm movement by extrapolating the motion of individual cells up to 1 h, and gives thus a tendency for the expected position.
TRT is developed by MeteoSwiss in collaboration with Météo-France. It is derived from the severe thunderstorms algorithms developed for the RDT product (Rapid Developing Thunderstorms), a tool for the detection of convection in the infrared satellite images.
In this context MeteoSwiss has introduced an automated, radar based tool called TRT (Thunderstorms Radar Tracking), as a part of its thunderstorms nowcasting, warning and information system. TRT performs in real-time an automated detection, tracking and characterization of intense convective precipitation systems. It uses the data of the Swiss radar network (composite image of 3 volumetric C-band Doppler radars) with a time resolution of 5 minutes and a spatial resolution of 2 km.
The radar data have already passed sophisticated clutter and quality check algorithms before the ingestion into the TRT-tool.
The detection algorithm identifies convective cells in a precipitation system. A cell is defined as a connected zone of radar pixels whose reflectivity exceeds a detection threshold. The tracking of thunderstorms is based on the method of the geographical overlapping of cells (see figure). Trajectories are then created from a sequence of radar images, indicating the movement of the centres of the cells. TRT forecasts storm movement by extrapolating the motion of individual cells up to 1 h, and gives thus a tendency for the expected position.
TRT is developed by MeteoSwiss in collaboration with Météo-France. It is derived from the severe thunderstorms algorithms developed for the RDT product (Rapid Developing Thunderstorms), a tool for the detection of convection in the infrared satellite images.
Online documentation of Swiss radar network.pdf, 914 KB
Operational applications
Nowcasting and monitoring of severe thunderstorms, pre-alert for intense convective systems, decision-making aid for convection warning to civil protection authorities and to the general public.
Contact
MeteoSwiss, Radar and Satellites, CH-6605 Locarno-Monti, Switzerland
Nowcasting and monitoring of severe thunderstorms, pre-alert for intense convective systems, decision-making aid for convection warning to civil protection authorities and to the general public.
Contact
MeteoSwiss, Radar and Satellites, CH-6605 Locarno-Monti, Switzerland
