Improved thunderstorm detection, tracking and assessment products for Environment Canada radars

The primary analysis and display tool for the Canadian Meteorological Service's C-band radar data is the Unified Radar Processing (URP) software. URP produces basic conventional and velocity-based products. A more sophisticated suite of products is also produced that are designed detect and track thunderstorm cells, and to help assess their severity.

To improve these algorithms and products, forecast model data and lightning data have now been integrated with the radar data. A model data sounding can be interpolated in time and space to the storm cell site to assist in diagnosis. Total reflectivity volume and reflectivity volume colder than a threshold temperature are now used to identify a cell. Lightning data characteristics are then associated with each cell. The cell-tracking algorithm has been supplemented with knowledge of the change in cell volume, model winds aloft, and a mean observed motion of neighbouring cells. The hail algorithm has been adjusted to use a freezing level interpolated to the cell. Model wet bulb temperatures can be overlaid on radar data to attempt to help detect the bright band melting zone. Using model data, the radar data can now be displayed on constant temperature (CoTPPI) surfaces as opposed to constant altitude (CAPPI) surfaces. Model temperatures can now be overlaid on vertical cross-sections of radar data.

Doppler-based improvements have been made to the product suite. Vertical cross-sections of radial velocity can now be generated. Observed storm-relative radial velocities are shown with each cell. The Velocity Azimuth Display (VAD) has been augmented to allow winds to be displayed on a hodograph, as well as on a graph of wind barbs versus height. Wind shear and storm-relative helicity parameters are also calculated.

Finally, a number of further enhancements have been achieved. The Bounded Weak Echo Region (BWER) algorithm has been redesigned to improve detection and to reduce false alarms. The Rank Weight score for each cell has been modified to add the BWER volume, and to adjust the relative weighting of the algorithm's seven other parameters. The Storm Cell Identification Table (SCIT) has been improved to show detailed location and motion of the cell, BWER volume, BWER height, cell core volume, cell core volume less than -10C, as well as a number of lightning statistics. Loops of 5-minute base reflectivity are produced using the long range Doppler scan and the lowest elevation conventional scan with ground clutter filtering. Storm tracks are produced using a time integration of MaxR reflectivity above a certain threshold. The performance of the some of these new products will be presented.