How will X-band attenuation affect tornado detection in the CASA IP1 radar network?

Attenuation of radar signals by heavy rain and hail presents a significant challenge to tornado detection with a single fixed-based X-band radar. By using a network of radars, the chance of finding a sufficiently clear path between one of the radars in the network and a tornado is increased over any single radar. The goal of this project is to quantify the extent of the attenuation problem in tornadic storms by examining some recent Midwest tornadic storms. Initial calculations of attenuation from the “worst-case” viewing angle have been done by hand to verify the extent of the problem for a single radar. We proceed by remapping the data from five recent storms from the polar radar grid onto a high resolution Cartesian grid. We then calculate the attenuation for the radars in CASA radar network by resampling the gridded data, given all possible positions of the tornadic storm within the CASA IP1-A network domain. The result is the probability of obtaining sufficient signal strength at the tornado location for one or more CASA radars should similar storms appear during IP1-A operations.

Preliminary results have been obtained for one snapshot of the May 8, 2003 tornado near Oklahoma City. The parent storm of this tornado had a broad area of reflectivity over 50 dBZ. It is found that any individual radar would miss this tornado due to attenuation for 20.4% of the possible locations, but the IP1-A network as a whole is blind to the tornado in just 12.6% of the positions, as indicated by the red 0's in the figure. Results from a variety of tornado cases will be presented at the conference.