Slow moving storms might provide the most hail data points because cross-sections may be more tightly spaced if we are making verification calls immediately following passage of the storm. Supercell storms exhibiting the three body scatter signature, or "hail spike", as seen above should be investigated since they will contain some of the largest hail. The current multi-radar hail algorithm database has a small number of large hail reports, making it difficult to verify when the algorithm is doing a good job of diagnosing large hail.
The Maximum Expected Size of Hail (MESH) swath, or the "hail swath", as pictured above, shows a temporal maximum of MESH. In the picture above, the hail swath for the southeast-moving supercell above is shown. The gray lines indicate where the cross-sections should be taken.
While it would be ideal to cover the entire cross section, this may not be possible due to lack of locations available to call or time constraints. However, note that the cross sections go outside of the hail swath; this is an important part of the experiment because it will provide about the correct forecast of non-events as well as misses of the algorithm. Also note that the cross-sections are taken around the area where the algorithm produced a maximum in MESH. It is important to take cross-sections around this area and downstream, as illustrated above. Note that the largest hail reports in this case are downstream and to the right of the MESH maximum.
Go back to data collection strategies.