An embedded supercell produced a significant tornado just west of the KLSX radar near St. Louis around 6pm CDT. The tornado produced a tornado debris signature and impressive debris ball (>65 dBZ) at its peak intensity.

The tornado debris signature reached a height of ~10kft at the 10 degree elevation scan, characteristic of an EF-2 tornado.

This case provides a great opportunity to investigate the performance of CPTI. The algorithm identified a maximum probability of strong tornadoes of 22% and a maximum low-level AzShear value of 0.030 /s. Based on the AzShear value, it seems the CPTI for strong tornadoes should have been stronger.

A little digging showed that the MRMS STP value was 0 near St. Louis, while the SPC Mesoanalysis page showed an STP of 4. This discrepancy explains the suppressed strong tornado CPTI and should be investigated. Perhaps there is a latency issue with the MRMS STP data.

I really like the CPTI product for clear-cut tornadoes and see it being very helpful for IBW updates for an ongoing tornado.

-Atlanta Braves