A variety of non-meteorological returns seem to trigger the NTDA. In the attached image there are 3 NTDA icons within ~25 miles from the RDA. All have “Prob” values less than 30%. There were other examples from earlier in the day where bad radials and elevated roadways caused detections. All of these were also less than 30% prob. So I can see why the default threshold for the NTDA is >= 30%. I was assuming that the probability from the NTDA represents the actual probability of a tornado occurring based on the training cases. To me I would want the NTDA to pick up on anything that would be even a slight potential for a tornado. That way I could use it as SA or a first alert. I would be concerned if the NTDA was predicting a 22.7% probability of a tornado, like in the screen capture below. That to me means similar detections from the training cases produced a tornado about 1 out of 5 times. To see a non-meteorological return produce that high of values would lower my confidence in real returns. Rather than setting the threshold at >=30% I think that filtering out the bad detections  would make me trust the NTDA more.

– Gerry Bertier