What is already known:
What this study adds:
The National Weather Service’s (NWS) current warning system has been in place for several decades. Research has shown it has limitations with more precisely depicting the area of tornado threats, and the inability to update the warnings without reissuance, among others. This has motivated scientists to develop new ideas for warning systems, one of which is called the prototype Probabilistic Hazard Information project. Research done on this tool shows that it has limitations, but also the potential for adding to or replacing the current warning paradigm. Nine NWS forecasters were brought into the NOAA Hazardous Weather Testbed in 2017 to test the tool and warning strategy by working through several weather cases. For this study, three cases of talk-aloud data from the forecaster issuing tornado PHI objects were analyzed to determine how they made tornado warning and advisory decisions using the new tool. Findings show that forecasters were able to use the tool to accurately predict tornado formation. In contrast, tornado maintenance was not anticipated as accurately, with the tool showing their confidence decreasing over the duration of time that each PHI object would be in effect (usually 60 min). These findings indicate that PHI is useful for conveying the prediction of tornado formation and shows promise for future use in the NWS warning paradigm.