On 24 November, 2001, Alabama experienced one of the largest tornado outbreaks in its history. A total of 36 tornadoes racked the state during a 10-hour period, including 24 in the northern and central counties comprising the National Weather Service (NWS) Birmingham county warning area. This particular event severely taxed the capabilities of WFO Birmingham, and provided an excellent case study for examining severe weather operations and warning decision making practices at a typical NWS office in the southeast United States.

On the whole, WFO Birmingham performed quite well during this event. Warnings preceded the vast majority of the tornadoes, and lead times averaged over 18 minutes. However, several tornadoes occurred with no adequate warning, including three F2 events which produced a total of 30 injuries. It is instructive to examine these missed events from a meteorological, technological, and human factors standpoint, since each of these played a role in the warning failures.

A new initiative for conducting post event reviews is being promoted at WFO Birmingham, one that incorporates an assessment of human factors such as workload and intra-office communication, in addition to traditional analyses of radar signatures and other meteorological elements. For this particular event, a comparison of the reflectivity and velocity signatures for the unwarned tornado group versus those of the total population offers some clues as to why these events were missed. Several staff issues were also ongoing at WFO Birmingham during the periods when the missed events occurred. Each of these factors had ramifications for the warning decision making process during this major severe weather event.

Several factors which likely led to the missed tornado events will be discussed at the conference. In addition, a blueprint will be offered for comprehensively assessing all the parameters associated with tornado warning decision making at current NWS offices.