The Role of Ground-Truth Reports in the Warning Decision-Making Process during the 3 May 1999 Oklahoma Tornado Outbreak

Abstract

During the devastating Oklahoma tornado outbreak that began just after 1600 central daylight time (CDT) on 3 May 1999, timely ground-truth reports of severe weather played a critical role in the warning decision-making process at the National Weather Service (NWS) Weather Forecast Office (WFO) in Norman, Oklahoma. Reports from storm spotters, emergency managers, media crews, and law enforcement officers went directly to the WFO staff via amateur (ham) radio, the National Warning System (NAWAS), and telephone. Warning forecasters also viewed live images of tornadoes as they were broadcast continuously by local television stations. These timely reports and the ability to communicate in real time with observers in the field provided NWS warning forecasters with valuable information to combine with Doppler radar data. Reports not only contributed to timely warnings but also enabled forecasters to add more detail and credibility to critical warning messages. The unprecedented warning service provided during this event demonstrated the effectiveness of a fully integrated warning decision and dissemination system and contributed to saving hundreds of lives.