U.S. Department of Commerce


Date of this Version



Presented at American Meteorological Society, The 21st Conf. on Severe Local Storms and 19th Conf. on Weather Analysis and Forecasting/15th Conf. on Numerical Weather Prediction, August 16, 2002.


Improving the amount of advanced warning time (lead time) for tornado warnings is one of the goals spelled out in the National Weather Service (NWS) Vision 2005 Strategic Plan (1999). Since the beginning of the NWS modernization effort, tornado warning lead times have increased from four to ten minutes, with the goal of 15 mi nutes set for 2005. In concert with increasing lead times, the NWS also has goals in place for increasing the probability of detection (POD) while decreasing the false alarm rate (FAR).
Accomplishing these goals will be no easy task. Rothfusz (2000) noted that forecasters may have reached a practical limit in tornado FARs until there ar e further advances in remote sensing technology and/or our understanding of tornadoes. The procurement of the weather event simulator (WES) should prove to be a very beneficial tool to aid in the understanding part of the equation. The WES simulates the AWIPS workstation used by the NWS. Forecasters are able to archive weather events as they occur and then review the case to gain a better understanding of the meteorological situation. In addition, training cases can be developed and administered to the operational staff at the beginning of the season (winter and convective events), to ensure operational proficiency.
When it comes to protecting the lives of citizens during hazardous weather situations such as tornadoes, another question that needs to be addressed is “How much lead time does the public want or need in order to take shelter?” This is a rather complex issue and won’t be resolved in the confines of this paper. However, as a first look, the authors sent questionnaires to two user groups in the Hastings Nebraska county warning area (GID CWA). One group included elementary and secondary schools, while the other consisted of hospitals and assisted living facilities (HAL). A cover letter was included with the questionnaire explaining our goals and also to define warning lead time. The number of responses returned was encouraging, confirming the importance of the subject.
The two groups sampled represent parts of the population where one, or maybe a couple of people, have to make decisions that affect many lives, namely when to take shelter. There are other organizations in a similar circumstance, but as a starting point schools and HALs were selected.