Warnings for tornadoes, severe thunderstorms and flash floods are some of the most important products issued by the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS). These warnings have historically included entire counties or parishes (mainly due to dissemination issues). Often, the risk of severe weather was only high for a small portion of the area actually warned. Large segments of the population were therefore needlessly warned to take shelter from the storm. A proposal to change to smaller, “storm-based” warnings is under consideration. In this paradigm, the area under warning is defined by a set of latitude and longitude points, and is easily ingested by graphical applications used on television, the Internet, and even cell phones.

Demonstration tests on the use of these smaller-than-county areas for convective warnings have shown several positive outcomes. An average reduction of 70 percent in the area covered by warnings during this test would equate to over 100 million dollars in savings to the public for reduced cost of sheltering (Sutter and Erickson, 2006). Emergency management and other disaster response agencies served by these warnings were able to focus their limited resources on smaller areas. Forecasters reported the ability to communicate tornado threats to the public with increased clarity and detail. Previous studies have shown that increased clarity and detail in warnings instills higher public confidence.

In this paper we identify several policy and socio-economic challenges to the implementation of storm-based warnings. Policy makers require both statistically sound and understandable performance metrics. Storm-based warnings require a change in verification methodology to match the change in warning methodology. Another challenge is to provide service for the portion of the public that receive warnings over the radio. This service is limited by the ability to describe the storm location and movement in a text format. The importance of location accuracy must be balanced by the ability of the user of the information to understand the location.

A critical element of this proposal is a strong commitment to collaboration between NOAA's NWS, academia (both in weather and social sciences), broadcast meteorologist, and private sector companies involved in the dissemination of warnings. This collaboration will help ensure that storm-based warnings are both effective and properly utilized, resulting in successful protection of life and property.