Service Assessment

Spencer, South Dakota, Tornado

May 30, 1998

Photos: The Spencer tornado viewed from about 4 miles east of town on Highway 38 (courtesy of Keith Brown), and the Spencer water tower, an example of the catastrophic damage inflicted on the town (courtesy of Dr. Josh Wurman).

U.S. DEPARTMENT OF COMMERCE, William M. Daley, Secretary

National Oceanic and Atmospheric Administration, D. James Baker, Administrator,

National Weather Service, John J. Kelly, Jr., Assistant Administrator



Service Assessment Team
Event Summary
Facts, Findings and Recommendations
Appendix A: Fujita Tornado Intensity Scale
Appendix B: Spencer, South Dakota, Tornado, May 30, 1998, Chronological Log



The violent tornado which struck Spencer, South Dakota, on the evening of May 30, 1998, killed six residents and destroyed almost the entire town. The National Weather Service (NWS) conducted a Service Assessment to examine the effectiveness of the warning process that evening, focusing on the performance of the Next Generation Weather Radar (NEXRAD) Weather Service Forecast Office (NWSFO) at Sioux Falls, the usefulness of NWS warnings and forecasts from the perspective of our partners in the media and emergency agencies, and the public response.

Service Assessments are critical to the ongoing efforts of the NWS to improve the quality and timeliness of our warning and forecast services, especially as offices like NWSFO Sioux Falls complete the transition to a fully modernized Weather Forecast Office (WFO). By reviewing the performance of one operational team at one forecast office during one such devastating event, we look for ways to ensure that the application of new technology and new concepts will yield the most timely and accurate warnings and forecasts.

John J. Kelly, Jr., Assistant Administrator for Weather Services, August 1998

Service Assessment Team

The NWS assembled a Service Assessment Team to review the effectiveness of the warning process during the evening of May 30, 1998, when a violent tornado struck the town of Spencer, South Dakota. The team met in Sioux Falls on June 2 and spent the following 3 days in South Dakota collecting information and conducting interviews with the NWS staff at the Sioux Falls NWSFO, emergency managers, law enforcement officials, media representatives, and a number of residents of Spencer. Additional information was obtained from the NWS Storm Prediction Center (SPC) in Norman, Oklahoma, from other NWS meteorologists who participated in post-storm damage surveys, and from engineers at the National Institute of Science and Technology.

The team was comprised of the following individuals:

Dennis H. McCarthyTeam Leader, Meteorologist in Charge (MIC), NWSFO Norman, Oklahoma
Ricky L. ShanklinWarning Coordination Meteorologist (WCM), NEXRAD Weather Service Office (NWSO) Paducah, Kentucky
Patrick J. SlatteryPublic Affairs Specialist, NWS Central Region Headquarters, Kansas City, Missouri
James G. LaDueMeteorologist (Instructor), WSR-88D Operational Support Facility, Operations Training Branch, Norman, Oklahoma
Randall C. DuncanEmergency Management Coordinator, Cowley County, Kansas, President, International Association of Emergency Managers
Other valuable contributors include:
D. Gregory HarmonMIC, NWSFO Sioux Falls, South Dakota
Todd A. HeitkampWCM, NWSFO Sioux Falls, South Dakota
David L. AndraScience and Operations Officer (SOO), NWSFO Norman, Oklahoma
Brian E. SmithWCM, NWSFO Omaha, Nebraska
William F. BuntingWCM, NWSO Pleasant Hill (Kansas City), Missouri
Michael FosterSOO, NWSFO Fort Worth, Texas
David A. ImyChief, Operations Branch, NWS SPC, Norman, Oklahoma
David DowellGraduate Research Assistant, University of Oklahoma
Long PhanNational Institute of Science and Technology
Dat Duthinh
William H. LernerWeather Service Headquarters (WSH), Office of Meteorology, Silver Spring, Maryland
Linda S. KremkauTechnical Editor, WSH, Office of Meteorology, Silver Spring, Maryland
Argus LeaderDaily Sioux Falls Newspaper


AFOS: Automation of Field Operations and Services
AWIPS:Advanced Weather Interactive Processing System
CAPE: Convective Available Potential Energy
CDT:Central Daylight Time
CRS:Console Replacement System
CWA:County Warning Area
DOW:Doppler on Wheels
EAS:Emergency Alert System
EMWIN:Emergency Management Weather Information Network
GOES:Geostationary Operational Environmental Satellite
HMT:Hydrometeorological Technician
MCD:Mesoscale Convective Discussion
MIC:Meteorologist in Charge
m/s: meters per second
NAWAS:National Warning System
NEXRAD: Next Generation Weather Radar
NOAA:National Oceanic and Atmospheric Administration
NOW:Short Term Forecast (product identifier)
NWR:NOAA Weather Radio
NWS:National Weather Service
NWSO:NEXRAD Weather Service Office
NWSFO:NEXRAD Weather Service Forecast Office
NWWS: NOAA Weather Wire Service
PC:Personal Computer
PDS:Particularly Dangerous Situation
PSD:Peripheral Sharing Device
PUP:Principal User Processor
RFD:Rear Flank Downdraft
ROTATE:Radar Observation of Tornadoes and Thunderstorms Experiment
SEL:Severe Thunderstorm or Tornado Watch (product identifier)
SFP:State Forecast Product (product identifier)
SOO: Science and Operations Officer
SPC:Storm Prediction Center
SPS:Special Weather Statement (product identifier)
SVR:Severe Thunderstorm Warning (product identifier)
SVS:Severe Weather Statement (product identifier)
SWO:Severe Weather Outlook (product identifier)
TOR:Tornado Warning (product identifier)
TVS:Tornado Vortex Signature
VCP:Volume Coverage Pattern
WCM:Warning Coordination Meteorologist
WFO:Weather Forecast Office
WISE:Warning and Interactive Statement Editor
WSH: Weather Service Headquarters
WSR-88D:Weather Surveillance Radar-1988 Doppler
ZFP:Zone Forecast Product (product identifier)
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