Spencer tornado WNW of town

Observations and Damage Analysis of

The Spencer SD Tornado of 30 May 1998

Compiled by Roger Edwards, Storm Prediction Center

Latest update: 21 Jun 7


Overview

On 30 May 1998, the most destructive and second deadliest tornado in South Dakota history -- and the most intensely observed and analyzed -- struck Spencer SD. It began as a large, dust-cloaked tornado NW of Farmer, SD in Hanson County, concurrent with the demise of the "Fulton" tornado. Continuing toward the ESE, it struck several farmsteads before crossing the Hanson/McCook County line a half mile WNW of Spencer. At this time, the tornado was being observed by the OU Doppler on Wheels crew, whose mobile Doppler radar data showed up to 246 mph winds in the tornado a few tens of meters above ground level.

The now-violent tornado carved a 3/8 mile wide path directly across Spencer (see map below) between 2038 and 2044 CDT (0138-0144Z), destroying or damaging all but a few houses on the NE side of town. Six people died in and adjacent to what was a two-story apartment complex housing many elderly people. Damage was rated up to F4 in a narrow swath of the business district, located just SW of the center of town, becoming less intense a few blocks the N and S. Analyses of tornado imagery and damage indicated that, as it was going through Spencer, it was a large, single-vortex tornado; perhaps containing brief sub-vortices.

As the tornado was ravaging Spencer, teams of storm observers were stationed to its WNW, WSW and E. The map below shows their locations. Click on the links below the map to see a representative tornado picture from each angle.

Spencer tornado path

A Edwards/Marks, looking ESE B DOW (Dowell), looking ENE C Chang/Reid, looking W D Brown/Lisius, looking W E SUNYA (Corbosiero), looking NNE

The path turned slightly more toward the SE in Spencer. Within a couple of miles after leaving town, the tornado enlarged further and assumed more consistent multiple-vortex structure, sometimes having no clearly defined condensation funnel. Aerial damage surveys showed cycloidal spirals in field stubble during this portion of the path, a well-known indicator of multiple vortices.

Within minutes of assuming multivortex structure, the tornado became cloaked by fading daylight and by rain wrapping around its parent mesocyclone. Though spotters could not see the tornado anymore, a narrow, serpentine path through crop stubble indicated that it roped out in its final moments, instead of becoming diffuse while still large as with some violent tornadoes. The Spencer tornado continued winding ESE to SE toward Interstate 90, where it finally dissipated as another rain-wrapped tornado developed nearby.

The Spencer tornado was the third of six spawned by the same supercell thunderstorm. Another supercell developed on the rear-flank gust front of the Spencer storm and produced two more tornadoes. All the tornadoes from both supercells, along with their F-scale damage ratings, were mapped by Brian Smith of NWS Valley NE.


Detailed Information

Meteorological Data & Analyses

    A source of weather data on the event, with some meteorological interpretation. Will include satellite, radar, surface, and upper air data. More information will be added from time to time.

Spencer Damage Surveys and Damage Photos

    This is a large collection of 35 mm photos of the damage from ground and aerial surveys with explanatory captions. The images are 16.7 million color JPGs and are linked from their descriptions.

Spencer Tornado Pictures

    This is a large set of 35 mm photographs of the tornado itself in roughly chronological order, scanned into 16.7 million color JPG format. NOTE: This page contains many embedded images and may be rather slow-loading.

Fulton Tornado Pictures

    A set of photos of the Fulton SD tornado in chronological order. NOTE: This page contains embedded images and may be rather slow-loading.

Alexandria Tornado Pictures

    A set of photos of the Alexandria SD tornadoes in chronological order. NOTE: This page contains embedded images and may be rather slow-loading.

Storm Observers' Accounts: Chuck Doswell, Roger Edwards, Martin Lisius, Al Moller, William Reid

    First-hand stories provided by eyewitnesses of the Spencer tornado

Image Credits

    Read for more information on the photos used here.

F-Scale Exercise on Spencer, SD Tornado Damage

    Results of damage rating exercises using selected scenes from the Spencer tornado damage path


    Related Links

    1. CIMSS Satellite Analysis of the Spencer Supercell
    2. Radar and Damage Imagery from NWS Sioux Falls
    3. University of Oklahoma ROTATE-98 and Doppler on Wheels Imagery
    4. The South Dakota Public Broadcasting documentary page
    5. Andy Schmidt's Spencer Damage Photos