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.
|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.