The Spencer SD Tornado of 30 May 1998

Al Moller's storm intercept account


South Dakota Tornadoes 5/30/98

By Alan Moller , NWSFO FWD

Patricia Clay (my girlfriend) and I documented much of the 5/30/98 local tornado outbreak in the Spencer/Alexandria South Dakota area, through 35 mm slides and video. We began the morning in Alliance, Nebraska, by watching the Weather Channel. Noting that a huge mass of cirrus was moving towards the Iowa portion of the morning SPC risk area (bad for severe weather), we decided to target an area further northwest. Specifically, we were interested in the late afternoon intersection of the dry line and warm front in southeast South Dakota, as depicted by the Weather Channel's forecast map. (we later found out that the "warm front" actually was an outflow boundary).

After a long approach, we began chasing storms just east of the Missouri River on I-90. The early storms near and north of I-90 were up and down rather quickly; so we turned north on highway 45 towards fresh, very vigorous TCu to our north. Moving north and east, we intercepted storms near Huron, for which tornado warnings were issued. Based on visual contact with the southernmost of these cells (north of Alpena) we decided that it was outflow-dominant. Thus, we moved south and east, ultimately coming across the Spencer supercell.

SLIDE AND INTERCEPT DESCRIPTIONS (linked to photos):

  1. Looking east from 10 east of Valentine NE - sheared TCu along the SSW-NNE oriented dryline.
  2. Looking north from Highway 183 near the NE-SD border, we note scattered TCu on the dryline and an E-W line of isolated TCu intersecting the dryline in the distance. At the intersection (or close to it from out limited viewpoint) was the first multicell Cb, behind LHS of the large grove of trees. This was our first target storm. On the extreme LHS of the photo is anvil cirrus streaming east from the western SD storms.
  3. The first storm (previous slide) fell apart; so we committed to storms farther north. As soon as we did, we had this view in the rear-view mirror -- the first explosion of the Spencer storm! It is the background storm, behind the highly-sheared TCu. Note the small horizontal funnel out of the dark side of the TCu! We knew to disregard this shear funnel. Nevertheless, when I saw this early view of the Spencer storm, we backtracked and went east on Highway 34. We took Highway 34 so we could choose from east-moving storms north and south of us. We turned north to Alpena, saw that storms to our north were undercut by outflow, and hustled S and E along Highway 37. We observed two left moving storms split off of the Spencer storm, and deviated around them to get to the "right-moving action area".
  4. Moving south on Highway 37 toward Mitchell, about 18 mi north of town, we saw a rain-free base (RFB), with an apparent rain hook (RHS of road) wrapping around a rapidly rotating wall cloud.
  5. Wall cloud now on LHS of Highway 37, about 10 mi north of Mitchell. Note carved-out RFD (upper part of photo) on outflow side of mesocyclone. [Many clear slots have a carved-out appearance -- such as this -- rather than a literal clear slot.]
  6. 85 mm view of rapidly developing tornado NNE of Mitchell. Note the thin, ragged funnel and very thin dust column beneath funnel.
  7. Another 85 mm view of the same tornado. Opaque dust column is still visible under funnel.
  8. First tornado. I estimate the time of this and the next two slides at between 807 and 811 pm.
  9. Another view of the first tornado between 807 and 811 pm.
  10. Another view of the first tornado. A new lowering at extreme LHS is intensifying.
  11. The tornado weakened a bit, exhibiting a very weak debris cloud, the strengthened again later. Also note the ominous -- and strengthening -- lowering on the LHS of the tornado (also visible in the previous two slides). Imentioned to Patti that a second tornado appeared to be imminent. As Patti shot video and I took slides, I fiddled with my 2-meter ameteur radio, trying in vain to find an active frequency.
  12. Here and in the next two slides, the reinvigorated tornado appears to approach the RHS of the ever-increasing lowering to its east, as if the new circulation (?) was trying to pull tornado #1 around it.
  13. Tornado #1 apparently nearing eastern lowering.
  14. Tornado #1 apparently approaching eastern lowering (wide angle view).
  15. Tornado #1 still moving ESE, apparently toward eastern lowering.
  16. Things become more confusing as the first tornado appears to dissipate and the large tornado forms -- looking SE. About this time an amateur radio spotter puled up in the northbound lane. I drove down to ask him if he was reporting the tornadoes and he nodded affirmatively. Slide shot with a 35 mm lens.
  17. Large tornado forming. Slide shot with an 85 mm F1.8 lens.
  18. I drove a short distance up the road and picked Patti up, and shot this slide and the next two.
  19. Large tornado.
  20. After this photo of the large tornado, we moved south on Highway 37and east on a gravel road.
  21. Looking ESE from the gravel road, probably a few mi NW of Fulton, as the Spencer tornado approached Spencer. We turned south on another gravel road and encountered damage from the first tornado.
  22. A few minutes later, at the Highway 38/local 25 intersection, looking east. We can only see rain wrapping around the meso. Fearful that a tornado was hidden in the grunge (there was!), we turned south on the local-25 bridge over I-90...
  23. ...and saw people driving wildly on I-90! They had seen this new tornado, which formed from the trailing Alexandria supercell, which probably exploded on the vorticity-rich outflow boundaryof the Spencer storm. This is looking WSW from the Highway 25 bridge above the eastbound lanes of I-90 (85 mm lens).
  24. The first Alexandria tornado weakened, with very little ground debris. This slide is looking west from Highway 25, about 1/2 mile south of I-90. Note the apparent RFD left of the weakened tornado.
  25. The first Alexandria tornado re-strengthened, with a smaller rope tornado developing quickly to its WSW. Note the better-defined RFD, due south of the tornadoes. Drivng slowly south, we caught the two tornadoes a mile or two to our west. They were moving SE.
  26. The rope ended abruptly...and the longer lived first tornado also weakened. The first tornado then briefly became more vigorous; but about 30 seconds later dissipated completely.
Notes: I cannot reconcile the slight differences between the photos and damage tracks, except to say this: I may have missed tornado track #2 in the messy dust/debris of the time frame of photos 15-20 in the above list, or, it is possible that the weakening trend we saw with tornado #1 (Fulton tornado) corresponds to the space between the first two tornado tracks in the survey? Furthermore, the Alexandria tornadoes from our vantage point apeared to be on a SW-NE oriented line from each other (rather than the NW-SE line depicted in the survey). Our "view" may have been an optical illusion. It also shows how difficult it is to tell what is going on, based only on the apearance of tornadoes in photos!

We were saddened to learn of the Spencer fatalities later that evening. I tried to raise someone on the amateur radio without success, finally locating the amateur (from Mitchell?) shortly before 825 pm. Apparently, I made the mistake of thinking spotters were all over the event, after talking briefly to the Mitchell spotter.


EDITOR'S NOTE: Al's storm intercept photos from this day are also on display in chronology with others' photos in the Fulton, Spencer and Alexandria tornado photo pages.


Back to Spencer Tornado Page