Spencer SD Tornado Damage

Damage Survey Summaries

The first ground survey was conducted all day on May 31 by Greg Harmon (MIC, NWS Sioux Falls), Ron Holmes (SOO, NWS Sioux Falls), Roger Edwards (Storm Prediction Center) and Steve Marks (Greensboro/Guilford County NC Emergency Management). Path crossings and measurements were done from near Farmer ESE to I-90, along with detailed, close-up investigation and documentation of damage in and near Spencer. Most of the damage was still unaltered outside the necessary removal of debris from roadways. Photos are numbered in the order they were taken.

While the ground survey was underway, Mike Foster (NWS Ft. Worth), Todd Heitkamp (NWS Sioux Falls) and Bill Bunting (NWS Pleasant Hill, MO) were performing an aerial flyover along the damage path. Mike's photography is linked mostly in scenes 1-11, over the ground damage sites.

Corresponding aerial photos from the subsequent aerial survey by Brian Smith (NWS Valley, NE) are linked for some of the scenes in Spencer (12-28), to provide the perspective from overhead. Brian's detailed aerial survey of this and the other SD tornado paths was the basis for his map of all the tornadoes on the evening of May 30.

Damage Descriptions & Imagery

Spencer SD tornado track and damage photo locations. Inset is damage path across Spencer.

The letters on the map above match the location of each photo linked below. Photos are numbered in chronological order. Be sure to note the direction of view, in order to gain a better understanding of the character of damage with respect to its position in the tornado path.

1. Site A, looking ENE. South wall and roof cleanly removed from wood frame farm home on the S side of the damage path. Lack of substantive roof-wall and wall-wall attachments is evident here -- but even more so in the next photo.

2. Site A, looking NNW. Same home as in Picture 1 but through missing south wall. Lack of attachments between wall and frame -- and between frame and roof -- is apparent in smoothness of remaining edges. Note that utility pole behind house (to its N) is still standing and leaning slightly toward the SE.

3. Site A, looking NNE. This overturned vehicle had been attached to a livestock trailer, unseen to the right and behind. It was separated and moved N into this position. Lack of apparent major impact damage, except where it landed on its front and top, indicate it did not bounce or drag -- but instead flipped over through the air before coming down on its top. See Picture 4 for livestock trailer.

4. Site A, looking N. Debris strewn through trees and part of a lake along W side of SD 24, in the central and northern part of the damage path. Some of this debris was blown N and NW into the lake from the farmstead, which was on a peninsula (as seen from above, looking NNE). Sheet metal piece in the left-background tree trunk may have been blown onto the trunk from the SE by the tornado, then swivelled around 180 degrees, weather-vane style, in the intense NW winds of the rear-flank downdraft (RFD).

5. Site A, looking WSW. Livestock trailer which had been overturned and blown onto SD 24. Immediately after the tornado, it was resting in an ESE-WNW direction across the west lane of SD 24, detached from the unseen vehicle now shown in Picture 3. Someone had moved it to the W, off the road, by the time of this photo, in order to remove a traffic hazard. The entire farmstead site is shown from above looking SW; the tornado moved from left to right (WNW-ESE) across the middle and top of the picture.

6. Site B, looking SSE. Concrete block foundation with house debris in basement. No anchoring is evident; note the smoothness of the top of the concrete blocks. In fact, every house on this survey which was removed from its foundation was either not anchored down at all, or weakly connected at best. This site is located at left in this view from above, looking SSW; tornado moved from right center to left center.

7. Site B, looking NE. Car was lifted from the driveway of the house in Picture 6 blown ENE (apparently in the SE quadrant of the tornado vortex) and flipped onto its top. This was in the middle or south part of the damage path. Most trees are leaning or broken toward the SE -- possibly with aid from the severe northwesterlies of the post-tornadic RFD. Cars can become airborne at speeds less than that needed to break some trees.

8. Site C, looking NE. Mobile home with its front end stripped in the southern part of the tornado track. This mobile home was not removed from its foundation because it was strapped into concrete using steel cables and ties. Meanwhile, the house to the left was pushed almost completely off its foundation, as shown in picture 9. Notice the lack of damage to the rear of the mobile home; while the outer walls were peeled off the front room. The house to its W acted as a windbreak, sheltering all but the front of the mobile home from the westerlies along the south edge of the tornado. In effect, the house was sacrificed to save the mobile home. This view from above looks NE across the scene, with the house and mobile home at right. Tornado moved from left to right.

9. Site C, looking NE. Wood-frame house pushed bodily off its concrete block foundation, toward the ESE, in the southern portion of the damage path. This is the house in the left side of Picture 8 and in the right side of this aerial shot. Note a lack of evidence of any attachment of the house to its foundation. Since the house remained intact and moved closer to the well-anchored mobile home to its E, it acted as a wind shelter to prevent all but the front of the mobile home from significant damage (as shown in the previous photo).

10. Site C, looking SE. Another view of the mobile home and displaced house, this time looking at their N sides. Concrete stair steps at lower right once led into the back extension of the house (center).

11. Site C, looking W. Dented propane tank with a happy face under an unmoved utility pole, W of the house and mobile home in Pictures 11-13. Deeply planted and without significant debris impact divots, the pole remained standing; though there was enough flying debris circulating around the vortex from the rest of this site to cut down the wires and dent the tank.

12. Site D, looking WSW. Unanchored mobile home destroyed in NE Spencer. It was blown toward the SW, off the gravel bed in foreground. Its steel bed had been sitting on the gravel, and was bent around the tree at center with the ends pointing S and W. Rubble of the mobile home itself was scattered southwestward toward the house at left rear. The white strip extending S from between the gravel bed and the tree is the concrete driveway; see the next photo for a NW view from the S edge of the driveway. This is a textbook example of the inherent danger of mobile homes in a tornado. Note how little damage occurred to the frame home, which was deeper into the tornado vortex. The block containing this damage is the first whole block shown in the upper right (NE) portion of this aerial view.

13. Site D, looking NW . Tree damage in Spencer, north of the path center. Note trees in background center blown down toward the W and SW, as may be expected in the N part of an ESE-moving tornado. Many trees in Spencer -- even near the path edge -- were denuded, broken and de-barked more than those in the portion of the damage path WNW of town. Even if the tornado was more intense in Spencer than elsewhere, this effect was at least partly caused by the large volume of airborne debris (boards, sheet metal, vehicle parts, glass, household objects, etc.) circulating within the tornado vortex once it began churning through town. Most of the foreground debris came from the destroyed mobile home in Picture 12.

14. Site E, looking ESE. Trees blown down toward the ENE near the center of the damage path. The vehicle leaning against the tree in left background is shown close-up in Picture 16.

15. Site F, looking ENE. 3 relatively undamaged homes in E-central Spencer, in the northern half of the tornado path. No structural damage is evident -- just broken or removed pieces of exterior wood facade, shingles removed and windows broken. Much of that can be attributed to impact from pieces of flying debris; there was less damage (unseen) on the N sides of these houses. The weakest winds within the tornado -- which was still a single large vortex -- would be expected here. [The photo was taken from within a much more intense portion of the tornado path.]

16. Site F, looking SSE. Vehicle wedged against broken tree, close to the path center. The vehicle was blown ENE off a driveway to the right (unseen); and the tree was broken ENE. Given the tornado track, this final positioning of tree and vehicle was done by the back side (W semicircle) of the tornado vortex. It may have initially broken in a different direction, however, before ending up in this configuration.

17. Site G, looking NE. House debris stacked against trees. These trees acted as an obstacle in the air flow, allowing material to stack against them much as river flood debris stacks against the upstream side of bridge pilings. The fallen limbs still had leaves because they were shielded by the debris stacks. The upright remains of the same trees, in contrast, were stripped leafless. They were shredded by more direct and sustained exposure to tornado winds containing flying debris. There was a wood-frame house unanchored to its cinder-block foundation here; but some of this rubble is also from structures upstream.

18. Site H, looking NE. Destroyed small wood-frame house with slab foundation. No anchoring devices were evident on the foundation. The upside-down vehicle in the rubble (center) was parked in an attached garage or carport just to the left of the red tool box; but the tool box itself was hardly moved. The sheet metal in foreground was of unknown origin.

19. Site I, looking ENE. Overturned truck and damage to grain-processing facility near the S edge of the path. This consists of roof- and partial wall-removal of a wood-frame structure. Dark area at left was an enclosed driveway going through the building.

20. Site I, looking NW. Sheet-metal grain bin removed from foundation. Attachments are evident roughly every 6 feet; but there was only a small amount of grain inside which offered little or no extra support. The bin was blown north and flipped onto its roof. An aerial view (looking WNW) shows the bin (bottom center) was the easternmost of a set of four. The smaller bin at top contained almost no grain and was also removed. The middle two contained more grain; remaining in their locations but sustaining intense deformation. The grain bins were located on the S side of town and the S portion of the damage path. From above, the grain bins are at bottom center when looking N across Spencer, and at top left, when looking SSW.

21. Site J, looking SE. Slab foundation with basement. A wood-frame house was blown away toward the E and NE (left); but no substantial anchoring of house to foundation was evident. The same lot is visible along the upper right edge of this aerial photo, looking WSW.

22-23. Site J, looking NE. Former location of a small, anchored shed. Some of the boards and sheet metal from the shed were deposited in the background tree debris; others became airborne missiles. The bottom of the shed was bolted to metal rods anchored in the ground. These rods were bent toward the E and ENE, the directions most of the shed was blown. The third rod from left is shown in this close-up -- festooned with a piece of insolation from an unknown source. Its bolt was bent slightly under the head (along with the washer), removed from the ring and dropped almost directly underneath.

24-25. Site K, looking NW. SE side of Spencer Fire Station. Though the fire station was completely destroyed, the lack of severe damage or removal of these trucks indicate they were not battered by abundant large debris from a disentegrating firehouse. Also, the gloves at lower right were hardly moved. It appeared as if the fire station was lifted almost intact off its foundation (and away from the trucks) before it disentegrated. Anchor bolts were present; but the anchorage may still have been tenuous anyway. A close-up shot of the area around the gloves shows 1/4" bolts still in the slab foundation. The sill boards at the bottom of the walls popped cleanly off the small bolt heads -- also evident in this view of the NW side of the fire station with the water tower in the background. One remaining piece of sill board on the W side of the firehouse (unseen) was easily removable from its bolt by hand.

26. Site K, looking ENE. Toppled water tower, which apparently went down after its support was undercut by the sedan at center, and/or other substantial airborne missiles. Large debris chunks from the fire station were found around the toppled water tower, and along with the car, may have contributed to its collapse. It is possible that large portions of the fire station was still intact when it reached the tower supports. This aerial view of the water tower and fire station looks SW with the fallen tower at center. A higher view looks W with the fire station at center and the water tower at lower center.

27. Site K, looking SE. Panorama of destruction from within the path core. This was in the eastern portion of the most intense damage (rated F3-F4 by various surveyors), looking roughly along the path in the direction of tornado travel. Trees and homes in this area were extensively battered and shredded by airborne debris from more substantial structures upstream, including the fire station, a bank and an antique store.

28. Site L, looking NNE. Apartment building where the fatalities occurred. Second floor outer walls at front were cleanly removed off the partially underground first floor, with much debris falling down into lower-level apartments. The smoothness and lack of divots along the top of the wall indicates little or no substantial attachment (e.g., pins, bolts) existed between the first and second floors. The tree at right rear was shredded and broken by airborne debris, mostly from the apartment building. The body of a 93 year old woman who lived on the second floor was found under a vehicle N of the building; all five people who perished here were elderly and/or disabled. [The sixth fatality was a healthy 63 year old woman who lived several blocks away.] Other views of this building are shown here.

After all the damage surveys were conducted, the Spencer tornado attained a final consensus damage rating of F4. The NIST report below summarizes their findings and overview of the damage in Spencer.

NIST Damage Survey Report

Damage Rating Exercise

During a presentation on Spencer tornado damage at the Lubbock Severe Weather Conference on Feb 9, 1999, Roger Edwards (SPC) and Greg Harmon (WFO FSD) used examples of the damage to conduct an exercise in rating damage by F-scale. This exercise was performed again with audiences at the National Severe Weather Workshop in Norman (Feb. 2003) and at St. Louis University (Nov. 2003). Go here for more details.

Photo Credits

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