SATELLITE & MESOMETEOROLOGY RESEARCH PROJECT \ \ I \ \ Department of the Geophysical Sciences I \ \ The University of Chicago I \ \ \ \ I \ \ I \ \\ I \ \ I I I I I THE GOTHENBURG FAMILY OF JUNE 18, 1975 I I Gregory S. Forbes I and I Thomas A. Umenhofer I I I I I I I I I I I I

SMRP Research Paper

No. 132 October 197 6 MESOMETEOROLOGY PROJECT • • • RESEARCH PAPERS

1. • Report on the Chicago Tornado of March 4, 1961 - Rodger A. Brown and Tetsuya Fujita

2. • Index to the NSSP Surface Network · Tetsuya Fujita 3. • Outline of a Technique for Precise Rectification of Satellite Photographs • Tetsuya Fujita

4. • Horizontal Structure of Mountain Winds ·Henry A. Brown 5. • An Investigation of Developmental Processes of the Wake Depression Tbi:ough Excess Pressure Analysis of Nocturnal Showers - Joseph L. Goldman 6. • Precipitation in the 1960 Flagstaff Mesometeorological Network · Kenneth A. Styher

7. •• On a Method of Single· and Dual-Image Photogrammetry of Panoramic Aerial Photographs · Tetsuya Fujita

8. A Review of Researches on Analytical Mesometeorology • Tetsuya Fujita 9. • Meteorological Interpretations of Convective Nephsystems Appearing in TIROS Cloud Photographs • Tetsuya Fujita, Toshimitsu Ushijima, William A. Hass, and George T. Dellert, Jr . • 10. Study of the Development of Prefrontal Squall ·Systems Using NSSP Network Data - Joseph L. Goldnian

11. Analysis of Selected Aircraft Data from NSSP Operation, 1962 • Tetsuya Fujita

12. Study of a Long Condensation Trail Photographed by TlROS I • Toshimitsu Ushijima 13. A Technique for Precise Analysis of Satellite Data; Volume I • Photogrammetry (Published as MSL Report No. 14) · Tetsuya Fujita

14. Investigation of a Summer Jet Stream Using TlROS and Aerological Data • Kozo Ninomiya 15. Outline of a Theory and Examples for Precise Analysis of Satellite Radiation Data • Tetsuya Fujita 16. Preliminary Result of Analysis of the Cumulonimbus Cloud of April 21, 1961 - Tetsuya Fujita and James Arnold

17. A Technique for Precise Analysis of Satellite Photographs · Tetsuya Fujita 18. • Evaluation of Limb Darkening from TIROS m Radiation Data - S.H.H. Larsen, Tetsuya Fujita, and W.L. Fletcher

19. Synoptic Interpretation of TIROS ill Measurements of Infrared Radiation • Finn Pedersen and Tetsuya Fujita 20. • Tm.OS m Measurements of Terrestrial Radiation and Reflected and Scattered Solar Radiation - S.H.H. Larsen, Tetsuya Fujita, and W. L. Fletcher

21. On the Low-level Structure of a Squall Line • Henry A. Brown

22. • and the Low-level Jet - William O. Bonner

23. • The Mesoanalysis of an Organized Convective System - Henry A. Brown

24. Preliminary Radar and Photogrammetric Study of the Illinois Tornadoes of April 17 and 22, 1963 · Joseph L. Goldman and Tetsuya Fujita

25. Use of TIROS Pictures for Studies of the Internal Structure of Tropical Storms -Tetsuya Fujita with Rectified Pictures from TIROS I Orbit 125, R/0 128 · Toshimitsu Ushijima 26. An Experiment in the Determination of Geostrophic and Isallobaric Winds from NSSP Pressure Data - William Bonner 27. Proposed Mechanism of Hook Echo Formation - Tetsuya Fujita with a Preliminary Mesosynoptic Analysis of Tornado Cyclone Case of May 26, 1963 • Tetsuya Fujita and Robbi Stuhmer

28 . The Decaying Stage of Hurricane Anna of July 1961 as Portrayed by TIROS Cloud Photographs and Infrared Radiation from the Top of the Storm · Tetsuya Fujita and James Arnold 29. A Technique for Precise Analysis of Satellite Data, Volume II - Radiation Analysis, Section 6. Fixed-Position Scanning· Tetsuya Fujita 30. Evaluation of Errors in the Graphical Rectification of Satellite Photographs - Tetsuya Fujita 31 . Tables of Scan Nadir and Horizontal Angles - William D. Bonner

32. A Simplified Grid Technique for Determining Scan Lines Generated by the TIROS Scanning Radiometer ·James E . Arnold

33. A Study of Cumulus over the Flagstaff Research Network with the Use of U-2 Photographs - Dorothy L. Bradbury and Tetsuya Fujita

34. The Scanning Printer and Its Application to Detailed Analysis of Satellite Radiation Data • Tetsuya Fujita

35. Synoptic Study of Cold Air Outbreak over the Mediterranean using Satellite Photographs and Radiation Data - Aasmund Rabbe and Tetsuya Fujita

36. Accurate Calibration of Doppler Winds for their use in the Computation of Mesoscale Wind Fields - Tetsuya Fujita

37. Proposed Operation of Intrumented Aircraft for Research on Moisture Fronts and Wake Depressions - Tetsuya Fujita and Dorothy L. Bradbury

38. Statistical and Kinematical Properties of the Low-level Jet Stream - William D. Bonner 39. The Illinois Tornadoes of 17 and 22 Apr il 1963 - Joseph L. Goldman

40. Resolution of the Niml::us High Resolution Infrared Radiometer - Tetsuya Fujita and William R. Sandeen

41. On the Determination of the Exchange Coefficients in Convective Clouds - Rodger A. Brown

• Out of Print •• To he published (Continued on back cover) THE GOTHENBURG OF JUNE 18, 1975

by

Gregory s. Forbes and Thomas A. Urnenhofer The University of Chicago

SMRP Research Paper Number 132 October 1976

This research has been performed under the U.S. Nuclear Regulatory Commission, Off ice of Nuclear Regulatory Research, Contract No. E(ll-1)-2507, and renewal Contract No. AT(49-24)- 0239. THE GOIBENBURG TORNADO FAMILY OF JUNE 18, 1975

Gregory S. Forbes and Thomas A. Umenhofer Department of tlie Geophysical Sciences The University of Chicago

Abstract

The survey was prompted by reports of a 9()-mile-long (145 km), skipping tornado path. The survey con.finned that the damage was produced not by one skipping tornado, but rather by a .family of eight separate tornadoes. The distance from the beginning of the first tornado to the end of the eighth tornado was 106 miles (171 km). At times, more than one tornado was on the ground simultaneously, resulting in a total path length of the eight tornadoes of 131 miles (211 km). Therefore, what was reported as a skipping tornado was really on the ground 1243 of the distance between first and last damage.

The most remarkable damage found was a large hole in the grmmd, roughly 10 feet by 6. 5 feet (3m by 2m) and up to 18. 5 inches (47 cm) deep. Dirt was scattered in piles to the north-northeast of the hole, but about 503 of the mass removed from the hole was missing. It is probable that this hole and related ground disturbances nearby were the combined effects of and a tornado or suction vortex within the tornado at that location. Similar phenomena observed in the past are tabulated.

Specific examples of damage are presented. Large objects were blown and bounced for great distances. Suction swaths were observed in several of the tornado paths. The new evidence from this survey em'(il.asizes the complexity of tornado phenomena. 2

1. INTRODUCTION

The Gothenburg survey was prompted by reports of a 90-mile-long (145 km), skipping tornado path between Bartley and Arnold, Nebraska, occurring in the late afternoon and evening on June 18, 1975. Furthermore, the public reported seeing numerous funnels. Based upon this information, a survey was performed to investi­ gate ( 1) the nature of a reported "skipping tornado" and ( 2) the details of the tornado damage pattern. Results of the study of the damage pattern are presented in Section 3.

The aerial survey of the Gothenburg area revealed that a family of eight tornadoes 1 had occurred. The tornado paths were in such clo~e proximity to on~ another that, from scattered reports of damage, one could incorrectly interpret that the damage was from one skipping tornado. Figure 1 shows the tornado family damage paths. The Gothenburg tornado family is discussed in Section 2.

The authors were fortunate to find spectacular damage while performing a ground survey of the Gothenburg family tornado damage. While looking for pictures of the tornadoes, the author~ talked to Mr. Gene Hoppe of Farnam. He took us to a field owned by Mr. Orie Pursel. Much, to our amazement, we saw a large hole in the ground, with ste~p sides and a relatively flat bottom. Dirt was scattered to the north-northeast beyond the hole. Next to the hol~ was a huge crack, where the soil layer was elevated, but insufficiently removed to fo:pn a large hole. These features are shown in overview in Figure 2.

1When the ftlll path information, F PP estimates, and damage descriptions were. supplied to the National Weather Service, Storm Data listed the event as a tornado family with 106 mile (145 km) length, composed of eight tornadoes. Refer .to Storm Data (1975). Had this survey not been performed, it is likely that the official listing would have been that of the original report, a "skipping tornado". 3

GOTHENBURG TORNADO FAMILY 18 JUNE 1975

0 l! 10 20 30 MILES 11111111111 I I r

NORTH.. PLATTE

Figure 2. Reference view of the holes within the path of the Moorefield holes 14-\ FARNAM v tornado. Looking northward, the f>IOOllEFIELO V --13 hole is in the foreg.i-01.md, the huge 12-/3A crack is behind and slightly left of the hole, and dirt piles extend north­ "'"""' eastward from the holes. A wind­ ~ mill was blown to the location in the

l!IARTLEY Y background.

MC COOK ( •

\DANBURY Y

Figure 1. The eight tornadoes of the (Note that in this and all other draw­ Gothenburg family. Numbers refer ings, the left and right edges are to figures in this pa.per, showing in­ aligned north - south. ) teresting damage at these locations.

Figure 3 shows a closeup of a portion of the side of the hole. The force that removed the dirt failed to remove roots, which were sticking up from the bottom of the hole. After considering the importance of finding these holes, the authors returned· to thoroughly measure and document them. Results of these measurements are presented in Section 4. 4

Figure 3. Close-up of a portion of one side of the hole. A root extends out of the bottom of the hole. ·

2. THE GO'IHENBURG FAMILY TORNADOES

Aerial surveys were performed on ]lllle 22 and June 23, 1975 and revealed that an interesting family of eight tornadoes had occurred. The distance covered by this family, from the point of touchdown of the first tornado to the point of liftoff of the eighth tornado, was 106 miles (171 km). The combined length of the eight tornado paths was longer than this "family length" because tornadoes formed at locations east of existing tornado tracks in a parallel mode (refer to Fujita et. al. , 1970). The combined length of the eight paths was 131 miles (2ll km); 124% of the "family length".

Skipping Tornado V~rsus Tornado Family

Because the Gothenburg tornado family was originally reported as a skipping tornado with a 90-mile (145 km) path, a serious concern is raised about the use of tornado reports in assessing tornado risk. There should naturally be a lower risk based upon a skipping tornado than upon a non-skipping tornado of equal length, because the skipping tornado is on the· ground less than 100% 5 of the time. However, if the "skipping tornado" is really a tornado family, it is not necessarily covering less than 100% of the reported distance (as shown above), and the risk should not necessarily be lower than for a continuous tornado. Reports of skipping tornadoes are not uncommon. There is uncertainty regarding the reality of the phenomenon, however. Part of the reports of skipping tornadoes could arise because farms are often several miles apart, resulting in reports that damage is intermittent. Other reports of skipping tornadoes could result from observation of several paths of separate tornadoes in succession, a tornado family.

A tornado family is a sequence of tornadoes produced from a single thunder­ storm. As more tornado occurrences are studied, it becomes apparent that tornado families are common. Fujita (1963) and Darkow (1971) listed nwnerous occurrences of tornado families. But the April 3, 1974 tornado outbreak provided an even more spectacular example. Research performed on the April 3, 1974 tornado outbreak led meteorologists at the University of Chicago to believe that tornado family production from a tornadic may be the rule rather than an exception. Fujita and Forbes (1974) found that 743 of the tornadoes in that outbreak occurred in families. Thirty families were found. Thus, when one strong tornado occurs, it is very likely that as it dissipates it will be succeeded by a new tornado.

Whereas tornado families are found to be common, aerial surveys performed by the University of Chicago, such as Fujita (l 975b), show that long, skipping tornado paths are quite rare. From the air, the tornado path can often be detected from dis­ turbances of certain types of vegetation, not observable from the ground. Because ground surveys mostly confirm structural and tree damage near roads, ground-based observers are more likely to report that tornadoes skip. Aerial surveys show that

tornadoes produce damage continuously, although not always of the same intensity, even when observers say the funnel appeared to skip up and down.

In view of the use of tornado reports to assess tornado risk, meteorologists should exercise caution in reporting that a tornado skipped. Similarly, users of tornado reports must use caution in interpreting "skipping tornadoes". 6 Details of the Gothenburg Tornado Family

Table 1 classifies the intensity, path length, and path width of the tornadoes by F PP, the Fujita - Pearson scale. The Arnold tornado was strongest at F 4. The only fatality occurred in this tornado: a woman killed when the pickup truck in which she was riding was blown off the road. The Peterson, Moorefield, Farnam, Gothenburg, and Stockville tornadoes were. all cJassified as F 3. The Bartley and Danbury tornadoes were significantly weaker at F 1.

The tornado family resulted from successive formations of new tornadoes, typically several miles to the east of the previous tornadotrack, as the thunder­ storm moved northward. Tot Holmes of the Tri-City Tribune and nwnerous others reported seeing several funnels both simultaneously as well as in succession. At times, it was reported that, away from the tornado, small funnels unsuccessfully attempted to form beneath the thunderstorm.

Holmes was able to photograph two separate tornadoes. In addition, Scott Hess photographed a third tornado. In Figure 4, these photographs of the Peterson, Farnam, and Moorefield tornadoes show that although all were part of the same family, their appearance and shape were quite different. At the time of the pictures, the Peterson and Moorefield tornadoes were producing F 2 damage and the Farnam tornado was producing F 0 damage at the locations shown in Fig. 1.

Tornado (length) F PL PW

Danbury (10 mi/ 16 km) 1 2 4 Bartley (15 mi/ 24 km) 1 3 3 Stockville (14 mi/ 23 km) 3 3 3 Moorefield (17 mi/ 27 km) 3 3 3 Farnam (21 mi/ 34 km) 3 3 2 Gothenburg (10 mi/ 16 km) 3 3 3 Peterson (29 mi/ 47 km) 3 3 4 Arnold (15 mi/ 24 km) 4 3 3

Table 1. Classification of the Gothenburg Family Tornadoes. 7 A tornado often changes shape and appearance with time in response to the type of surface it crosses and its acquisitions of water vapor, dust, and debris into its circulation. The two tornadoes photographed by Holmes were consistently of different appearance, however. He referred to the Peterson tornado as "the big one" in com-

Figure 4. Photos of three tornadoes of the Gothenburg family. A: Hess photo of the Moorefield tornado; B: Holmes photo of the Farnam tornado; C: Holmes ];iloto of the Peterson tornado. Locations are shown in Fig. 1. (Photos repro­ duced courtesy of Mr. Scott Hess and Mr. Tot Holmes.) 8 parison with the Farnam tornado. Therefore tornadoes in a family are not necessarily similar in appearance. The production of tornadoes in a tornado family usually occurs in a regular · manner, with a fairly uniform period of time between formation of successive tornadoes. While Fujita (1963) and Darkow (1971) found that this period averages about 45 minutes , different thunderstorms may exhibit different periods. The average period for the April 3, 197 4 family tornadoes was 40 minutes, with extremes of 14 and 80 minutes. The intervals between tornadoes in the Gothenburg family were scmewhat irregular and less than normal, however. Using reported times of tornado occurrences and interpolation based upon the Grand Island radar, which showed the thunderstorm moving northward at 29 mph (13 ms -l), the average period was 29 minutes, with extremes of 11 and 41 minutes, between successive touchdowns.

Fujita (1975a) demonstrated that the movement of the tornad~ can differ frcm that of the parent thunderstorm. As seen in Figure 1, the Danbury, Stockville, and Arnold tornadoes made pronounced left turns after their initial

northward movement. In addition, the othe~ tornadoes moved rather consistently toward the north ..:northwest, to the left of the direction taken by the parent thtmderstorm. The parent thunderstorm which spawns a tornado family often takes a hook-like shape on radar. Forbes (1975) found_that 813 of the tornadoes in his radar study of the April 3, 1974 tornadoes occurred fr9m hook-like echoes, including all F 4 and F 5 tornadoes and nearly all tornado families.

The NWS radar at Lee Bird Field at North Platte showed.a hook echo during the Peterson tornado. Figure 5 combines the radar echo sketch made by Harry Spohn of the NWS with the damage path. At this time, the tornado was located just inside the hook. It was very forttmate that while Mr. Spohn was observing the hook echo, Mr. Holmes was }ilotographing the tornado. In Holmes' }iloto, Figure 4C, little imagination is required to visualize the hook echo aloft in the foreground, with the tornado in the background. Holmes reported sporadic hail and strong gusts as he }ilotogra}iled from beneath the hook. Shortly after the photo was taken, these downdrafts damaged several farm buildings several niiles t6 the north of his location. 9

L _~o~ _c o_. ___

L I NC OLN CO .

RAOAR ECHO

FROM

SKETCH BY STRAIGHT W IND DAMAGE

Ii . SPOHN ,

~ ~\ ._...-- io ..>-- ...,,..., c:.___ 0 .- .------·- t---=-~·---

CUSTER CO .

0 I I I I I Ml .

Figure 5. Hook echo asso~iated with the Gothenburg family. The radar sketch by Harry Spoon, MIC of the North Platte National Weather Service Office, is com - bined with the track determined by aerial survey.

3. DAMAGE REVEALS nIREE SCALES OF MOTION

Although damageable structures are more scarce, there are advantages in studying tornadoes in rural areas. First, suction vortices mark out their presence most clearly in certain vegetated fields. Second, the sources and paths of debris carried for long di.stances are more easily identified. These advantages enable the scientist to more readily understand the wind field accompanying the tornado. Evi­ dence is fmmd that damaging winds occur on the suction vortex scale, on the tornado scale, and on the tornado cyclone scale.

In this section, examples of surface marks and examples of bouncing and blowing debris are given. The location of the damage described in these examples is shown in Figure 1. 10 --I~-~

A B

.I .2 .3 .4 .l! Ml I I I I I I I I I I I .2 .4 .6 .8 KM I

Figure 6. Suction swaths in the Fa;rnam tornado. A. Aerial photo. B. Rectified analysis of damage. Trapezoid shows area covered by aerial photo A.

Surface Marks

The Farnam tornado was surprising in that after passing over an area virtually devoid of damageable material, and creating minor damage in the few miles prior to Figure 6, the tornado suddenly devastated the John McWha farm. Buildings were destroyed, trees levelled, and knee-high com damaged. Mr. McWha saw the tornado, describing its appearance to be like that of a large dust devil with small ftmnels in it. These small fwmels, suction vortices, produced the swaths of Figure 6.

Calculations based upon the shape of the swaths yield a tornado windspeed of -1 . -1 about 100 mph (45m s ). Adding a value of 60-100 mph (27-45m s ) to represent the wind circulation of the suction vortex, the maximmn windspeed at the McWha farm . -1 was about 160-200 mph (72-89m s ). It should be noted that the suction vortex

circulation estimates in this section are conservative. Above the boundary lay~r, the -1 speed could be 157 mph (70m s ), as measured by Forbes (1976). 11 The overall tree damage was over an area wider than the diameter of the suction swath pattern, indicating tornadic winds extending beyond the radius where the suction vortices moved about the tornado. F 3 damage, however, consisted of the heaviest' tree damage and the building damage, in line with the suction swath path. This fact clearly defined the F 3 damage area as being confined to the area traversed by suction vortices, with weaker damage elsewhere caused by wind within the other­ wise weak tornado.

\ f < ~ -- -\-- - -1 \ \ ..... 1 I \~ ,~ -... L I I ..... I \ I --. , ~ 1\'\ I I I I I : I - --\ \,- - ,I - -1- ..,l?rnad o I \ Pat hl I I

.I .2 .3 .4 .5 Ml I I I I I I I I I I I . 2 .4 .6 .8 KM I

Figure 7. Suction swaths in the Gothenburg tornado.

Figure 7 shows suction swaths in a different pattern, in the Gothenburg tornado. The difference in shape between the swaths of Figures 6 and 7 implies ·that the speed of revolution of the suction vortices about the tornado was slower in the Gothenburg tornado. (For a given tornado translation speed, the loops are larger and more circular when the suction vortex revolves fast around the tornado.) This is consistent with the fact that at this point (near the beginning of the tornado) the Ruben Braten farm experienced only minor damage. nus is because the suction vortices missed the farm structures, as shown by the swaths in Figure 7. Mr. Braten observed what he called a dust cloud as the tornado approached. 12 At the Braten farm the tornado windspeed was calculated to be only about 75 mjil (33m s -l). Adding 60-100 mph (27-45m s -l) for the suction vortex wind circu­ 1 lation gives a maximum windspeed of 135-175 mph (60-78m s- ) at this location.

The Peterson tornado left well-shaped suction swaths in a cornfield, at the locations shown in Figure I. The maximum windspeed is estiffiated to have been

200 mph (89 ms -l) there. Of a more unusual nature was ·the lineation mark that the tornado left in the field shown in Figure 8. The slight discoloration of the prairie surface, making the tornado path visible, was due to a thin deposit of dirt picked up by the tornado while crossing the open field.

\ \ \ \ \ \ \ \ --\ \ \ \ \ \

\ I ' I \ I \ \ \

.I .2 .3 .4 .5 I I I I I I I I I I I .2 .4 .6 .8 ::I

Figure 8. Swath of di.rt deposited by the Peterson tornado. 13

A Suction Swa th a B

. I .2 .3 .4 .5 Ml I I I I I I I I I I I .2 .4 .6 .8 KM I Figure 9. A. Hay swaths in the Arnold tornado associated with tornado cyclone wind. B. Rec­ tified analysis of damage. Trap­ ezium locates photo A. The other swath was due to weak suction vortices.

The Arnold tornado exhibited a pattern of weak, wide swaths shown in Figure 9B. The hay shown in Figure 9A was apparently blown northeastward after the trees were knocked down from the northeast, because the hay pattern was not disturbed near the trees. This southwesterly wind, blowing the hay and doing other minor damage, occurred slightly outside the tornado pa.th. Apparently it was associated with the tornado cyclone.

Blowing and Bouncing Debris

Light debris can be blown for miles by tornado-strength winds. Even heavy objects , however, can be blown and bounced fo1 long distances if their surface area is large enough. One type of structure which is commonly affected is a grain bin built from thin galvanized steel sheets. The connection to a concrete base does not withstand the tornado windspeeds, allowing the metal bin to be blown and bounced away, Often the large bin breaks up into several pieces. 14 BLOWING AND BOUNCING DEBRIS

Distance Description Movement Mi/km Stockville Tornado 1. Hay blown .12/.19 Toward NW 2. Grain bin bounced .30/.48 Toward NW 3. Trees blown .05/.08 In loop N - s - SE 4~ Boards of barn blown .05/.08 In loop E - N Moorefield Tornado 1. Grain bin bounced (Fig. 12) .33/.53 In loop s - E· - NE 2. Combine slid • 02/. 03 Toward NNE 3. Grain bin bounced .14/.23 In loop E - NE 4. Boards blown .25/.40 In loop N -w - s S. Grain bin blown (Fig. 13) .68/1.09 In loop s -E - N - NNW 6. Grain bin bounced (Fig. 13) .14/.23 In loop S - E - NE 7. Boards of barn blown .09/.14 Toward S 8. Trees blown (Fig. 14) .05/.08 Toward N Farnam Tornado 1. Hay blown (Fig. 6) .08/. 13 Toward N Gothenburg Tornado 1. Grain bin bounced .18/.29 In loop N - W 2. Grain bin bounced (Fig. 10) .25/.40 Toward NNW 3. Grain bin bounced (Fig. 10) .86/1.38 Toward NNW 4. Boards blown (Fig. 10) .06/.10 In loop NW -w 5. Grain bin bounced .25/.40 Toward N , Peterson Tornado 1. Dirt blown (Fig. 8) • 76/1. 22 Toward NNW 2. Boards blown .24/.39 Toward NNE 3. Boards blown .41/.66 In loop W - SW Arnold Tornado 1. Boards blown (Fig. 11) .11/ .18 In loop SW - s - SE 2. Combine slid (Fig. 11) .10/.16 Toward N 3. Combine bounced (Fig. 11) .16/.26 Toward NNE 4. Hay blown (Fig. 9) .23/.37 Toward NE

Table 2. Distances travelled by blowing and bouncing debris in the Gothenburg family tornadoes. Only objects visible from the air, whose source and path were clearly distinguishable, are included. In the event that an object broke into several pieces, only the distance of the farthest detectable piece is listed. 15 Table 2 lists the distances travelled by various blowing and bouncing debris seen in the aerial survey of the Gothenburg family. The farthest distance the debris travelled was • 86 miles (1. 38 km), in a nearly straight line. This debris which was blown the farthest was a grain bin from the Walgren drying and storage complex, shown in Figure 10. Three pieces of debris went through the field, in basically a straight line. It app~rs that the bins moved roughly parallel to the tornado movement, somehow carried with the tornado as they bounced and rolled along the ground. The paths of the two pieces of debris blown the farthest actually crossed. By contrast, the debris at the next farm to the north of the Walgren complex was blown in a swirl toward the west.

.I .2 .3 .4 .5 Ml I I I I I I I I I I I ··;.. ~ . - .2 .4 .6 .8 KM . ~ .. t' I

Figure 10. Bounce marks indicate the path taken by grain bins blown by the Gothenburg tornado. 16

A

8 c Tornado 1--- Path ---

.I .2 .3 .4 .5 1111 I I I I I I I I I I I .2 .4 .6 .8 Kiii I

Figure 11. Devastation of the La Verne Barnes farm in the Arnold tornado. A. Overview showing farm machinery carried into and through a stand of trees. The original location (0), and the final location of the large combine (L) and the smaller combine (B, shown in Fig. llB), are indicated. B. · Combine carried .10 mile ( .16 km) through the stand of trees. C. Rectified analysis of damage. Barn debris was blown in a spiral to the south. 17 The huge farm implements at the La Verne Barnes farm shown in Figure 11 were many times more dense than grain bins. The largest machine in the stand of trees was a combine weighing 18, 500 pounds, and was transported .10 miles (.16 km). The machine on the slope beyond the trees, Figure llB, was also a combine, weighing slightly less. It travelled . 16 miles (. 26 km).

.I .2 .3 .4 .5 Ml I I I I I I I I I I .2 .4 .6 .8 KM I

Figure 12. Grain bin bounced southeastward in the Moorefield tornado.

The Moorefield tornado appeared to contain suction vortices . Although the tornado was far away and therefore hard to distinguish, the tornado photo in Figure 4A s uggests the existence of suction vortices in the lower portion of the tornado. One of the suction vor tices could have been responsible for the damage shown in Figure 12. One of several grain bins blown in large loops toward the southeast by the Moorefield tornado, this bin was bounced for . 33 miles ( . 53 km). At this tfme the overall tornado did not appear to be particularly strong, with the farm experiencing only minor damage. 18 At the Rex Ealy farm, debris was scattered over a large area. There were indications in the field of southward-moving suction vortices. A grain bin was destroyed and blown in a large loop, shown in Figure 13. Parts of the bin were deposited southeast, east, and northeast of the original "location of the bin. One piece travelled • 68 miles (1. 09 km). Another bin was blown through a pond and then to the northeast.

A close study of the shape of the loop in Figure 13 indicates a subtle problem concerning the tornado structure: the oblong loop, representing the trajectory of the grain bin, went too far southward in comparison to the east-west diameter of the loop. This southward excursion probably represents ejection away from the tornado center. It is not known what caused the debris to recurve northward.

SMAL L DEBRIS

.I .2 .3 .4 .5 Ml I I I I I I I I I I .2 .4 .6 .8 KM I

Figure 13. Grain bin blown in a loop in the Moorefield tornado. 19 4. 1HE MOOREFIEID HOLES

The damage shown in Figure 14, from the Moorefield tornado, was not particu­ larly spectacular. However, the swath of tree damage was strong, with trees uprooted, broken, and blown away. The swath of broken trees reached the road, and large limbs were carried even farther.

The importance of the damage in Figure 14A is that . 12 miles (. 2 km) north of

this location, holes were found in the ground~ Just north of the holes, a tree and a windmill were dragged in a circle, leaving scratches on the ground. Thus, the damage places the holes in the direct path of the tornado, as shown in Figure 14B.

/Ljj A \JJL;;i B 0 . 10 . 2 0 Ml . I I I I I I 0 JOO 200 300 4 00 M.

Figure 14. A~ Swath of damage in the Moorefield tornado. B. Topographic map in the vicinity of the hole location. Heavy lines represent the 2800 foot (853m) contour and the 2700 foot (823m) contour. Contours are at 20 foot (6m) intervals. 20 There was no indication that the holes had been related to some large object bouncing in that vicinity: no large scratches or remnant debris were found and the owner and local re8idents knew of no such missile. The owner and the local residents guaran­ teed that the holes were not man-made: they felt that the holes were created by the tornado.

0 I 2 3 4 5 M 1 1 I I" 1' 1"1 I I I I I I I 0 1 2345 10 15 FT

Figure 15. Contours of the holes,_in centimeters, at 10 cm intervals. The zero reference contour represents 835 m (2740 feet) above sea level. Shaded areas are'grass-covered. As in the other drawings, the left and right edges are aligned north-south. 21 Documentation of the Holes

In order to obtain scientific information, detailed measurements were taken. Level lines were laid out at 1 meter intervals in order that the depth of the hole could be measured at numerous locations. The results of these measurements are shown in Figure 15. The contours shown are drawn with respect to the zero reference level; which corresponds to 2740 feet (835m) above sea level.

Figure 15 shows the relative locations. of the features investigated. The large evacuated area, shown in Figure 2, is referred to as the "hole". The large trough, about 16 feet (5 m) north-northwest of the hole, shown in Figure 16, is referred to as the "huge crack". About 13 feet (4 m) east of the hole is what is called the "overthrust", shown in Figure 17. To the west of both the hole and huge crack were numerous smaller cracks. Dirt was deposited in clumps north to northeast of both the hole and huge crack.

Figure 16. lb.oto of the holes. The huge crack is in the foreground. The hole is in the background, to the south-southeast. 22 The "huge crack" and the ''hole" are the holes referred to in the heading of this section. The ''huge crack" was given that name merely for reference in this paper. fhysically, it appears to represent a stage of formation of a more distinct hole.

The hole measured about IO x 6. 5 feet (3 m by 2 m). At the previous surface 2 2 level, the total area of the hole was 67. 5 ft (6. 27 m ). The hole typically had sloping sides, although at some places its sides were nearly vertical (see Figure 3). Due to the sloping sides, the mean depth of the hole was 11. 8 inches (30 cm). The deepest 3 portion of the hole was 18. 5 inches. (47 cm). The total volume of the hole was 66. 75 ft 3 (1. 89m ).

The overthrust area was composed of a block of soil which had slid over the top of the block of soil to the east. Figure 18,A is -a cross-section (exaggerated in the vertical) showing the extent of the "fault" region. Tilis thrust fault extended at least 12 inches (31 cm) along an angle of 50 degrees from horizontal.

Figure 17. Photo of the overthrust, viewed from the east. The hole is in the background. 23

+40 CM OVERT HR UST

+40 CM

Figure 18. Cross-sections of the holes, exaggerated in the vertical. (Vertical : horizontal = 2. 5 : 1 ) A. Cross section through the hole and overthrust. B. Cross section thrrugh the hole and a small crack to its west. C. Cross section through the huge crack and a small crack to its west. Cross sections . are oriented west (left) to east (right), at the locations shown in Fig. 15. 24 The huge crack seems to illustrate the maruier in which the dirt was ta.ken out of the ground. It was apparently removed in a layer, which subsequently broke into chunks. As seen in Figure 16 and Figure 18C, the west edge of the layer was lifted out of the ground, while the east portion remained relatively stationary. Other dirt then blew wider or collapsed under the elevated west end of the layer, allowing it to remain above the former surface level.

The deepest part of the huge crack was 11.4 inches (29 cm) below the former surface. The top of the elevated layer was up to 16 inches (41 cm) above the former 3 3 surface. The volume of the huge crack was 9.18 ft (. 26m ).

The dirt layer was apparently broken into chunks during the process of evacua­ tion from the ground. These chunks skidded or bounced along the ground, coming to rest north to northeast of the holes. No sizeable chunks (roughly larger 3 3 than • 02 ft (500 cm ) or 1.1 lb (. 5 kg) ) were observed more than 36 feet (11 m) from their origin. These chunks comprise the dirt piles shown in Figure 15. When measured, the density of the soil formerly occupying the suction hole was -3 -3 122 lb ft (1. 95 g cm ). Thus, the hole previously contained 8126 lb (3686 kg) or 4. 06 tons of dirt. The huge crack contained 1118 lb (507 kg). The soil was fairly dry when measured. If it was wet at the ti.Itle of the tornado, the weight would have been even more. It is also likely that the dirt in the hole was more consolidated (denser) than the sample used to obtain the density.

When the volume of the dirt deposits northeast of the hole and huge crack were calculated, they failed to account for all of the dirt removed. 503 of the volume of the huge crack and 563 of the volume of the hole were deposited. It must be noted that these percentages represent dirt completely removed from the ground. The elevated layer on the east edge of the huge crack was no.t counted. These volume fractions do not necessarily represent mass fractions. If there was a significant loosening of the previously consolidated layer, the density of the dirt in the piles would decrease. The piles consisted mainly of large chunks of consolidated dirt, however. Thus, it is expected that the volume fractions only slightly over­ estimate the percentage of mass deposited in the dirt piles. 25 About 50%· of the dirt completely removed from the ground has, therefore, not been accounted for. Perhaps it was ingested into the tornado and gradually deposited in a thin layer, as in the Peterson tornado mentioned previously (see Figure 8). Since the Peterson tornado had a dirt source with larger surface area, its path of de.posited dirt could be seen from the air.

There was a series of small vertical cracks to the west of the suction hole. Figure 18B shows a cross section of the suction hole and one of the cracks. These small cracks appeared to be caused by or associated with the dirt removal, rather than a factor in facilitating its removal.

Possible Explanation of the Formation of the Holes

At this point, the holes have been documented. It remains to explain their forma­ tion. Similar phenomena have been reported in the literature. Selected cases are discussed below, and all cases known to the authors are compiled in the Appendix.

Oliver (1931) reports that in the Gothenburg, Nebraska tornadoes of June 24, 1930, "grass and shrubs were torn out by the roots, leaving the earth bare. In places, even the earth was gouged out. " Gray (1964) reports that a Marion, Mississippi tornado on April 5, 1964 "pulled the sod up, and exerted such force that huge cracks were forced open in the sod in an area about 10 ft (3 m) in diameter. " The tornado also "ripped huge chunks of soil and grass down to a depth of 8 inches (20 cm) in an area 20 feet (6m) wide and 50 feet (15m) long." Fujita et al. (1970) mention lawns dug up in the Greentown, Indiana area during a tornado in the Palm Sunday outbreak of April 11, 1965.

There appears to be another possible explanation for the phenomenon. A colleague, Edward W. Pearl, suggested that lightning was a distinct factor for con­ sideration.

There are numerous accounts of tmusual electrical phenomena near tornadoes (see, for example, Vonnegut and Moore, 1959). There are also cases in the literature where lightning has caused cracks, and even holes, in the ground. Viemeister (1972) explains this occurrence in terms of heating and expansion of air trapped within the soil as lightning passes through the soil. 26 A hole 7 to 12 feet (2. 1 to 3. 7 m) in diameter and a foot (. 3 m) deep was reported near Leland, Illinois on April 2, 1959 by Bnmk et al. (1959). The cause of this irregu­ larly-shaped hole was attributed to a severe stroke of lightning. A different type of hole was found near Dodge, Nebraska, following a thunderstorm on June 24, 1935 Qensen, 1936). This hole was over 15 feet (4. 6m) deep, and only about 8 inches (3.1 cm) in diameter at the surface. Dirt was scattered from all sides of the hole. Vonnegut and Moore (1959) report holes found along the path of the Fargo, N. D. , tornado of June 20, 1957. There were numerous holes in the turf of a golf course, ranging in size from 6 to 24 inches (2. 4-9. 5 cm). In one instance the turf was rolled up into a ball for a distance of 4 feet (1. 2m). Although these features were in the direct path of the funnel, some were thought to have been made by lightning, as the grass seemed seared at the sides of the holes.

In some cases, the effects of lightning on the ground have been explosive. Miiller-Hillebrand (1963) reports an occurrence where lightning travelled 115 feet (35m) through the soil, causing several cubic meters of earth and stones to be thrown up. Six windows of a house along the undergr0tmd lightning path were broken and 3 1. 4-1. 8 cubic feet (. 04 or • 05 m ) of earth and stones were thrown into the upper floor of the house. Falconer (1966) reports that in Troy, New York on July 9, 1960, lightning struck a parked school bus and jumped to the ground via the wheel rims and the tail­ pipe. The asphalt pavement was dug up in a zig-zag pattern of channels up to 2. 5 inches (6 cm) deep, 2 to 8 inches (5-20 cm) wide and up to 10 feet (3m) long. Several pieces of the asphalt landed on top of the 11-foot-tall (3. 3m) bus.

The literature, therefore, suggests two possibilities for the mode of origin of holes in the ground which are apparently produced as a result of atmospheric forces: tornado-produced and lightning-produced. To these should be added the possibilities that lightning acted in combination with wind or in combination with a vortex.

One would expect the resultant holes and dirt scatter to vary, depending on the mode of origin. In the case of a lightning hole (L hole), one would expect uniform scatter of dirt in all directions, in the absence of strong wind. With strong wind at the time of the lightning, one would expect dirt to be scattered downwind of the 27 lightning/wind hole (L/ W hole) in a basically straight line. When lightning and a vortex are both involved, it is expected that dirt from the lightning/ vortex hole (L/V hole) would normally be deposited in a curved path or a swirl. Furthermore, loose and cracked soil layers might be expected to be blown away in the presence of tornadic winds.

An eirample of each type of hole can be found in the literature discussed above. The Dodge, Nebraska case appears to be an example of an L hole. Further investiga­ 2 tion by Fujita led him to believe that the Marion, Mississippi case is an example of an L/ W hole. The Fargo case appears to be an example of an L/ V hole. It is con­ cluded later in this paper that the Moorefield holes were L/ V holes.

It is difficult to imagine how a tornado, through some combination of wind and pressure, could remove dirt from an tmdisturbed surface. Nevertheless, attempts were made to estimate the windspeed necessary to produce a hole in the grolllld. One approach was to estimate the pressure force necessary to suspend the dirt against gravity. Another approach was to estimate, through analogy to soil shear-strength tests in soil mechanics, the windspeed necessary to crack the soil. These approaches 1 gave necessary windspeeds of about 246-291 mph (110-130m s- ) at grass level. This was hard to accept, in view of the requirement that horizontal velocity must be zero at the surface, because of friction. In addition, the grass in the vicinity of the holes did not appear to be torn or uprooted, as one would expect if winds somehow were exceptionally strong near the ground.

Based upon these objections, it appears that the tornado, acting alone, could not have created the holes from previously tmdisturbed grotmd. If initially there were imperfections in the soil layer, such as horizontal and vertical cracks or weak­ nesses, then the task of removing the soil would be more simple. Such initial imper­ fections could have occurred due to numerous factors, including geologic processes, animal burrows, and lightning.

2 Personal communication, 1976. 28 The lightning mechanism is plausible, considering the close proximity of the holes and the number of cracks in the vicinity. However, the grass showed no signs of scorching and no fulgurites (fused sand) were found. The relative flatness of the bottom of the hole is somewhat perplexing, if lightning was the chief mech­ anism. Because the site is relatively isolated, it is not known whether lightning struck there. It has been mentioned that the dirt is often thrown about with explosive force when lightning strikes the ground. In the absence of wind, one would expect a scatter of dirt in all directions. All of the dirt was found to the north-northeast of the holes, however. There must have been a south-southwesterly wind which at some time transported the dirt away from the holes.

Asswning that the dirt transport was accomplished by the tornado, one is tempted to assume that the dirt was exploded from the hole. This may very well explain the loss of 50% of the dirt from the hole, in terms of dust and small chunks of dirt carried away by the tornadic winds.

With regard to the chunks of dirt deposited north-northeast of the holes, however, it appears that the word "explosion" is too dramatic. An explosion would have sent dirt flying into the air. In the presence of a wind strong enough to cause all chunks to be deposited to the north-northeast, the chunks would not have landed so close to the hole as was omerved. It was concluded that rather than becoming truly airborne, these chunks slid or bounced along the earth's surface.

It seems plausible that a suction vortex and lightning acted in combination in forming the holes. A suction vortex is specified because of its known ability to trans - port and accumulate material along the ground, which would accomplish the dirt removal. The time interval between the lightning stroke and the passage of the suction vortex over the hole location is unknown. It is possible that the lightning stroke occurred near, or even within, the tornado or suction vortex. It is also possible that the path of.the lightning stroke may have been affected by dust and debris in the tornado. 29 The following is a summation of the way the holes possibly were created. Lightning struck the ground at the hole location, cracking and loosening the soil there and causing the cracks and the overthrust to form nearby. Some dirt may have been scattered out of the hole. The tornado then passed over this area, probably containing suction vortices, whose existence is implied by the swath of trees, the windmill dragged in a loop, and the indications of suction vortices in the photo, Figure 4A. A suction vortex lifted and pushed the dirt layer,_ cracked by lightning, partially lifting the layer to form the huge crack and completely removing the dirt from the hole. Large chunks of dirt were too heavy to be rendered airborne by the suctian vortex. Thus, they were gathered and deposited in piles northeast of the holes, much like the accumulation of corn stubble into piles which constitute suction swaths. The remaining 503 of the dirt became airborne~

5. SUMMARY AND CONCLUSIONS

The survey of the Gothenburg family tornadoes has led to three basic conclusions; A. Caution should be used in assessing tornado risk based upon reports of skipping tornadoes. If the damage was really caused by a tornado family, the "skipping tornado" was not necessarily on the ground less than 1003 of the time. Similarly, meteorologists should be cautious in the use of the term "skipping" with regard to tornadoes.

B. Aerial surveys of tornadoes in rural areas can reveal much about the details of tornado structure. Such tornadoes fail to provide engineers with windspeed estimates based upon structural damage, but can often be used to study patterns of debris scatter. Examples were given.

C. Holes found within the path of the Moorefield tornado were classified as L/V holes, produced by the joint efforts of lightning and a tornado or suction vortex within the tornado. Holes in the ground can also be attributed to lightning (L holes) and lightning and wind (L/W holes). All cases known to the authors are listed in the Appendix. Other cases (both past and future) should be documented. 30

ACKNOWLEDGEMENTS

The authors are grateful to Messrs. Allen Pearson, Director, NSSFC, for alerting us to these tornadoes; Harry Spohn, MIC, North Platte NWSO, for his coopera­ tion; Tot Hohnes, Tri-City Tribtm.e, for his assistance and photos; Gene Hoppe for directing us to the suction holes; Scott Hess , for use of his photo; and to the residents who answered our questions. The authors are grateful also to Professor T. T. Fujita and Edward W. Pearl of the University of Chicago for their helpful suggestions and guidance.

This research has been performed under the U. S. Nuclear Regulatory Commission, Office of. Nuclear Regulatory Research, Contract No. E(ll-1)-2507, and renewal Contract No. AT(49-24)-0239.

REFERENCES

Brunk, I., D. Hartley, and J. Knight, 1959: Unusual Phenomena in Illinois. Weatherwise, 12, 133.

Darkow, G. L., 1971: Periodic Tornado Production by Long-Lived Parent Thunderstorms. Preprints, Seventh Conf. Severe Local Storms, Kansas City, Mo., 214-217.

Davy, E. S., 1949: Unusual Damage by a Tornado. Weather, ..!.? 156-157.

Espy, J. P., 1941: The Philosofby of Storms. Boston, Little and Brown.

Falconer, R. E., 1966: Lightning Strikes a Parked School Bus. Weather, 21, 280-281.

Finley, J. P., 1881: Report of the Tornadoes of May 29 and 30, 1879. Professional Papers of the U. S. Signal Service, No. 4, 21.

Flammarion, C. , 1905: Thunder and Lightning. London, Chatto and Windus.

Flora, S. D., 1953: Tornadoes of the United States. University of Oklahoma Press, Norman, 93.

Forbes, G. S., 1975: Relationship between Tornadoes and Hook Echoes on April 3, 1974. Preprints, Ninth Conf. Severe Local Storms, Norman, Okla. , 280-285. 31 Forbes, G. S. , 1976: Photogrammetric Characteristics of the Parker Tornado of April 3, 1974. Preprints , A Symposium ·on Tornadoes, Lubbock, T:x.

Fujita, T. T., 1963: Analytical Mesometeorology: A Review. Meteor. Monogr., ~. No. 27, 88-89.

Fujita, T. T., D. L. Bradbury, and C. F. Van Thullenar, 1970: Palm Sunday Tornadoes of April 11, 1965. Mon. Wea. Rev., 98, 40 and 47.

Fujita, T. T. and G. S. Forbes, 1974: Superoutbreak Tornadoes of April 3, 1974 as Seen in ATS Pictures. Preprints, Sixth ·Conf~ · Aerospace and Aeronautical Meteor., El Paso, 'IX., 165-172.

Fujita, T. T., 1975a: New Evidence from April 3-4, 1974 Tornadoes. Preprints, Ninth Conf. Severe -Local Storms, Norman, Okla., 248-255.

Fujita, T. T. , l 975b: Superoutbreak Tornadoes of April 3-4, 1974. Final Edition Map, The University of Chicago.

Gray, C. R., 1964: Ground Damage by Tornado. Mon. Wea. Rev., 92, 476.

Jensen, J. C., 1936: The Dodge, Nebraska, "Fireball". Science, 83, No. 2163, 574-575.

Muller-Hillebrand, D., 1963: Lightning Protection. Proc., Third Int'l. Conf. Atmos. and Space Electricity. Montreux, Switzerland. Published in Problems of Atmospheric and Space Electricity, Elsevier Puhl. Co., New York, 1965. 419.

Oliver. A. R., 1931: The Gothenburg, Nebraska Tornadoes of June 24, 1930. Mon. Wea. Rev. , 59, 228.

Storm Data, 1975: NOAA Environmental Data Service, Asheville, N. C. , 17-6, 18.

Tomlinson, C., 1860: The Thunderstorm. Londcn, Clowes and Sons.

Viemeister, P. E. , 1972: The Lightning Book. The M. I. T. Press. Cambridge, Mass. , 137 ff.

Vonnegut, B. and C. B. Moore, 1959: Giant Electrical Storms. Recent Advances in Atmospheric Electricity. Pergamon Press, 407.

Vonnegut, B., 1966: Effects of a Lightning Discharge on an Aeroplane. Weather, 21, 277-279.

Weatherwise, 1976: Unusual Weather: Ball Lightning in a February Thunderstorm Down East in Maine. Vol. 29, 84-85. (Reprinted from original newspaper accounts.) 32

APPENDIX

Partial List of Holes Created Through Lightning, Wind, or Vortex

This appendix is a partial listing of cases where lightning or tornadoes were credited with producing holes in the ground. No attempt was made to find all cases ever reported in the literature, as other cases undoubtedly went unreported. The cases are listed in chronological order, with location, date, literature reference, and description cited. A probable type has been assigned, according to the discussion in the text: L, lightning L/W, lightning and wind L/V, lightning and vortex

Probable Location Date Type Reference

Mixbury, Northamptonshire, Eng. 3 July 1725 L Tomlinson (1860} "Lightning killed a sheJiterd and five sheep in an open field. Close to the body of the man were found two holes, five inches (13 cm} in diameter, and forty inches (102 cm} deep. Near the bottom of one of the holes was a very hard stone, ten inches (25 cm} long, six inches (15 cm} broad, and four inches (lOcm} thick. The surface of the stone was vitrified." (See pages 114-115.}

Coldstream, England 19 July 1785 L Flammarion (1905} A cart laden with coal, pulled by horses, had reached the top of a hill when a loud detonation was heard. The driver and the horses were killed. "The ground was pierced with three circular holes at the very spot where the wheels had touched it when the accident happened. " (See page 46. }

Packington, England 3 Sept 1789 L Tomlinson (1860} A man was killed while standing under a tree. Lightning passed from his walking stick to the ground, producing a hole five inches (13 cm} deep and 2. 5 inches (6 cm} in diameter. Sub3equent excavation revealed that the soil was black_ened to a depth of about 10 inches (25 cm} and fused two inches (5 cm} deeper. (See page 115. }

·Boulogne, France 6 July 1822 L/V Espy (1841} A tornado of inverted cone shape was Sighted, at times throwing out "globes of fire'' from its center. A basin in the earth, 20-25 feet (7 or 8m} in circumference and 3-4 feet (about lm} deep in the middle, was found. Other tornado damage was reported. (See page 40. } 33

Appendix - 2 near Paris, France 18 June 1839 L/ V Espy (1841) A tornado was reported to have excavated the earth. There were electrical discharges and globes of fire reported with the tornado. (See page 365.)

Mt. Desert, ME 13 Feb 1853 L Weatherwise (1976) Many persons were slightly injured by vivid lightning in a freak winter snowstorm on Mt. Desert Island, coastal Maine. No buildings were damaged, but it was reported that a grove of trees was struck six times. Trees were taken out by the roots and thrown about. One tree was carried 25 feet (about 8 m). Another tree was found hanging upside-down from the top of a standing tree. The lightning swept away the snow cover and tossed stones and dirt in all directions onto the nearby snow. The lightning entered the earth to a depth of several feet in a space 8-10 feet (about 3m) in diameter and diverged in four directions. One of the paths made a chasm several feet deep, hurling chllllks of frozen earth which were up to 10 or 11 feet (about 3m) long and 4 feet (1. 2m) wide in size. The path was 370 feet (113m) long.

Lee's Summit, MO 30 May 1879 L/ V Finley (1881) "The struck the ground in a cornfield, scooping out a hole 3 feet (1 m) deep and 5-.1/2 feet (1. 7m) long. " No mention was made of lightning. The funnel was described as "very dark on the outside but lighter through its center. "

Hutchinson, KS 7 May 1927 L/V Flora (1953) "The force of the wind was terrific wherever the funnel cloud touched the ground. In Barber County holes a foot(. 3m) deep and twenty feet (6m) square were torn in the soil." No mention was made of lightning.

Gothenburg, NE 24 June 1930 L/V Oliver (1931) "Grass and shrubs were torn out by the roots, leaving the earth bare. In places even the earth was gouged out. Around this area everything was beaten down as if by a muddy torrent. " No mention was made of lightning. 34

Appendix - 3

Dodge, NE 24 June 1935 L Jensen (1936) Residents reported an intense light and an explosive noise. A hole was found in a cornfield, more than 15 feet (4. 6m) deep and 8 inches (20 cm) in diameter at the top and becoming more narrow with depth. The clay subsoil showed signs of fusion and it appeared that the clay was acted on by a high pressure. Dirt was scattered in all directions for about 3 feet(. 9m), in heaps 6 inches (15 cm) high.

Curepipe, Mauritius 24 May 1948 L/V Davy (1949) A trench was formed in the clay surface of a tennis court as a whirlwind moved northward across it. The trench ran north-south and was 60 ft (18 m) long and 1 to 2. 5 feet (. 3 - • 8 m) wide and 1 - 4 inches (2. 5 - 10 cm) deep. The clay material was all thrown westward up to 50 feet (!Sm), with pieces weighing about one pound (2.2kg) thrown 30 feet (9m). The surface material was slightly blackened and a crackling was heard for two or three minutes. One witness saw a ball of fire about two feet (. 6 m) in diameter cross the court. (Mauritius is a small island east of Madagascar at about 20 S latitude.

Fargo, ND 20 June 1957 L/ V Vonnegut and Moore (1959) Quite a few holes were found in the turf of a golf course, ranging in size from 6 to 24 inches (15- 61 cm) in diameter. One was at a .45 degree angle and more than 3 feet(. 9m) deep. At one spot the turf was rolled up into a ball for a distance of 4 feet (l.2m). Although they were in the direct path of the tornado lightning appeared to be involved because grass was seared on the sides of s~e of the holes.

Leland, IL 2 April 1959 L Brunk et al. (1959) A brilliant flash of lightning was accompanied by an explosion which broke windows and knocked over loose objects at houses nearby. In a cornfield three-quarters of a mile (1. 2km) away, a hole was found which was 7 -12 feet (2.1-3. 7m) in diameter and a foot (30cm) or more in depth. "Closer farm buildings showed no apparent damage." 35

Appendix - 4

Scandinavia (?) 1960(?) L Muller-Hillebrand (1963) Lightning struck a birch tree, passed undergr0tmd, and entered and damaged the electrical system of a house 121 feet (37m) away. The tree stood on granite covered by a thin layer of soil. The path of the current could be traced on the ground. "Several cubic meters" of earth and stones were thrown up, six windows were smashed, and about 1. 5 cubic feet ("40 or 50 liters") of earth were thrown into the upper floor of the house.

Troy, NY 9 July 1960 L Falconer (1966) Lightning struck the top of a parked school b.is and exited to the asphalt pavement through the wheel rims and tailpipe. Gullies were made in the asphalt up to 2. 5 inches (6. 3 cm) deep, 2 to 8 inches (5 - 20 cm) wide, and up to 10 feet (3 m) long. Several pieces of asphalt landed on top of the bus.

Marion, MS 5 April 1964 L/W Gray (1964) The sod was pulled out down to the clay depth, about 8 inches (20 cm). The sod was ripped open in an area 20 feet (6 m) wide and 50 feet (15 m) long. Huge chunks of soil were thrown in all directions around the hole for a distance Of about 100 feet (30m). Fifty feet (15m) to the southwest, huge semicircular cracks were forced open in the sod in an area about 10 feet (3 m) in diameter. No mention was made of lightning.

Greentown, IN 11 April 1965 L/V Fujita et al. (1970) The tornado was reported to have dug the lawn out from many backyards. Nearby, near Alto, the sod was reportedly rolled up. No mention was made of lightning.

Salt Lake City, UT 15 Oct 1965 L/W (?) Vonnegut (1966) An aircraft was struck by lightning as it was taking off. The current passed from the wheel rims to the runway, causing three holes in the asphalt. The largest was 5 feet (1. 5 m) in diameter and 6 to 8 inches (15 - 20 cm) deep. Pieces of asphalt as large as a football were hurled 100 to 150 feet (30 - 46m) down the runway. There were burns on the wheel rims. Flying asphalt made holes in the fuselage. 36

Appendix - 5

3 Joliet, IL 6 April 1972 L/V Pearl (1976) A hole was found midway between a house and a garage, roughly 24 feet (7. 3m) apart. The garage was destroyed by the tornado and people in the house witnessed a bright flash. The hole was cone shaped, roughly 3 feet (. 9m) deep and 3 feet(. 9m) in diameter at the top, with smooth walls and bottom. None of the evacuated dirt could be found nearby.

Moorefield, NE 18 June 1975 L/V This }»per A hole about 10 feet (3m) by 6. 5 feet (2m) and up to 18. 5 inches (47 cm) deep was found in the direct path of a tomado. Chunks of dirt were scattered up to 36 feet (11 m) to the north and northeast of the hole• . Nearby was a huge crack, about 10 feet (3m) long and a foot (30 cm) wide and up to about 11 inches (29 cm) deep. There was also an area where the layer of di.rt slid over top of the other, like a thrust fault. Roughly 503 of the dirt removed from the hole was not accounted for in the piles of di.rt scattered beyond the hole. There was no sign of scorching of dirt or grass in the vicinity.

3Pearl, E. W., 1976: Personal communication. MESOMETEOROLOGY PROJECT --- RESEARCH PAPERS (Continued from front cover) 42. • A Study of Factors Contributing to Dissipation of Energy in a Developing Cumulonimbus - Rodger A. Brown and Tetsuya Fujita 43. A Program for Com put er Gridding of Satellite PhotograJXis for Mesoscale Research - William D. Bonner 44. Comparison of Grassland Surface Temperatures Measured by TIROS VII and Airborne Radiometers Wider Clear Sky and Cirriform Cloud Conditions - Ronald M. Reap 45. Death Valley Temperature Analysis Utilizing Nimbus I Infrared Data and Ground-Based Measurements - Ronald M. Reap and Tetsuya Fujita 46. On the "ThWlderstorm-High Controversy" - Rodger A. Brown 4 7. Application of Precise Fujita Method on Nimbus I Photo Gridding - Lt. Cmd, Ruben Nasta 48. A Proposed Method of Estimating Cloud-top Temperature, Cloud Cover, and Emissivity and Whiteness of Clouds from Short- and Long- wave Radiation Data Obtained by TIROS Scanning Radiometers - T. Fujita and H. Grandoso 49. Aerial Survey of the Palm Sunday Tornadoes of April 11, 1965 - Tetsuya Fujita 50, Early Stage of Tornado Development as Revealed by Satellite Photographs - Tetsuya Fujita 51. Features and Motions of Radar Echoes on Palm Sunday, 1965 - D. L. Bradbury and T. Fujita 52. Stability and Differential Advection Associated with Tornado Development - Tetsuya Fujita and Dorothy L. Bradbury 53. Estimated Wind Speed6 of the Palm Sunday Tornadoes - Tetsuya Fujita 54. On the Determination of Exchange Coefficients: Part II - Rotating and Nonrotating Convective Qirrents - Rodger A. Brown 55. Satellite Meteorological Study of Evaporation and Cloud Formation over the Western Pacific under the Influence of the Winter Monsoon - K. Tsuchiya and T. Fujita · 56, A Proposed Mechanism of Snowstorm Mesojet over Japan under the Influence of the Winter Monsoon - T. Fujita anl! K. Tsuchiya 57. Some Effects of Lake Michigan upon Squall Lines and Summertime Convection - Walter A. Lyons 58. Angular Dependence of Reflection from Stratiform Clouds as Measured by TIROS IV Scanning Radiometers - A. Rabbe 59. Use of Wet-beam Doppler Winds in the Determination of the Vertical Velocity of Raindrops inside Hurricane Rainbands - T. Fujita, P. Black and A. Loesch 60. A Model of TyJXioons Accompanied by Inner and Outer Ra.inbands - Tetsuya Fujita, Tatsuo lzawa., Kazuo Watanabe and !chiro Imai 61. Three-Dimensional Growth Characteristics of an Orographic Thtmderstorm System - Rodger A. Brown 62. Split of a Thunderstorm into Anticyclonic and Cyclonic Storms and their Motion as Determined from Numerical Model Experiments - Tetsuya Fujita and Hector Grandoso 63. Preliminary Investigation of Peri pheral Subsidence Associated with Hurricane Outflow - Ronald M. Reap 64. The T1me Change of Cloud Features in Hurricane Anna, 1961, from the Easterly Wave Stage to Hurricane Dissipation - James E. Arnold 65. Easterly Wave Activity over Africa and in the Atlantic with a Note on the lntertropical Convergence Zone during Early July 1961 - James E. Arnold 66, Mesoscale Motions in Oceanic Stratus as Revealed by Satellite Data - Walter A. Lyons and Tetsuya Fujita 67. Mesoscale Aspects of Orographic Influences on F low and Precipitation Patterns - Tetsuya Fujita 68. A Mesometeorological Study of a Subtropical -Hidetoshi Arakawa, Kazuo Watanabe, Kiyoshi Tsuchiya and Tetsuya Fujita 69. Estimation of Tornado Wind Speed from Characteristic Ground Marks - Tets uya Fujita, Dorothy L. Bradbury and Peter G. Black 70. Computation of Height and Velocity of Clouds from Dual, Whole-Sky, Time-Lapse Picture Sequences - Dorothy L. Bradbury and Tetsuya Fujita 71. A Study of Mesoscale Cloud Motions Computed from A TS-I and Terrestrial Photographs - Tetsuya Fujita, Dorothy L. Bradbury, Clifford Murino and Louis Hull 72. Aerial Measurement of Radiation Temperatures over Mt. Fuji and Tokyo Areas and Their Application to the Determination of Ground­ and Water-Surface Temperatures - Tetsuya Fujita, Gisela Baralt and Kiyoshi Tsuchiya 73. Angular Dependence of Reflected Solar Radiation from Sahara Measured by TIROS VII in a Torquing Maneuver - Rene Mendez. 74. The Control of Summertime Cumuli and Thunderstorms by Lake Michigan During Non-Lake Breeze Conditions - Walter A. Lyons and John W. Wilson 75. Heavy Snow in the Ghicago Area as Revealed by Satellite Pictures - James Bunting and Donna Lamb 76. A Model of TyJXioons with Outflow and Subsidence Layers - Tatsuo lzawa

n. Yaw Corrections for Accurate Griddlng of Nimbus HR!R Data - R. A. Madden 78. Formation and Structure of Equatorial Anticyclones caused by Large-Scale Cross Equatorial Plows determined by ATS I Photographs - T. T. Fujita, K. Watanabe and T. lzawa 79. Determination of Mass 0..tflow fr

87. Patterns o( Equiva lent Blackbody Temperature and Reflectance of Model Clouda computed by changing Radiometer's Field of View -J. ). Tecs on 88. Lubbock Tornadoes of 11 May 1970 - T. T. Fujita

~9 . Estimate of Ar eal Probability of Tornadoes Crom In!latlonary Reporting of their Frequencies • T. T. Fujita 90. Application or ATS lII Photographs for determination or Dust and Cloud Velocities over Northern Tropical Atlantic - T. T. Fujita

91 . A Proposed Olaracterizatlon of Tornadoes and Hurricanes by Area ~nd Intensity • T. T . Fujita 92. Estimate or Maxlmwn Wind Speeda of Tornadoes In Thrtt Northwestern States • T . T. Fujita 93. In- and Outflow Field or Hurricane Debbie as revealed by Echo and Cloud Velocities from ·Airborne Radar and ATS·W Pictures· T . T . Fujita and P. G. Black (Reprinted from Preprint or Radar Conference, Nov. 17-20, 1970, Tucson, Arizona) 94. O>aracterlzatlon of 1965 Tornadoes by thei r Area and Intensity - J. J. Tecsot1 '95. Computation or Height and Velocity of Clouda over Barbados from a Whole-!i:y camera Network • R. D. Lyom 96. The Filling over Land of Hurricane Camtlle, August 17- 18, 1969 - D. L. Bradbury 97. Tornado Occurrences related to Overshooting Cloud- Top Heights aa detennlned from ATS Pictures - T. T. Fujita 98. F pp Tornado Scale and Its Applications - T. T. Fujita and A. D. Pearson 99. Preliminary Res ults of Tornado Watch Experiment 1971 • T. T . Fujlts, J. }. Tecson and L. A. Schaal 100. F·Scale Class ification or 1971 Tornadoes • T. T. Fujita 101 . Typhoon-Associated Tornadoes In Japan and new evidence of SUctlcm Vortices In a Tornado near Tokyo - T. T. Fujita 102. Proposed Mechanism of SUction Spots accompanied by Tornadoes - T. T. Fujita 103. A Climatological Study or Cloud Formation o•er the Atlantic during Winter Monaoon • H. Sbltara ••1cu. Statistical Analys is of 1971 Tomadoes - E. w. Pearl 105. Estimate al. Maximum Wlndspeeds or Tornadoes In Southernmost Rockies - T. T. Fujita 106. Uee of ATS Pictures In Hurricane-Modification • T. T. Fujita 107. Mesoecale Analysis of Tropical Latin America - T. T. Fujita

108. Tornadoes Around Tbe World - T. T. Fujita (Reprinted from Weatherwlse, ~ No. 2, April 1973) 109. A Study or Satellite-Observed Cloud Patterns of Tropical Cyclcmes • E. E. Balogun 110. METRACCM System of Cloud-Velocity detennlnation from Geostationary Satellite l'lctures - Y. M. Olang, J. J. Tecson and T, T . Fujita 111 . Proposed Mechanism of Tornado Formation from Rotating Thunderstorm - T. T. Fujita 112. Joliet Tornado of April 6, 1972 - E. W. Pearl 113. Results of F PP Claasiflcstion of 1971and1972 Tornadoes - T . T . Fujita and A. D. Pearson 114, Satellite-Tracked Cumulus Velocities - T. T, Fujlta, E. W. Pearl and W. E. Shenk

115. General and Local Circulatlcm of Manti~ and Aanospbere toward Prediction of Ba.nbqual

120, Jumbo Tornado Outbreak of 3 April 1974 - T. T. Fujita 121, Cloud Velocities Over Tbe North Atlantic Computed From ATS Picture Sequences · Y. M. Oiang ed J. J. Tecson 122. Analysis of Anvil Growth for ATS Pictures - Y. M. Olang

••123. Evaluation ct. Tornado Risk Baaed OD F -Scale Distribution -E. W. Pearl 124. Superoutbrealc Tornadoes Of April 3, 1974 AIJ Seen In ATS Pictures - T. T. Fujita and G. S, Forbes 125. Kinematic Analysla of Tropical Storm Baaed On ATS Cloud Motions - J. J. Tecson and T. T. Fujita 126. Overshooting Top Behavior of Three Tornado-Pr<>Alclng Thunderstorms - T . A. Umenbofer 127. New Evidence from April 3·4, 1974 Tornadoes - T. T. Fujita 128. Long-Term Fluctuation of Tornado Activities - T . T. Fujita, A. Pearson and D. M. Ludlum 129. Relationship betwttn Tornadoes and Hook Echoes on April 3. 1974 - G. S. Forbes 130. Cloud-Top Plrameters - A Hall Indicator - E. W. Pearl, W. E. Sbenlc and W. Skillman 131. Detection of Severe Storms by Satellttea - T . T. Fujita