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Tornado Oddities

Of all the strange oddities, a few are not readily explainable and among these is the ubiquitous plucked chicken.

Within the damage descriptions of rural tornadoes, there will likely be mention of a chicken "stripped clean of every feather."

It has been suggested that the feathers explode off the bird in the tornado's low pressure.

That explanation does not hold up because the bird would be blown away long before experiencing the lowest pressure at the center of the tornado.

Secondly, the lowest pressure in a tornado is probably not low enough to explode a feather .... if indeed a feather would ever explode.

It is curious how the exploding feather theory became accepted by so many people over the years, even though the remains of an exploded feather was never found.

Tornadoes & Chickens?

But when it come to tornadoes, facts, evidence and accurate descriptions have never bothered amateur tornado theoreticians and much of the news media.

In 1842, Elias Loomis performed an experiment that left much to be desired in the control of experimental variables.

It received wide attention at the time. His goal was to gain insight into the wind speed needed to defeather a chicken.

An account written a few years later states: "In order to determine the velocity needed to strip feathers, the six-pounder (cannon) was loaded with five ounces of powder, and for a ball a chicken was killed.

The gun was pointed upwards and fired. The feathers rose twenty or thirty feet and were scattered by the wind.

On examination, they were found to be pulled out clean, the skin seldom adhering to them.

The body was torn into small fragments, only a part of which could be found.

The velocity was 341 miles per hour." Loomis speculated that if a live bird was fired at 100 miles per hour, the results would be more successful, but, to my knowledge he never attempted it.

He did place dead chickens under a vacuum jar to see if the feathers would explode. They did not.

A widely accepted alternative theory in the 19th century was that opposing electric charges during the tornado's passage stripped feathers from chickens and tore the clothes from people.

It was supposed that the highly charged tornado induced an opposite charge in objects as it approached and things would be sent flying.

While static electricity is undoubtedly present in a debris filled funnel, this makes no scientific sense whatever.

There is simply no mechanism that would produce powerful opposing charges on the bird and on the feather at the same time.

The most likely explanation (Vonnegut, 1965) for the defeathering of a chicken is the protective response called "flight molt."

Chickens are not stripped clean, but in actuality they lose a large percentage of their feathers under stress in this flight molt process.

In a predator-chicken chase situation, flight molt would give the predator a mouth full of feathers instead of fresh fowl.

In a tornado, the panicked chicken's feathers simply become loose and are blown off.

Stories of chickens found dead, sitting at attention and stripped clean of feathers may be on par with reports of the blowing of a cow's horn or a two-gallon jug being blown into a quart bottle without cracking.

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FALLOUT OF DEBRIS FROM TORNADIC THUNDERSTORMS:
An Historical Perspective And Two Examples From VORTEX
ABSTRACT

We report preliminary results of an investigation of debris lofted by tornadoes, its long- distance transport by thunderstorms, and its subsequent fallout.

We begin with a review of historical accounts, including the unique study of the1984 Barneveld, Wisconsin tornado by Anderson.

Our review shows that long-distance transport and fallout of debris have occurred and that distances involved have been significant.

We then report first-hand evidence of these phenomena in two events with F2 tornadoes: the Tuskahoma, Oklahoma tornado of 25 April 1994 and the Gainesville, Texas tornadoes of 26 April 1994.

In both cases, traceable material in the form of canceled checks, bills-of-sale, invoices, and legal documents were reported to us.

We were able to locate the source locations for several of these items.

We close with some conjectures on the implications of these first findings

1. INTRODUCTION

Several times each year tornadoes strike communities in the United States, damaging homes, businesses, and other structures.

Great efforts have been made to understand how tornadic winds damage structures.

Less attention has been given to other, closely related phenomena.

While there have been a few efforts to investigate low altitude lofting and deposition of material by tornadic windfields (usually motivated by an interest in missile hazards), the lofting of debris to great heights, its long-distance transport, and its fallout far downstream from its source have received little attention.

Indeed, most of our knowledge of such phenomena is anecdotal -- a newspaper clipping is typical.

These phenomena pose interesting scientific questions and challenges, and are the subject of this paper

1.1 The Barneveld, Wisconsin Tornado

Motivation for this study was provided by Anderson's (1985a) investigation of debris lofting, long-distance transport, and fallout that accompanied the 7/8 June 1984 outbreak of tornadoes in southern Wisconsin.

Seven tornadoes were produced in southern Wisconsin by a complex of thunderstorms.

One of these, a violent tornado (rated F5 on the Fujita Intensity Scale; Fujita, 1971, 1973), destroyed approximately 90% of the small village of Barneveld.

A large amount of debris from this village was lofted, transported, and deposited in a wide swath running from southwest to northeast across Wisconsin.

In the days following the outbreak, Anderson and his students conducted a ground survey and a mail and telephone campaign to obtain data on the fallout of debris.

Anderson classified fallout from this storm as follows:

PAPER

This consisted of many different types of paper items -- most important were checks, letters, bills, and invoices.

(Such items can be called "traceable paper", since they contain addresses that allow the source to be identified.)

Anderson Reports:

"Paper debris was found throughout the contiguous area with a wider extent than the light debris.

Paper debris was found in widely scattered locations north of the contiguous area reaching the town of Bonduel, some 20 miles northwest of the city of Green Bay.

The maximum width of this scattered paper was 23 miles at 110 miles downstream of Barneveld."

LIGHT (1 pound)

This consisted of tarpaper, shingles, soffit, insulation bits, etc... from buildings, bank pouches, and occasionally bundles of light materials such as canceled bank checks and statements in envelopes.

In the BarnevelD Storm

"A bank pouch lettered 'Barneveld State Bank' was found in Mayville, 86 miles ENE of Barneveld."

(This pouch is also notable since it was the one item of light material found outside the contiguous debris area.)

"The lighter materials are not deposited symmetrically around the heavy debris path but lie more to the east, making the heavy debris path lie nearer the western edge of the contiguous deposit area."

HEAVY (1 pound)

This consists of pieces of plywood, aluminum siding, boards, etc... from buildings.

Anderson states "..., the heavy material lies along a narrow path from Barneveld to east of Redgranite, about 85 miles in length.

The path of the heavy material shows branching at three places along its length, and it is partially interrupted in the Portage region."

1.2 Objectives

While showing conclusively that lofting, debris transport, and fallout occur, Anderson's study is the only one of its type in modern times (see Peterson, 1993, for discussion of three early European studies; these are mentioned briefly below).

It does not provide a sufficient basis from which to judge either how often these phenomena occur or what happens in tornadoes of lesser intensity.

We would like to be able to answer questions such as

How common is the high altitude lofting, long-distance transport, and subsequent fallout of debris such as occurred following the Barneveld tornado?

Is long-distance transport a phenomenon associated only with thunderstorms that produce the most intense tornadoes?

What is the maximum distance debris is likely to be transported?

How is the distribution of fallout related to storm structure?

As an application, we would like to be able to assess the risk posed by lofting, long- distance transport, and fallout of hazardous material (e.g., toxic chemical or radioactive material, medical waste in bulk storage, or even contaminated soil from a Superfund site) from tornadic thunderstorms.

If lofting of material high into a thunderstorm, followed by its transport and fallout downstream, is a common event, then tornadoes pose serious hazards well beyond the direct impact of their high winds.

In an attempt to answer such questions, we recently began a three-year effort to gather data on lofting, transport, and fallout from tornadic thunderstorms.

The objective of this study is to collect several data sets containing detailed information on these phenomena and on the thunderstorms causing them.

For this reason, while we seek reports of fallout occurring anywhere in the U.S. during all seasons of the year, we are focusing our efforts on storms occurring in the VORTEX region during the intensive observing periods of that program

Here we report on some preliminary work and our first year's efforts.

Specifically, in Section 2 we discuss evidence gleaned from a survey of historical records.

In Section 3 we present evidence from two events with F2 tornadoes that occurred in the spring of 1994.

2. HISTORICAL EVIDENCE

A review of accounts of tornadoes -- by no means exhaustive -- finds a number of reports of debris being transported long distances.

While many of these accounts -- especially those prior to 1950 or so -- are highly subjective and likely exaggerated, when taken together, they provide useful insights on lofting, transport, and fallout.

In Grazulis (1993) [1], for the period 1871 through 1990, 86 out of 12,651 tornado accounts provided 121 reports of debris found more than five miles downstream, while a review of other publications on significant tornadic events which occurred in this same 120-year period provided an additional 42 reports.

A tabulation of these 163 reports, giving dates, locations, F-scales and transport distances, is given in Table A1 of the Appendix [2].

(It is interesting to speculate why lofting, transport, and fallout have not attracted more scientific scrutiny.

Possibly it reflects scientists' dislike of working with anecdotal and circumstantial data provided by laypersons, the type of data central to an initial investigation of these phenomena.

Further, this complex chain of events -- lofting, long-distance transport, fallout -- occurring in the rapidly varying environment in and around a thunderstorm has probably been impractical to explore outside a focused field program such as VORTEX.)

Items reported to have been transported by tornadic thunderstorms range from paper products, such as canceled checks and photographs, to large, heavy objects, such as an airplane wing and a carton of deer hides [3].

In an account of the Tri-State tornado of 18 March 1925, Felknor (1992, pp. 73-74) cites the Murphysboro Daily Independent: "... a bond for a deed was blown to Lawrenceville [Illinois], 125 miles away."

In a detailed discussion of the 9 June 1953 tornado in Worchester, Massachusetts, O'Toole (1993, p. 255), reports "Emily McNutt of South Weymouth found a wedding gown in her backyard.

It was dirty, as would have been expected, but was intact and in surprisingly good condition.

A label sewn into the gown read 'McDonald, Worchester', indicating that the gown had been blown some fifty miles to its final landing place."

As another example typical of many reports, in a discussion of the Jordan, Iowa tornadoes of 12/13 June 1976 , Stanford (1987, pp. 95-97) reports

"Several days after the tornadoes, a photograph was returned to Jordan by a couple who had found it in their cornfield near Ackley, Iowa, more than 50 miles northeast of Jordan.

The couple wondered if the photograph, about 16 by 20 inches, had possibly come from Jordan.

Neighbors recognized the children shown in the photograph and it was returned to its owners, a family whose home had been destroyed in Jordan.

Prior to the storm, the photograph had been hanging on a wall in their home."

Year By Year Distribution

The year-by-year distribution of the 93 tornado events which yielded the 163 reports in Table A1 is plotted in Figure 3.

This distribution shows that although tornadoes with reports of long-distance transport occur with regular frequency, more than half (50 events, 90 reports) occurred in the fifty years prior to 1920.

In the period 1871 through 1990, the number of tornadoes reported annually has increased from less than 100 in the period 1871-1916 (Fujita, 1987, p. 36) to greater than 1100 in 1990.

Therefore, the number of tornado events with reports of long-distance debris transport, per year, as a fraction of the total number of recorded tornadoes for that year, has decreased in recent years.

We conjecture that this is due in part to a shift (beginning in the early 1950's and with increased emphasis since the mid-1970's) by the operational and research communities from detailed analyses of each year's relatively few significant events, to a risk-assessment approach that is focused on characterizing the intensities for all tornadoes that occur in a given year.

In using the current F-scale for this characterization, only damage in the path of a tornado need be assessed to ascertain intensity.

Entries in Storm Data, the official government publication containing these characterizations, tend to be short and limited to items that substantiate estimates of intensity.

Further, this broader approach to documenting tornadoes has increased most notably the number of weak (F0 and F1) tornadoes reported each year, events for which debris lofting and long-distance transport seem less likely.

Debris Reports

Figure 4 shows the number distribution of the 163 debris reports as a function of debris type and distance transported.

Using the definitions discussed in Section 1.1, the transported items were categorized as "paper", "light", or "heavy".

If the account of an event was unclear as to the size or weight of the debris, the item was classified as having "unknown" weight; such accounts typically included phrases like "pieces of..." or "...buildings were destroyed.

Debris was carried ... miles away."

(While it would be desirable to also characterize transported objects in terms of their aerodynamic shapes, this proved impractical due to the lack of information in most historical accounts.

An important exception is "paper", especially personal bank checks, since such items are very often of standard size.)

The overall shape of the distribution in Figure 4 is roughly what one would anticipate.

Most items fall out fairly close to their points of origin.

Heavy items tend to come down closest to their source locations, followed by light items.

Paper items, the lightest materials, are carried the farthest downstream as indicated by the long tail of the distribution.

The secondary peak in the distribution which occurs at a distance of 85-90 miles (135-145 kilometers) in Figure 4 (and also in Figure 5) is due to multiple reports of debris found at the same location, all associated with the F4 Great Bend, Kansas tornado of 10 November 1915.

Figure 4 suggests that most heavy debris falls out within 50 miles (80 kilometers) of its source, while most light debris falls out within 90 miles (145 kilometers) from its source.

Paper debris, on the other hand, can be deposited much farther.

The farthest reported distance for any fallout is 210 miles (335 kilometers); this was a canceled check, found in Palmyra, Nebraska, transported by the thunderstorm that produced the 1915 Great Bend, Kansas tornado.

This tornadic thunderstorm also transported light and heavy objects farther than any other storm on record.

Clothing, shingles, and fragments of books were found in Glasco, 87 miles (140 kilometers) to the northeast of Great Bend.

A sack of flour, categorized as heavy, was found about 110 miles (175 kilometers) to the northeast. (Grazulis, 1993, personal communication, noted this to be "perhaps the longest distance ever recorded for an object weighing more than one pound.")

This particular report may be anomalous, since the second-farthest report of transport of a "heavy" item is only 50 miles (80 kilometers).

Table One

Table 1.

The distribution of 163 reports of paper, light, heavy or unknown weight debris as a function of tornado F-scale for the 120-year period 1871-1990.

The number of tornadoes with debris reports for each F-scale value is listed in parentheses in the first column.

Total number of tornado events with debris reports for the period is 93.

Table 1 displays the 163 debris reports as a function of F-scale.

These and subsequent statistics using the F-scale must be interpreted with caution, especially if inferences are to be made about tornado dynamics and wind speeds, as the Fujita Intensity Scale is really a tornado damage rating scale -- see Doswell and Burgess (1988) for a discussion of this point.

(Recall that the F-scale value assigned to an event characterizes the most severe damage observed; typically this will have occurred over only a small portion of the tornado's track.)

While there is some correlation between damage rating and tornado strength, the correlation is not a perfect one.

Further uncertainties enter in the assignment of F-scale values from anecdotal information.

The net effect is that the F-scale value assigned to many events probably contains an uncertainty approaching +/- 1; there also appears to be a tendency to err on the high side in many events.

In Table 1, there are no data on fallout linked to F0 or F1 tornadoes since Grazulis focused on strong (F2 and F3) and violent (F4 and F5) tornadoes.

The largest number of reports of long-distance debris transport (about 75% of the total) are associated with violent tornadoes, particularly those rated F4 in intensity.

While the number of reports associated with F5 tornadoes appears small, this is a result of the fact that damage of this intensity is very rare (on the order of 0.1% of all tornadoes, based on tornado accounts 1953 through 1990).

Similarly, F4 events are also a small fraction of all tornadoes (on the order of 1%).

Hence, that 57 violent events appear here suggests that a relatively high percentage of violent tornadoes (roughly 4%) leads to long-distance debris fallout.

In contrast, while there are some reports of long-distance debris transport by strong tornadoes, the number here is a relatively small percentage of all such events (roughly 0.4%).

Since strong events account for roughly 28% of all tornadoes, this suggests debris transport by thunderstorms producing such events is rare.

Figure 5

Plot of number of debris reports as a function of F-scale and distance for the 120-year period 1871-1990.

Overall distribution is the same as in Figure 4, but each bar is now differently proportioned.

Figure 5 shows the same number distribution as Figure 4, but with the bars now showing dependence on F-scale.

The items which traveled the farthest distances, 205 and 210 miles, were both transported by thunderstorms producing F4 tornadoes.

The greatest distance traveled by debris associated with an F2 tornado was 130 miles by a piece of copper plate from the 20 March 1888 tornado in Calhoun, Georgia (Grazulis, 1993).

Figure 6. Composite pattern of 68 debris reports associated with 31 tornadic storms, 1871-1990.

The arrow indicates "storm direction", and has arbitrarily been oriented SW to NE.

Debris items are plotted by azimuth and distance from their source.

Sixty-eight debris reports from 31 of the 93 tornado events represented in Table A1 -- ones in which the descriptions of the fallout were particularly detailed -- were combined to produce Figure 6, a composite plot of fallout locations with respect to estimated storm motion.

Cases used in the plot were those in which the debris report was linked to a town name, or in which a direction and distance from the debris source was given.

For example, on 25 April 1957 in southeastern Nebraska, Grazulis (1993, p. 1005) reports that an F4 tornado

"...moved ENE for 2 m N of Geneva, passing 1 m N of Friend, hitting the west half of Milford and ending 2 m N of Pleasant Dale...Milford debris was carried 40 miles to the NE, falling at Wahoo."

Locations of fallout finds and source points were given in 48 reports. In the other 20 reports, a direction and distance from the source were provided.

(Although there were actually 83 usable reports, only 68 are plotted in Figure 6; the other 15 overlap, i.e., same event, same type, same fallout location.)

Using latitude and longitude coordinates of the noted towns or other locations, an azimuth and distance from the source was computed for each fallout site.

The direction of storm movement for each event was estimated very roughly (to within +/- 10 °, say) as the direction of the line tangent to the beginning portion of the tornado track; here this will be referred to as "storm direction".

The tracks were then rotated to align along a common direction (here drawn aesthetically as 225 °, or from southwest to northeast) and relative debris locations plotted accordingly.

Because of the limited number of reports, no effort was made to stratify these data by tornado intensity.

Figure 6 shows that, of the 68 debris items plotted, 53 items (78%) fell to the left [4] of the composite "storm direction".

Of the 15 items which fell to the right, only two items (one "paper" and one "light") fell beyond -10 °.

Therefore, 66 items of debris (97% of the reports) fell either approximately along (i.e., within 10 ° to the right or left) or to the left of "storm direction".

Relative to the "storm direction", the composite debris pattern shown in Figure 6 suggests the most concentrated area of debris is between 10 ° and 35 °, that is, to the left of the composite "storm direction"; fifty-four percent of the points fall in this area.

Thirty-two percent fall along the "storm direction".

Paper was scattered the farthest, for distances as great as 210 miles, between angles of -40 ° and 70 °.

Light debris was found up to 87 miles downstream, between angles of -38 ° and 75 °.

Heavy items, with the exception of the flour sack, were carried up to 50 miles, between angles of -10 ° and 75 °.

Items of unknown weight were carried up to 130 miles, between angles of -5 ° and 80 ° with respect to "storm direction".

This pattern of long-distance debris transport and fallout has similarities to that found by Anderson for the Barneveld tornado.

In constructing a fallout map, Anderson found that the "...contiguous area of debris [lay] mainly to the west and north of the Barneveld-Arlington-Markesan tornado path.", that is, most of the fallout was to the left of the storm's track.

Similarly, Peterson (1993) has described three European events in which the debris was to the left of the tornado track.

These events include the St. Claude, France tornado of 1890; the Woldegk, Germany tornado on 29 June 1764; and the 24 July 1930 tornado in the Treviso-Udine district of Italy.

3. TWO RECENT EXAMPLES & 3.1 VORTEX

The Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) is a project being conducted by the NOAA National Severe Storms Laboratory in partnership with researchers from numerous universities and other federal agencies.

Its goal is to gain better understanding of how tornadoes form, the role of the environment in producing tornadic storms, the structure of tornadoes, and how tornadoes produce their incredible damage.

In a study area covering the southern half of Kansas, most of Oklahoma, and parts of the Texas panhandle and northern Texas, project participants are investigating target storms using portable and airborne Doppler radars; vehicular-mounted weather stations; movie, video, and still photography teams; and mobile facilities for launching weather balloons.

This "mobile laboratory" supplements and complements the array of fixed WSR-88D radars, ASOS and conventional observing stations, and Oklahoma Mesonetwork stations in the study area.

The first intensive observing period for VORTEX was 1 April through 15 June1994; the second intensive observing period is planned for the same ten weeks in 1995.

3.2 The Tornado Debris Research Project

The Tornado Debris Research Project, administered from the School of Meteorology at the University of Oklahoma, aims to study debris transported long distances by tornadic thunderstorms, especially those which occur within the VORTEX study area.

The goal of the project is to locate "traceable debris" and infer a trajectory for the debris based on the dynamics of the transporting storm and the structure of the wind field in the mesoscale environment.

In order to locate debris, assistance from the public is essential.

Prior to the start of a VORTEX intensive observing period, contact letters are sent to law enforcement, emergency management, and news media personnel in the study area and also "downwind" in Kansas, Missouri and Arkansas.

These contact letters acquaint these individuals with the project, and indicate what will happen when a tornado strikes.

When a tornado is reported to have caused significant damage within the study area, a press release is sent by facsimile to news media and emergency management personnel in counties downstream from where the tornado struck.

The press release asks the public to be on the lookout for debris which may have been transported by the tornado.

Debris reports are directed to the Tornado Debris Research Project via the Tornado Debris Hotline (1-800-3DEBRIS), by electronic mail to debris@metgem.gcn.ou.edu, or by regular mail.

Persons who discover debris are asked to note what the item is, the specific location where it was found, the time it was found, and if there are any identifying marks or writing that might indicate its origin.

Most debris items are then sent to the Tornado Debris Research Project for further study and an attempt to return the items to their owners.

Through this procedure we have identified small amounts of fallout associated with two tornadoes that occurred in the VORTEX study area in April 1994.

3.3 The Tuskahoma/Talihina, Oklahoma Tornado Of 25 April 1994

At approximately 6:45 p.m. on 25 April 1994, a tornado of unknown intensity touched down in southeastern Oklahoma, just north of Tuskahoma.

Reports obtained from the Tulsa, Oklahoma and Fort Smith, Arkansas offices of the National Weather Service suggest that this tornado was the first in a sequence of brief touchdowns and short damage tracks along a 20-mile (30-kilometer) long path running to the northeast, passing through and finally ending to the northeast of Talihina, Oklahoma.

In Talihina, F2 damage was reported.

Radar imagery showed that the storm which produced this sequence of tornadoes subsequently moved to the northeast over Sebastian, Crawford, Logan, Franklin, Johnson and Newton counties in Arkansas.

After receiving a post-storm survey report from the Meteorologist-in-Charge at the Fort Smith, Arkansas National Weather Service office, press releases were sent to newspapers in Poteau, Oklahoma and Clarksville, Fayetteville, Fort Smith, Greenwood, Huntsville, Springdale and Van Buren, Arkansas in order to alert the public to watch for debris that may have been transported by the tornado.

Two residents of Fort Smith, Arkansas and a third from Alma, Arkansas, a suburban community about 10 miles (15 kilometers) to the northeast of Fort Smith, responded to the press releases, reporting that they had found canceled checks and a receipt which were likely transported by the thunderstorm.

The items were from a defunct gas company formerly located in Clayton, Oklahoma.

Subsequent interviews with the former owners of the gas company revealed that the items had been in a storage shed which was demolished by this storm.

The shed was near Tuskahoma, nearly 70 miles (115 kilometers) from Fort Smith and 80 miles (130 kilometers) from Alma.

3.4 The Gainesville, Texas Tornadoes of 26 April 1994

At approximately 3:20 p.m. on 26 April 1994 two tornadoes hit Gainesville, Texas, causing extensive damage to homes and property in Gainesville and rural Cooke County.

The first tornado, rated F2, touched down on the west side of town and tracked six to eight miles east-northeast.

The second tornado, also rated F2, touched down three minutes after and about one-half to three-quarter miles south of the first, and moved east-northeast, remaining on the ground for three to four miles.

This second tornado was reported to have been rotating anti-cyclonically.

Radar showed that the storm which produced the tornadoes moved to the northeast over Love, Marshall, Bryan, Johnston, and Atoka counties in Oklahoma.

News releases informing the public of possible debris fallout from this storm were sent to newspapers in Gainesville, Texas; and Ardmore, Durant, Konawa, Madill, Seminole, Tishomingo, Wetumka, and Wewoka, Oklahoma.

Six telephone calls or letters reporting debris finds were received in response to the news releases.

For four of the six reports, the source of the debris was determined.

These four debris items, which landed at three separate locations, were all traced to a ranch site about four miles north-northeast of downtown Gainesville.

A canceled check and a page from a bank statement were both found on property four miles northeast of the source location.

A title deed from the sale of property was found near Lake Texoma in Bryan County, Oklahoma, a distance of nearly 40 miles (65 kilometers) from the source.

A second canceled check was found in Caddo, Oklahoma, nearly 60 miles (95 kilometers) from the source.

In addition, three photographs were retrieved from a pasture approximately two miles north of the Gainesville city limit.

The source of the photographs has not been determined.

Part of another canceled check of unknown origin was also found in Gainesville.

Further, siding and other building materials of unknown origin were found approximately one mile (1.2 kilometer) west of Gainesville; all nearby buildings were undamaged by the storm.

4. CLOSING CONJECTURES

It is premature to draw general conclusions about these phenomena.

However, the historical record and our experiences in the spring of 1994 suggest the following points:

Debris, sometimes large pieces, does fall from some tornadic storms well downstream from its source.

While most lofted material falls out locally, we suspect a small amount of debris is carried upward in or around the tornado core and transferred into the circulation of the mesocyclone.

The rising air in the mesocyclone apparently carries the material still higher into the parent storm.

Exactly how high material is lofted and how the transfer occurs remains unclear.

Consistent with Anderson's findings, composited historical data contains hints that there is organization in how fallout occurs downstream.

The large majority of historical accounts of long-distance transport of debris place the fallout to the left of the direction of storm movement.

There is also a suggestion of a concentrated band of material within the overall fallout pattern.

Possibly this tendency for fallout to be concentrated to the left of storm movement reflects the nature of the sheared flow through which the falling items descend, where the low-level wind direction veers with height.

Still another possibility is that the debris rotates around the mesocyclone as it is carried aloft. However, that a few items of debris fall out well to the right of the "storm direction" is worrisome, especially if one is attempting to predict the fallout of hazardous material.

The historical record suggests that fallout is mainly from thunderstorms that have produced tornadoes rated F3 or greater in intensity (though we must recall the uncertainties in the F-scale values when making this assertion).

Somewhat in contrast, our first-hand experiences in 1994 show that thunderstorms which have produced F2 tornadoes can also produce long-distance transport and fallout, a point that is only weakly indicated by the historical record. Indeed, it may be significant that we found long-distance transport and fallout in the first two F2 events we investigated, suggesting that perhaps these phenomena occur much more commonly than the historical data would suggest.

The number of events for which we have first hand data remains at two, a sample too small to fully answer the questions raised in Section 1.2.

We are hopeful of obtaining additional cases in 1995 with the second VORTEX intensive observing period.

Just before the onset of the spring storm season, we will also be advertising nationwide for reports of fallout, advising National Weather Service offices and media meteorologists of our project.

We close by noting that in addition to the interest inherent in these phenomena in their own right, lofting to high altitudes and long-distance debris transport by tornadic thunderstorms constitute challenges for numerical modelers to duplicate, and provide a unique means of testing certain types of cloud and mesoscale models.

Replicating observed fallout patterns will require combining the dynamics of a cloud model with a model for the aerodynamic behavior of "typical" debris particles.

It requires consideration of both in-storm winds and adjacent environmental flow.

However, simulation of fallout does not require a cloud model coupled with an aerodynamic model for the debris.

Rather, since debris should not significantly modify the wind field, one can run a cloud model through a storm's life cycle, then go back and use the resulting four-dimensional wind field to predict debris trajectories.

Such a simulation could become a prediction model for use by emergency management personnel.

Again, the high quality, temporally and spatially dense measurements of environmental conditions to be made during VORTEX should facilitate such research.

ACKNOWLEDGMENTS

The late Dr. Charles E. Anderson provided the inspiration for this work through his study of the Barneveld, Wisconsin tornado.

The historical review could not have been done without the extensive analysis of tornado records that has been carried out by Mr. Thomas P. Grazulis over the last decade.

Christopher R. Church, a partner in our field work, made useful comments on an early draft of this article and provided insights on how to interpret Table 1.

Mr. Michael Magsig and Mr. Carl Levison read several rough drafts and provided excellent sounding boards.

Special thanks are due Mr. Stephen Cale of the Durant Daily Democrat, and the other individuals who provided us with reports of debris and fallout:

Ms. B.J. Riggs; Mrs. Vernon Dunn; Ms. Renee Fair, WCM in the NWSO - Fort Smith, Arkansas; Mr. Steve Piltz, WCM in the NWSO - Tulsa; Mr. Jay Hilgartner, Meteorologist, KFSM-TV, Fort Smith, Arkansas; Mr. Fred Roush, MIC, NWSO - Fort Smith, Arkansas; J. D. and Linda Fite, Kiamichi Valley Gas Co.; Ms. Odell Mosley; Mr. Lloyd Swain; Paul and Stephanie Sidener; Mr. Lynn Colson; Ms. Maggie Hill; Ms. Betty Brewer; Mr. Cleveland Dennis; and Mr. Greg Stumpf of the NOAA National Severe Storms Laboratory. Dr. T.T. Fujita and two anonymous reviewers made several valuable suggestions that improved the final draft.

This work is supported by the National Science Foundation under Grant ATM9411767.

[APPENDIX]

REFERENCES

Anderson, C.E., 1985a: The fall-out pattern for debris for the Barneveld, WI tornado: an F-5 storm. 14th Conf. on Severe Local Storms, American Meteorological Society, Boston, MA. 264-266

Anderson, C.E., 1985b: The Barneveld tornado: a new type of tornadic storm in the form a spiral mesolow. 14th Conf. on Severe Local Storms, American Meteorological Society, Boston, MA. 289-292.

Corliss, W.R., 1983: Tornados [sic], Dark Days, Anomalous Precipitation, And Related Weather Phenomena. The Sourcebook Project, Glen Arm, MD, 196 pp.

Davies-Jones, R.P., 1981: Acquisition and analysis of severe storms and tornado field observations. Section 4 (pp. 21-66) of Summary of AEC-ERDA-NRC Supported Research At NSSL 1973-1979 (J.T. Lee, ed.), NOAA Technical Memorandum ERL NSSL-90, 93 pp.

Doswell, C.A. III, and D.W. Burgess, 1988: On some issues of United States tornado climatology. Mon. Wea. Rev., 116, 495-501.

Felknor, P.S., 1992: The Tri-State Tornado. Iowa State University Press, 131 pp.

Fujita, T.T., 1971: Proposed characterization of tornadoes and hurricanes by area and intensity. Satellite and Mesometeorology Research Project Research Paper 91, Department of the Geophysical Sciences, The University of Chicago, Chicago, IL. 44 pp. Fujita, T.T., 1973: Experimental classification of tornadoes in FPP scale. Satellite and Mesometeorology Research Project Research Paper 98, Department of the Geophysical Sciences, The University of Chicago, Chicago, IL. 15 pp.

Fujita, T.T., 1987: U.S. Tornadoes. Part One: 70-Year Statistics. Satellite and Mesometeorology Research Project Research Paper 218, Department of the Geophysical Sciences, The University of Chicago, Chicago, IL, 122 pp.

Grazulis, T.P., 1980: Indiana Killer Tornadoes, poster.

_____, 1993: Significant Tornadoes 1680 - 1991. The Tornado Project of Environmental Films, 1326 pp.

Hayes, M.W., 1927: The St. Louis Tornado of September 29, 1927. Mon. Wea. Rev., 55, 405-407.

The Oklahoma Daily, 1994: Tornado victims rebuild, recall. The University of Oklahoma Publications Board, April 27.

O'Toole, J.M., 1993: Tornado! 84 Minutes, 94 Lives. Databooks, 284 pp.

Peterson, R.E, 1993: Far-field tornado debris patterns. 17th Conference on Severe Local Storms, American Meteorological Society, Boston, MA. pp. 319-322.

Smith, H.E., Jr., 1982: Killer Weather. Dodd, Mead & Company, 224 pp.

Stanford, J.L., 1987: Tornado: Accounts of Tornadoes in Iowa, 2nd Edition. Iowa State University Press, 143 pp.

Tanner, R.W. (Ed.), 1990: Southwestern Nebraska Tornado of June 15th. Storm Data, 32(6), 25-27.

Walz, F.J., 1917: Tornado of March 23, 1917, at New Albany, Ind. Mon. Wea. Rev., 45, 169-171.

FOOTNOTES

* Corresponding author address: Dr. John T. Snow, College of Geosciences, The University of Oklahoma, Sarkeys Energy Center Suite 710, 100 East Boyd St., Norman, OK 73019-0628 [Return]

[1] Grazulis investigated accounts of tornadoes of F2 or greater intensity, and/or those which caused loss of life.

Further, he notes that in collecting data for his study, his focus was not on recording debris reports, but on estimating damage intensity to determine F-scale values. He recalls "...I noted debris carried > 5 miles [but] my focus was never on long distance debris. I passed over many more examples. I focused on heavy debris > 500 lbs. carried > 1 mile in my searches." (T.P. Grazulis, 1993, personal communication) [Return]

[2] We note that Corliss (1983) documents many "falls" of anomalous materials -- such as frogs and fishes -- from showers and thundershowers.

While many of these accounts are likely exaggerations or misinterpretations, there are enough reports to suggest such events to occur and that the underlying mechanism is related to that discussed here.[Return]

[3] It is probably safe to assert that most debris that is transported long distances lands in unpopulated areas or else is accepted as common litter.

It is likely most fallout is detritus and blends into the landscape.

Probably only a very few items, novel enough to excite curiosity with their appearance in the local environment, are reported.[Return]

[4] Here we denote positive angles as being drawn counterclockwise from the composite "storm direction", i.e., to the left of the "storm direction."

Negative angles are drawn clockwise from this composite direction.[Return]

ADDENDUM

Following the publication of this article in the Bulletin of the American Meteorological Society, we have continued to collect reports of debris fallout from around the country.

See the Addendum for the most recent findings.

FALLOUT OF DEBRIS FROM TORNADIC THUNDERSTORMS 2:
Examples from 1994 and 1995

1. INTRODUCTION

There is no question that strong tornadoes can loft debris high into the air, while their parent thunderstorms are capable of carrying the lofted material long distances (here "long distance" is defined as greater than 5 mi [8 km]).

Historical records of tornado events provide evidence of this phenomenon (Snow et al. 1995; see also Snow et al. 1996, this volume).

Each tornado season, a few reports of "sensational" occurrences of debris fallout have been brought to the attention of the media by persons in the general public who found debris and recognized it as being associated with a distant tornado.

Data obtained in this way is limited by the low probability of a discovery being made and reported, as well as the degree of attention given to the event by the media.

Furthermore, a report is often of limited scientific value due to lack of essential detail.

Even if these factors are satisfied, a report will often be only a local public interest story.

An historical survey gleans only a relatively few records (Snow et al. 1996, this volume).

Only 86 out of 12,651 tornado accounts during the period 1871 to 1990 included reports of long range debris lofting.

This implies a rate of just 0.72 lofting events per year.

Here we report on a nationwide effort to collect as many accounts as possible of debris lofting, transport, and fallout in 1994 and 1995.

We show that lofting, long distance transport, and fallout of debris from tornadic thunderstorms occurs more frequently than is suggested by the apparent scarcity of historical accounts.

Furthermore, we show that lofting can occur in conjunction with tornadoes of a wide range of intensity.

Even though this systematic study was probably not exhaustive, we did collect reports from 17 separate debris lofting events over two years, which is almost twelve times more than what the historical record would suggest.

This implies a serious bias in the historical record which must be quantified.

We hypothesize that lofting events occur very frequently but most often go unreported. It would seem logical that in the aftermath of tornado events which cause significant damage (and hence produce much debris), there should be an associated pattern of fallout which is determined by the dynamics of the storm and environment.

This presents a situation where the collection of data is most efficiently performed by a large number of people, covering the likely fallout area.

Since the beginning of 1994, we have utilized the following methods to help us engage the general public's participation in our data collection efforts: we let the public know of our interests through writing articles in general publications; sending informational letters to National Weather Service offices; creating a home page on the Internet (http://parker.gcn.ou.edu/Debris/Debris.html), and establishing a toll-free telephone number (1-800-3DEBRIS) to facilitate the reporting process.

For some tornado events which we learned had caused debris lofting, we followed up with a campaign for public assistance.

By alerting regional media and law enforcement agencies that a tornado had recently occurred which may have produced long range fallout, we were able to inform much of the public in the region that there could be tornado-related debris in their area, and that we were seeking reports.

This process significantly increased the number of items that were reported and sent directly to us.

The results of our efforts are listed in Section 2 below.

Of particular interest are debris items which can be traced back to source locations.

Examples are canceled checks, letters, receipts, and photos with names.

We received more reports of this kind than of any other type of debris.

For long range reports, traceable debris leaves little question as to the point of origin, unlike other debris, for which time of appearance is the only clue that relates it to the thunderstorm at all.

Furthermore, untraceable debris usually cannot be confidently associated with any part of a tornado, or even to the tornado itself (consider a report of a fallout of tin roofing material, or of tree leaves or limbs, etc.).

Knowledge of the source and end locations of a debris item, together with its fall speed and atmospheric wind data allow analyses to be performed to estimate a three-dimensional trajectory for the item.

Such analyses allow inferences to be made concerning maximum lofting altitudes and the point where debris makes the transition out of the storm environment. (Magsig et al. 1996, this volume).

2. CASE LIST

The following list illustrates the 17 lofting events which were reported to us since the beginning of our campaign in January 1994.

We adopt a format similar to one used by Grazulis (1993) in his Significant Tornadoes 1680-1991.

The first line of each event description denotes the state(s) involved, the date of the storm, the number of different locations (more than 8 km from the source) where debris was found, the farthest distance debris was known to be lofted (in km), and the highest F-scale intensity rating given to the associated tornado.

Where possible, the relationship between fallout locations and storm/tornado tracks are described.

Based on the work of Anderson (1985), debris is classified as either paper, light (1 pound), or heavy (1 pound).

3. CONCLUSIONS

It is very probable that the previous list contains only a small sample of the lofting events which actually occurred during the two-year study period.

Furthermore, it is certain that for each event listed, more long-range debris exists than was actually reported to us.

These conclusions are supported by the fact that the process of finding debris through public assistance becomes less efficient as population density decreases.

Often, in the Great Plains states, if a tornado strikes a populated area, and therefore has a high likelihood of producing lofted debris, the region downstream where fallout is likely is sparsely populated.

This "population effect" is illustrated by the Friona, TX, case of June 8, 1995 (Figure 1).

This case is unique because there is a highly populated area 100 km downstream from the damaged area.

We find that the greatest geographic density of long-range reports exists within the Amarillo, TX, metropolitan area, which is near the far end of the fallout plume.

Because our media campaign included both the metropolitan and rural newspapers throughout the region, we can assume that differing regional public awareness was not a major factor in the resulting report distribution.

This study further supports the idea that for long-range debris lofting to occur, a tornado need only be strong enough to produce considerable damage, and must strike structures containing loftable items.

Of the lofting events for which F-scale intensity were known, four were F2, four were F3, and seven were F4.

The orientation of debris items relative to their associated storm tracks or (if storm tracks were not available) tornado tracks was determined for each event above.

Figure 3 is a composite showing all debris items plotted against a single reference track.

Unsourced debris and debris from events for which no track information was available was excluded.

It is evident that most debris tends to land to the left of the storm/tornado track, with the fallout of heavier items generally being close on the left and paper items ranging from close on the right to distant on the left.

Figure 3 is consistent with a similar plot of debris accounts from the historical record (1871-1990) by Snow et al. (1995, 1996).

With the high space-time resolution data obtained by VORTEX during the Friona and Allison events (June 2 and 8, 1995), we hope to obtain more accurate wind profiles in the storm and near storm environments, allowing for more meaningful trajectory analysis.

Figure 3. Composite pattern of 84 debris reports associated with 13 tornadic storms in 1994 and 1995.

Arrow indicates reference storm track and has arbitrarily been oriented SW to NE.

Both the systematic collection of lofting accounts nationwide and the intensive study of a few well-represented events will provide a solid base on which to begin developing a numerical model to simulate the debris lofting, transport and fallout process.

Acknowledgments

The authors thank everyone who took the time to call or send in debris reports from around the country over the past two years.

Dr. Chris Church provided input on earlier drafts.

This work is supported by the National Science Foundation under Grant ATM9411767.

4. REFERENCES

Anderson, C.E., 1985: The fall-out pattern for debris for the Barneveld, WI tornado: an F-5 storm. Preprints, ,14th Conf. on Severe Local Storms, Indianapolis, IN, Amer. Meteor. Soc., 264-266

Grazulis, T.P., 1993: Significant Tornadoes 1680 - 1991. The Tornado Project of Environmental Films, 1326 pp.

Magsig, M.A., C.H. Levison, J.T. Snow, and A.L. Wyatt, 1996: Long range debris transport and fallout in Oklahoma from a tornadic thunderstorm on May 7, 1995. Preprints, 18th Conf. on Severe Local Storms, San Francisco, CA, Amer. Meteor. Soc.

Snow, J.T., A.L. Wyatt, A.K. McCarthy, E.K. Bishop, 1995: Fallout of debris from tornadic thunderstorms: An historical perspective and two examples from VORTEX. Bull. Amer. Meteor. Soc., 76, 1777-90.

______, 1996: Long range debris transport and fallout in the Ardmore, Oklahoma tornado of May 7, 1995. Preprints, 18th Conf. on Severe Local Storms, San Francisco, CA, Amer. Meteor. Soc.

FOOTNOTES

[*] Corresponding author address: Carl H. Levison, School of Meteorology, 100 E. Boyd St. Suite 1310, Norman, OK 73019-0628.[Return]

[1] This fallout pattern contrasts with that in the May 7, 1995, event (Magsig et al. 1996, this volume), in which all debris fell within 20 km of the reflectivity track. The 00Z upper-air sounding from Amarillo (approximately four hours after the tornado) indicated significant veering of the wind from southeasterly to southwesterly up to 700 mb. Soundings outside the storm environment depicted a more unidirectional wind profile from the southwest. The fact that the Friona storm turned towards the east after passing the city, along with the fact that the Amarillo sounding showed no westerly winds at any altitude, seems to suggest that debris which landed farther away from the storm track exited the storm environment at higher altitudes.[Return]

The last sentence in the Introduction should be omitted.

The third sentence of footnote 1 should read "Sounding outside the Ardmore storm environment..."

The last sentence of footnote 1 should read "The fact that the Friona storm turned towards the east after passing the city seems to suggest that debris which landed farther away from the storm track exited the storm environment at higher altitudes."

In the description of the Friona, TX, case, "cassette tape" should be changed to "strips of magnetic tape."

Other Debre Reports
Great Bend, Kansas Tornado of 1915

The Great Bend, Kansas tornado of November 1915 is the tornado which seems to have a greatest number of oddities associated with it.

Why? Who knows! It was an unusual time of year for a violent tornado this far west.

In fact, it is the latest date in the year that a violent tornado has ever struck the state of Kansas.

The funnel began its late-evening journey five miles southwest of Larned, 16 miles southwest of Great Bend.

It was visible only occasionally during the flashes of lightning.

The oddities began southwest of Pawnee rock where a farm was leveled to the ground and two people were killed.

From a short distance away, one could not tell that a farmstead had ever existed there.

Five horses were the only uninjured survivors. They were carried from the barn a distance of a quarter-mile.

All were unhurt, all were found together, hitched to the same rail.

At the edge of Great Bend, the Charles Hammond house was unroofed.

The family was completely unaware of the damage until they came outside to survey the neighbor's damage.

At Grant Jones' store, the south wall was blown down and scattered, but shelves and canned goods that stood against the wall were unmoved.

The Riverside Steam Laundry, built of stone and cement block, was left with only a fragment of upright wall, yet two nearby wooden shacks seemed almost untouched.

At the Moses Clay ranch, on the east edge of town, 1000 sheep were killed, the most ever killed by a single tornado.

A cancelled check from Graeat Bend was found in a corn field, one mile outside of Palmyra, Nebraska...305 miles to the northeast, the longest known distance that debris has ever been carried.

A "rain of debris," receipts, checks, photographs, ledger sheets, money, clothing, shingles, and fragments of books fell on almost every farm north and wst of Glasco, 80 miles to the northeast.

A necktie rack with 10 ties still attached was carried 40 miles.

A four-page letter "from a swain to his fair damsel in which he promised all" was carried 70 miles.

A flour sack from the Walnut Creek Mill was found 110 miles to the northeast, perhaps the longest distance ever recorded for an object weighing more than one pound.

Up to 45,000 migrating ducks were reported killed at Cheyenne Bottoms.

Dead ducks fell from the sky 40 miles northeast of that migratory bird refuge.

In Great Bend, an iron water hydrant was found full of splinters.

Mail was lifted from the railroad depot and scattered for miles to the northeast.

Some of it was returned to Great Bend, but some of it was sent on from where it was found... one of the earliest forms of air mail!

Farmers living two miles from town were unaware of the tragedy and were "dumb-founded" when they visited town the next day and "beheld the tragic spectacle."

Over 20,000 visitors viewed the wreckage the following Sunday.

Fictional oddities were added almost daily to the growing list of stories.

An iron jug was blown inside out... a rooster was blown into a jug, with only its head sticking out of the neck of the container.

May 7, 1995

The F3 tornado which struck north-central Texas and south-central Oklahoma on May 7, 1995 yielded over 50 reports of transported debris, many of which were reports of multiple items.

More than forty of the items have been traced back to their original location.

Debris from this storm was found in eight counties in Oklahoma, some as far away as 100 miles.

Some reports of interest include a man's jacket, transported nearly 20 miles from its source; a flag from a golf course, lofted 43 miles; and a canceled check lofted 125 miles.

Friona, Texas - June 2, 1995

On June 2, 1995, an F4 tornado struck the town of Friona, in the Texas panhandle.

Following this storm, we received reports of about 60 debris items being found at 19 different locations.

Most items were paper, including numerous canceled checks and receipts.

Light debris, such as a floppy disk, shingles, a cassette tape and plastic flowers (perhaps from the cemetery northeast of Friona) were also found.

The few heavy items found included pieces of sheet metal, a 5-by-3 foot sign, and a piece of wood from an airplane.

Many items were found more than 40 miles from their source locations.

Texas Panhandle - June 8, 1995

On June 8, 1995, a family of tornadoes, some rated as high as F4, struck the Texas panhandles towns of Pampa, Kellerville, and Allison.

Paper items such as canceled checks, receipts, photographs and business forms were found from all three locations.

Other items found include large pieces of styrofoam, insulation, and plywood.

Several items were found more than 60 miles away from their sources.