Edited Version of March 21, 2001 Transcript
EIIP Virtual Library Presentation
"The Forgotten F5: The 1998 Lawrence County Supercell "
Meteorologist, National Weather Service
Moderator, EIIP Coordinator
The original unedited transcript of the March 21, 2001 online Virtual Library presentation is available in the EIIP Virtual Library Archives (http://www.emforum.org/vlibrary/livechat.htm). The following version of the transcript has been edited for easier reading and comprehension. Typos were corrected, date/time/names attributed by the software to each input were deleted but the content of questions and responses are as stated by each participant. Answers to participants questions are grouped beneath the appropriate question to facilitate meaning.
[Opening / Introduction]
Avagene Moore: Welcome to the EIIP Virtual Library!
Our topic today is "The Forgotten F5: The Lawrence County Supercell during the Middle Tennessee Tornado Outbreak of April 16, 1998." The paper is the result of the research of four gentlemen from the Warning & Forecast Office in Nashville, Tennessee: John D. Gordon, Bobby Boyd, Mark A. Rose, and Jason B. Wright.
We appreciate Mark Rose for being here today to present the results of this collaborative effort. Mark is a meteorologist at the National Weather Service Office in Old Hickory, Tennessee. Mark has authored or co-authored many technical papers, including publications in Weather and Forecasting, National Weather Digest, and the National Weather Association's Electronic Journal of Operational Meteorology.
Please help me welcome Mark Rose -- thank you for joining us today, Mark. I turn the floor over to you now.
Mark Rose: Hi. Thanks for having me.
On April 16, 1998, a tornado outbreak struck middle Tennessee. More than 20 supercells were identified by radar, and 12 tornadoes were confirmed -- the fifth largest tornado outbreak in middle Tennessee's history. The Warning & Forecast Office (WFO) in Old Hickory (OHX) issued a record 200 severe weather warnings on April 16, including 106 tornado warnings, in less than 18 hours. The Nashville metropolitan area was struck by three tornadoes --- one rated F3, and two rated F2. The F3 hit the downtown area.
However, the most violent and dangerous tornado of the entire event, the Lawrence County F5, was nearly forgotten.
There may be two reasons why the Lawrence County tornado did not receive the attention of the Nashville tornadoes: 1) it struck four remote counties in southwest middle Tennessee, and 2) a major metropolitan area (Nashville) was hit by three tornadoes.
The resulting intensive media coverage of the Nashville tornadoes simply overshadowed the impact of F5 winds in rural Lawrence County.
Official National Weather Service (NWS) records, obtained from the Storm Prediction Center (SPC), in 1999 listed three F5 tornadoes in Tennessee since records began in 1950. Extensive research by the authors has shown that these three ratings are likely erroneous. The lead author worked extensively with the SPC to consider downgrading these three F5s, which occurred in 1952 and 1974, to F4 ratings.
Besides discussion of the Lawrence County F5 tornado, this forum will include proposals to downgrade the three former F5 tornadoes, and why the authors feel the Lawrence County F5 tornado of 1998 is the only legitimate F5 in Tennessee history.
On April 16, 1998, Nashville became the first major U.S. city (:100,000) in nearly 20 years to be struck by an F2 (or larger) tornado in the downtown area. Shreveport, LA took two direct hits in 1978: April 17 (F2) and December 3 (F4). On the morning of April 16, local media began continuous live coverage of the tornado outbreak. This coverage rapidly intensified to a national level when Nashville was struck by an F3 tornado in the downtown area at 3:30 p.m. All three national news networks either led off with coverage of the Nashville tornadoes or reported it during the first five minutes of the newscast. The local, state, and national news justifiably focused on the Nashville tornadoes, thus greatly overshadowing the Lawrence County F5.
Around daybreak on April 16, showers and thunderstorms from west Tennessee and northern Mississippi moved into southwest middle Tennessee. This convection left an "outflow boundary" across Wayne and Lawrence Counties of southwest middle Tennessee. We hypothesize this boundary played a significant role in the formation of the Lawrence County tornado. The severe thunderstorm that spawned this tornado formed over McNairy County (3 counties west of Lawrence). The storm rapidly developed.
The initial tornado warning for Wayne County (1 county west of Lawrence) was issued at 3:43 p.m. Seven minutes later, an F4 tornado began 11 miles south of Clifton in Wayne County. The tornado was one mile wide at times, tracked 23 miles in Wayne County, killing 3 people, and injuring another 6.
Please note that 3 tornadoes are being tracked simultaneously, with the Lawrence County storm in full force. The initial tornado warning for Lawrence County was issued at 3:56 p.m., with the storm crossing into Lawrence County at 4:15 p.m. Based on aerial and ground storm surveys, the tornado intensified and produced damage, including some F5 damage, for 50 additional minutes. This one-mile wide violent tornado struck largely rural areas of Lawrence County for 23 miles. Fortunately, no one else was killed, although an additional 21 persons were injured. I have two damage photographs for you to load.
It completely leveled many well constructed homes, wiping the foundations clean, debarked several trees, and hurled a one-ton pickup truck more than 100 meters, all of which are described as F5 damage. Overall, the storm tracked 62.5 miles across Wayne, Lawrence, and Maury Counties before lifting. In addition to the 3 fatalities, 35 injuries occurred across the 3 counties.
According to the SPC database there have been three F5 tornadoes in Tennessee.
The first occurred on March 21, 1952 in Marshall County, Mississippi, and Fayette County, in west Tennessee, which is one county east of Shelby County (Memphis).
The second and third F5s occurred in Lincoln and Franklin Counties in middle Tennessee during the Super Outbreak of April 3, 1974.
One of the co-authors, the legendary Bobby Boyd, who worked the Super Outbreak as a radar operator, questioned the 1974 ratings. Mr. Boyd's thorough memory of the 1974 Super Outbreak led to a chain of events that shifted the scope of the paper. The paper's original focus widened from a case study to include a detailed examination of former F5 tornadoes in Tennessee.
"And now for a short history lesson "
In 1973, Fujita and Pearson created the F-scale for rating tornadoes. A few years later, Dr. Schaeffer at the National Severe Storms Forecast Center (now the SPC) hired over 50 college students to rate tornadoes that occurred prior to the NWS F-scale implementation. One student was hired per state, except Texas, which required several students.
The 1952 storm was rated by a student who used such data as photographs, newspaper articles, and information from emergency management. The storm originated near Byhalia, Mississippi and ended near Moscow, Tennessee. The college student rated the storm F4 in Mississippi and F3 in Tennessee. However, the SPC database showed this storm as F5.
Mr. Boyd conducted an independent survey of the 1952 storm, much like Grazulis. Mr. Boyd traveled to Fayette County, visited several newspaper offices, and the Tennessee State Library and Archives in Nashville. The only evidence that might suggest the possibility of an F5 was a reference in the Memphis Sommerville Gazette of a "concrete block building being destroyed." Based on newspaper accounts not indicating "incredible damage" in Fayette County, the authors believe the concrete building referenced was probably not a steel-reinforced structure. The authors concur with the student analyst and Grazulis.
Mr. Boyd was the primary radar operator at the Weather Service Meteorological Observatory at OHX during the super outbreak of 1974 and vividly remembers the event.
From discussions with several NWS employees, including the former state climatologist, the authors were unable to locate anyone who recalled whether the NWS had performed a storm disaster survey in middle Tennessee. However, Professor Fujita and some of his graduate students performed both ground and aerial surveys.
Furthermore, the authors researched several newspaper articles and pictures and spoke with the Lincoln County, TN Emergency Management Agency. All articles the authors researched indicated F3 and F4 damage in Tennessee and Alabama with both tornadoes. In fact, there was "devastating damage," including well-constructed homes leveled, steel structures badly damaged, and many deaths.
However, the authors were unable to locate reference to the "incredible damage" that results from an F5. The authors sent a detailed letter to the SPC recommending the two tornadoes from 1974, and the 1952 tornado mentioned above, be downgraded to F4. The SPC agreed to all three of these changes. The SPC database now reflects the conclusions of Professor Fujita's map of 1974, and Grazulis' 1952 tornado write-up.
In conclusion, the April 16, 1998 tornado outbreak was a wake-up call to most of the nation. Tornadoes can hit large metropolitan areas. In fact, Nashville, the nation's 16th largest city, was struck by 3 tornadoes. The authors suggested that the three former F5 tornadoes in Tennessee should be reclassified as F4. These changes have been adopted, making the April 16, 1998 Lawrence County tornado the only documented F5 in the history of Tennessee. This concludes my presentation.
[Audience Questions & Answers]
Avagene Moore: Thank you, Mark, for a fine presentation. As a citizen of Lawrence County, TN, I remember the F5 all too well although I was several miles south of the tornado's path. We now invite your questions and comments.
Amy Sebring: Besides correcting the technical record Mark, do the authors hope to bring more attention to this F5 in general? Since it did not get that much attention in the media at the time?
Mark Rose: Amy, that is the whole purpose of this paper. This makes the seventh time our study has been presented. The paper is also being published in the National Weather Digest, which is circulated all over the country. Keep in mind that there were no studies done on the Nashville tornado.
Avagene Moore: I might add that the paper was presented in our community just a few weeks ago.
Roger Fritzel: Is / was Grazulis the student assigned to research Tennessee.?
Mark Rose: Roger, actually Tom Grazulis is a college professor. He spent more than a quarter century of his life researching tornadoes. He published a comprehensive book a few years ago with the results of his study. He also encouraged us to pursue certain avenues to have the SPC database corrected.
Regina Blissett: That tornado was absolutely unbelievable. How wide was it? What is the history of other F5's in our nation?
Mark Rose: Regina, it was a mile wide at its worst. The history of F5's in the U.S. is that they are very rare and very deadly. The full version of our paper mentions some former F5's that have occurred in recent years.
Judy Jaeger: Do Tennessee tornadoes typically stay on the ground as long as this one? (Our Georgia storms occur and disappear in less than ten minutes.)
Mark Rose: Judy, tornadoes in Tennessee typically do not stay on the ground that long. I don't know how many have tracked for 62.5 miles but they are certainly very rare. As you say, they usually come and go in 10 to 20 minutes.
Amy Sebring: It appears that there was a substantial lead in the warning time from Wayne County. Is this attributed to the Doppler technology? Did the warnings make a difference do you think; that is, are they taken seriously?
Mark Rose: Amy, thank you for asking that. The Doppler technology DOES give us the ability to give large lead times on warnings, especially large supercells like the Lawrence County storm. People react to warnings differently. Because Lawrence County has such a history of severe weather, they tend to take warnings more seriously, whereas others do not. It also depends on how the warning is worded. A warning that says "Doppler radar indicated a tornado", will be taken less seriously than one that says "A large tornado has been sighted near Lawrenceburg".
Avagene Moore: Re: the F5 tornado -- as a lifelong resident of this county, it is still very startling to me to see where the tornado passed over certain roadways. The wooded areas are gone and the whole area very different. And yes, people here do take the warnings very seriously.
Amy Sebring: Has the Nashville event made a difference in the emphasis in Tennessee, re: preparedness and mitigation for example? If you know.
Mark Rose: Amy, funny you should mention that. The National Weather Service has implemented a program called "Storm Ready", where a town or city takes certain measures of severe weather preparedness, and is certified by the NWS as being "Storm Ready". Nashville is the first city in middle Tennessee to be certified.
Richard Foltman: Mark, 1) What are the estimated winds with an F5? 2) Should windows in office buildings in cities be laminated?
Mark Rose: Rick, the estimated wind speeds with an F5 are 261 to 318 mph. As far as laminating windows, I don't know how much good that does. And with an F5, it doesn't matter what you do.
Judy Jaeger: Are Safe Rooms or storm shelters prevalent in Lawrence County? There is so little you can do to mitigate tornado damage.
Mark Rose: Judy, I'll let Avagene answer that.
Avagene Moore: Judy, I don't think there are many Safe Rooms at this point but there is a gentleman here who is selling concrete storm shelters and doing quite well. The whole idea has been sold to the community as a necessity. We are believers!
Amy Sebring: Just wanted to mention that we had a previous session on the StormReady program with John Ogren who is here today. For further info, see <http://www.emforum.org/vclass/000308.htm> .
John Ogren: Or go to <http://www.nws.noaa.gov/stormready>.
Amy Sebring: Regarding tornadoes hitting metropolitan areas, the Fort Worth tornado was after Nashville, I believe. How did that compare to the Nashville event, if you know?
Mark Rose: Amy, I believe the Fort Worth storm was an F2, but caused more damage in the downtown area than in Nashville.
Judy Jaeger: What happened to the windows in Nashville office buildings?
Mark Rose: Judy, many of them shattered. Downtown was completely closed to traffic the following day. The cleanup took some time, with all the glass.
Judy Jaeger: Several years ago, we stopped telling folks to tape their windows in the face of hurricanes, because flying shards of glass were worse than flying bits of glass.
Mark Rose: I would have to agree with that. In high winds, windows are going to get blown out anyway, no matter what you do. I guess its better to have a window shatter than to have it flying through the air intact.
Amy Sebring: Mark, you mentioned that you and the other authors have been presenting these findings. Do you plan to collaborate in the future, have further study ideas on the drawing board so to speak?
Mark Rose: Amy, there was a second study done by me, one of the meteorologists who worked the event, and an engineer named Tim Marshall. We took some of the Doppler radar imagery, with radar-estimated wind speeds, and did a correlation between wind speeds, and damage. A link to the abstract of this study can be found at <http://www.srh.noaa.gov/bna/research.htm>. However, no further plans are in the works for another research effort. We will always be willing to present our findings. And I have never been involved in a project that has gotten as much airplay.
Avagene Moore: Mark, we all know that warnings are critical. In your opinion, what should cities like Nashville and Lawrenceburg promote for the best, timely warnings? I remember Nashville pushing sirens. I have mixed feelings about sirens.
Mark Rose: Sirens are fine in small towns, where everybody can hear them. But in big cities, I don't know. Sometimes they can be unreliable. Of course, we always promote NOAA Weather Radio as being absolutely the fastest way to receive severe weather warnings.
Amy Sebring: Has the Fujitsu scale stood up well over time? Has it proven useful? Can it be improved?
Mark Rose: Amy, as far as I am concerned, the Fujita scale cannot be improved upon. There are always ideas floating around about how it can be fine-tuned, but it has proven a very reliable scale of tornado intensity.
Tom Heath: The 'hooks' on fig 2 are very distinct. How good a predictor are they?
Mark Rose: Tom, hooks, at least very distinct ones as shown in the figure, are quite reliable. Before Doppler technology, hooks were the only method by which tornado warnings were issued by radar. But now, we don't usually issue radar-based tornado warnings without looking at a storm's wind profile.
Richard Foltman: Mark, should the use of spotters be emphasized?
Mark Rose: We cannot over-emphasize the use of spotters. They are our best means for gathering information about storms in progress. One of the things we stress in spotter presentations are what we, the meteorologists see (radar images), and what the spotter sees (actual storms, tornadoes, hail, wind damage, etc.).
Don Hartley: Sirens should only be one of several components of a warning package that includes, EAS, NOAA Weather Radio, faxes and pages, etc. Sirens are a particularly political thing here in West Alabama. After our killer F4 in December every neighborhood wants one. But Mark, I'm more concerned by automated radio stations that don't carry local severe weather EAS activations. During our tornado warning some members of the public report that a couple of stations never carried the warning. That's a real weakness in the warning chain.
Mark Rose: Don, indeed. Our warnings always carry the phrase "EAS ACTIVATION REQUESTED" as part of the header. Of course, radio and TV stations are not required to carry our warnings. But, I think it is a good policy, as it is a matter of public service. Again, that's why we always push NOAA Weather Radio.
Amy Sebring: See also the Storm Prediction Center site at <http://www.spc.noaa.gov/> that has very dramatic photos of tornadoes at the moment. For a tornado FAQ sheet see <http://www.spc.noaa.gov/faq/tornado/>. The F-scale is found at <http://www.spc.noaa.gov/faq/tornado/f-scale.html>.
Avagene Moore: Thanks, Amy. Mark, closing remarks?
Mark Rose: Well, again thanks for asking me to do this. I enjoyed the Q & A session. I wish you all the best.
Avagene Moore: Thank you very much for being an informative presentation, Mark. We appreciate your time and effort on behalf of the EIIP Virtual Forum. Please stand by a moment while we take care of a couple of announcements.
Next week, Wednesday March 28, 12:00 Noon EST, the Tech Arena features a session entitled "Emergency Management Content and Collaboration: Incident Master Portal Fills The Gap." Our special guest speaker will be James W. Morentz, Ph.D., CEO, Essential Technologies, Inc. Please mark your calendar and make plans to join us next week.
Audience, we appreciate your presence and participation today. We will adjourn the EIIP Virtual Library at this time. Please feel free to express your personal appreciation to Mark Rose for his presentation.