I received many thoughtful and passionate responses to my previous post regarding the upgrade of the El Reno / Piedmont /Guthrie tornado in Oklahoma to EF-5 based, in part on radar observations of 60 m AGL wind speeds. As I noted there/then, the EF scale, as was the F-scale before it is a damage scale, not a wind speed scale. Some have argued that, for this reason, actual wind speed measurements should have no bearing on the EF-scale rating, while others have argued that we should try to incorportate wind speed measurements in EF-scale ratings whenever they are available.
Let’s climb into our “way back machine” and go back to 1971. (Granted, this precedes my own birth by nearly a decade, but I digress.) Dr. Ted Fujita was motivated by the question, “How fast are tornado winds?” Doppler weather radar was still in its infancy, photogrammetry was only possible with high-quality, well-documented film, and in situ measurements of the winds were, logistically, all but impossible to collect (despite valiant attempts to do so). The way I see it, Dr. Fujita asked, “What evidence for wind speeds do tornadoes most consistently leave behind?” His answer: Damage. In 1971, in a paper proposing the Fujita scale, he writes,
“…one may be able to make extremely rough estimates of wind-speed ranges through on-the-spot inspection of storm damage. For instance, the patterns of damage caused by 50 mph and 250-mph winds are so different that even a casual observer can recognize the differences immediately. The logic involved is that the higher the estimate accuracy the longer the time required to make the estimate. Thus a few weeks of time necessary for an estimate with 5-mph accuracy can be reduced drastically to a few seconds if only a 100 mph accuracy is permissible in order to obtain a large number of estimates with considerably less accuracies… high wind-speed ranges result in characteristic damage patterns which can be distinguished by trained individuals with the help of damage specifications…”
Fujita clearly spells out his rationale for the scale; his strategy was to use damage as a proxy for wind speeds in the absence of near-surface wind speed measurements. Forty years later, thanks to innovations like miniaturized, in situ probes and mobile Doppler radar, obtaining near-surface wind speeds in tornadoes is not so far-fetched. Because only a handful of such instruments exist, and deployments are challenging (the presence of a mere tree or building between the radar and tornado can compromise the measurements), we are still not collecting near-surface wind speed measurements in tornadoes with any consistency. And, we are finding that the wind speed bins don’t always match up with the damage indicators in the EF scale.
In my opinion, this means the scale needs to be made more flexible, or possibly supplemented by a wind measurement-based alternative (i.e. two ratings, one damage based and one measurement-based). One could envision expanding the EF-scale into a second dimension (i.e. an EF matrix), the second dimension only expanded if reliable wind measurements (M) are available, and collapsed if they are not. The El Reno / Piedmont / Guthrie tornado would, for example, be rated EF-4 based on its damage, but M-5 based on the RaXPol wind measurements extrapolated to the surface via an objective method.
What I outline above is merely my own half-baked idea, and I am eager to hear other suggestions from people closer to the subject area. I am not a tornado damage expert; I am an observationalist. Keeping the damage-based scale certainly has its merit, primarily in the interest of maintaining consistency with the last 40 years of records (fraught with uncertainty though it may be; see Doswell and Burgess 1988). However, a blanket disregard for reliable remote or in situ wind measurements seems unwise, when obtaining tornado wind speeds was precisely Dr. Fujita’s objective.
PRELIMINARY DATA...
EVENT DATE: MAY 24, 2011
EVENT TYPE: TORNADO
EF RATING: EF-5
ESTIMATED PEAK WINDS (MPH): GREATER THAN 210 MPH
INJURIES/FATALITIES: UNKNOWN/9
EVENT START LOCATION AND TIME: 8 WNW BINGER 3:30 PM CDT
EVENT END LOCATION AND TIME: 4 NE GUTHRIE 5:35 PM CDT
DAMAGE PATH LENGTH (IN MILES): 75 MILES
DAMAGE WIDTH: UNKNOWN NOTE: RATING BASED ON UNIVERSITY OF OKLAHOMA MOBILE DOPPLER RADAR MEASUREMENTS.
I’m not certain if this is the first time mobile radar data have been used to upgrade a tornado rating, but it’s certainly an unusual occurrence. (If you know of such an instance, please post a comment!) EF-5 tornadoes are extremely rare events, mobile radar data collection in them, even rarer, and crucial near-surface wind measurements, rarer still. The Doppler velocities in the upgraded EF-5 tornado were collected at 60 m AGL, according to my former officemate and Ph.D. candidate, Jeff Snyder. Since RaXPol is such a new radar, he and other members of Howie’s team have been double- and triple-checking their measurements throughout the past week. So far, I’m told, the data are of reliable quality. But, the data will still have to be subjected to the scientific peer-review process in more formal studies yet to be composed.
Pseudo-RHI of (top) uncalibrated reflectivity factor and (bottom) Doppler velocities collected in the 4 May 2007 Greensburg, Kansas tornado. Note the weak-echo column down the center of the funnel, indicative of centrifuging of hydrometeors and debris. Also note that no data were collected at altitudes below 1.2 km AGL. From my Ph.D. dissertation. Data collected by UMass X-Pol.For comparison, on 3 May 1999, a DOW measured winds over 300 mph in the Moore/Bridge Creek, OK F-5 tornado. In a 2002 paper about that data set, it was noted that lofted/centrifuged debris could actually contaminate the velocity measurements near the surface. In the Greensburg, KS, EF-5 tornado, which I studied as part of my dissertation research, Doppler velocities exceeded 180 mph, but only well above the surface. (We deployed too far away from the Greensburg tornado to collect data in that crucial near-surface layer – see the figure at right.)
Remember that the EF scale is not a wind scale. The wind speeds are estimates based on damage (which is the only evidence tornadoes consistently leave behind for us to study), rather than the other way around. For this reason, there may be forthcoming disagreements as to whether Doppler radar measurements can even be used to make an EF-scale determination. Stay tuned…
* An explanation of the EF scale (and how it differs from the original Fujita scale) can be found here.
Correction: The Mulhall, OK tornado was F-4, not F-5, and the 300+ mph measurement was in the Moore/Bridge Creek, OK tornado. Thanks to Roger Edwards and Mike Coniglio for the corrections!
I first met Chris Novy upon relocating to Oklahoma back in 2002, first as the moderator of the wx-chase e-mail list, and later from his NSWW presentations on storm spotter safety. Chris is a multimedia wizard, an ethical chaser, and a tireless advocate for safe spotting. His video-rich presentations are always eye-catching, amusing, informative, and occasionally sobering. His message is always the same – no spotter report, no video clip, no smidgen of name recognition, is worth losing your life for.
Chris has gained some undeserved notoriety, chiefly for calling out famous storm chasers when they engage in unsafe and illegal behavior while chasing. Like a good journalist, however, he seeks to verify his sources, and often provides video evidence that he shot himself, unedited. Not surprisingly, his YouTube channel is stacked deep with abusive, ad hominem attack comments.
Chris was out spotting on Tuesday, 24 May 2011 in his car full of video gear, when he was manhandled by the titanic, rain-wrapped El Reno, Oklahoma tornado. By all accounts, this tornado was shrouded by opaque rain curtains, and so large as to be disorienting to those chasing near it. The way Chris tells it, he thought he knew where the tornado was moving based on previous radar images. But the storm hooked right and the circulation grew, dragging the huge tornado directly over Chris’ vehicle.
The irony of the predicament was not lost on Chris – “Mr. Spotter Safety” got his butt kicked by a tornado. Instead of retreating in humiliation, he recognized the opportunity for a profoundly teachable moment, “a personal story to share with others in training.” Two of his in-car cameras survived and recorded the entire incident. He posted some of his dashcam video on YouTube and posted his gripping first-hand account on wx-chase. In doing so, he made a point that he himself likes to make in his spotter / chaser safety presentations: There is no point in getting right underneath a tornado to get a “money shot,” because you can’t see a damn thing!
Not surprisingly, Chris has endured no end of additional villification and judgment, particularly from those who were already angry at him for calling out unsafe chase practices of others. He’s been variously accused of exploitation, fame-grabbing, and outright hypocrisy. (Commentators appear to willfully forget that Chris is not making a penny off the publication of any of this footage, because YouTube is free. Not to mention that his primary chase vehicle, “pimped out” with camera gear, was totaled.) In contrast, I find that Chris has been tremendously humble about his “near death experience.” He endures the slings and arrows because he feels that the potential lesson he can bring to spotters and chasers across the country is worth the abuse.
I applaud Chris Novy for sharing his harrowing experience, and for doing so quickly and with humility and maturity. I’ve always made a point to keep a respectful distance from tornadoes, but I’ve certainly learned from his experience that tornadoes must be given an even wider berth than normal when they are large, rain-wrapped, and difficult to see. Tornadoes look contained, and perhaps even a bit tame, on a television screen, but Mother Nature always has the ace up her sleeve.
I did not chase on 24 May 2011, a day that many Oklahomans will find difficult to forget. I had signed up months before for an NSF workshop entitled “Science: Becoming the Messenger.” My husband, in jest, admonished me for signing up for an all-day workshop in late May: “You just know there’s going to be a big tornado outbreak that day.” Of course, it was just as likely there would not be.
About week ahead of time, I could tell that an interesting weather scenario was, indeed, in the offing for 24 May. A trough was progged to slide out of the Rockies that Tuesday, and all the other parameters (shear, moisture, and lift) appeared favorable for a significant severe weather event. It looked similar to 10 May 2010, when a north-south oriented line of supercells swept across Oklahoma at ludicrous speeds (50-60 mph), forcing VORTEX2 teams to scramble to collect coordinated data sets. The NWS – WFO for Norman had been generating public information for days in advance advising people to be prepared for another tornado outbreak. With 10 May 2010 still fresh in the minds of many, and the tragedy at Joplin still in the headlines, Oklahomans took notice.
I am not one to cancel long-held plans based on forecast models for the next week; I’ve been burned more than once when such a setup unravels. In addition, one of the workshop presenters was Chris Mooney, one of my favorite bloggers and part-time host of the Point of Inquiry podcast (which I listen to with some regularity). In addition, I’d seen multiple tornadoes in southern Oklahoma the previous Saturday, a day when many others did not. So, I stuck to my guns and did not cancel my workshop attendance.
In the meantime, my husband was tapped to navigate the NOXP mobile radar for NSSL’s storm intercept team. (Don Burgess, the usual coordinator for that vehicle, was off delivering a keynote speech at the IEEE radar conference in Kansas City.) Before I left the house that morning, I left him a note on the mirror, wishing him good luck and many safe deployments.
When I arrived at the NWC, the NSF workshop organizers told us that the ~100 of us were going to learn how to craft messages for TV, radio, Powerpoint, blogs (hello!), and social media, including Twitter. Those of us with Twitter accounts were asked to “tweet” the workshop using the hash tag #nsfmessenger, which the organizers monitored from the front table. I’ve been using a Twitter accounts to reflect links to my posts on this blog, but on this day my Twitter feed veritably exploded with key points made by the organizers and presenters.
Just before lunch, a female researcher from Africa got up to practice her message that female African scientists are sorely in need of funding. She concluded with what she said was an old African proverb, “When you educate women, you educate a nation,” since women transmit their learning to their families and communities. I could not independently verify that this was indeed an African proverb, so I put quote marks around it before I tweeted it. The quote was re-tweeted, first by people within the workshop, and then by many more people outside the workshop. I got a few sarcastic tweets back to the effect of, “Umm, when you educate women, you only educate 50% of a nation, dumbass.” I chose to let these trolls stew in their own ignorance.
After lunch, awareness of the weather situation outside began to wax. I used the workshop hashtag to link other workshop participants to weather information. My attention became increasingly divided between the workshop presentations and radar images on my laptop showing a line of supercells taking shape in Western Oklahoma. The warning polygon colors quickly shifted from “severe thunderstorm” to “tornado” as spotters began peppering the maps with reports of wall clouds, funnel clouds, and finally tornadoes. Initially, all of the storms vectored past us to the north, but more convection took shape to our southwest, and one of the resulting supercells storms was aimed right at Norman One of the workshop organizers asked me if it would be safe for him to drive back to Stillwater. Initially I said yes, but after another KTLX volume came in, accompanied by a solid cluster of tornado reports crawling toward Guthrie and Stillwater, I changed my advice and told him to stay.
Mid-afternoon, I was astonished to receive an e-mail from Jon Hamilton of NPR, requesting an interview for a story about tornado safety. I e-mailed him back saying I was willing to do so, but that it would have to wait until tomorrow (Wednesday), and he agreed. (The interview took place on Wednesday and the resulting story aired on Thursday.) I’m just tickled that I was sitting in a workshop on how to communicate science to the media, and I got contacted by a member of the national media for an interview right in the middle of it! I did, indeed, fill out an “interview triangle” worksheet and had it in front of me while I was on the phone with Mr. Hamilton. I can only imagine that the workshop organizers were pleased to have this immediate feedback.
Around 4:00 p.m., the University of Oklahoma sent out a robotext to its staff indicating that the University was going to close at 4:30 p.m. Many offices, citing heightened awareness of the weather situation, had already sent their staff home. The workshop organizers suspended our activities. (I was just about to have a practice blog post vetted by Chris Mooney – darn!) Instead, I led Chris and some of the other NSF workshop participants up to the NWC observation deck to watch the storm move in.
There wasn’t much to see – just a boring gray veil of rain approaching from the west. I knew, based on RadarScope, that it presaged much worse things – like large hail. Then the tornado reports started materializing, some of which were from NWC staff and students out chasing. A tornado warning was issued that included the NWC, and the CSOs made a PA instructing everyone to move downstairs. I escorted some of the NSF workshop folks down to the first floor auditoriums, which I was astonished to find were almost entirely full already. People had brought in their families, dogs, cats, and even a few overnight bags to ride out the storm. Everyone had to sign in at the front door, per usual procedure. The rooms were orderly, but crowded.
Image from a camera mounted on the mast of the National Weather Center, which I believe shows a dissipating tornado to the southwest, over Goldsby/Blanchard. Image courtesy of P. Laws, K. Keys, and the OU College of Atmospheric and Geographic Sciences. Contrast has been enhanced to show the funnel.Once the NSF visitors (many of whom were from Washington, D.C. and other less tornado-prone locales) were ensconced below ground, I went back out to the atrium. Reports began to come in via TV and ham radio of a tornado southwest of the NWC. I briefly considered chasing in my own personal vehicle, but reports of rain-wrapped tornadoes all over the metro area made me hesitant to chase without an experienced partner in the passenger seat. Looking out the windows in that direction, I could see a barber pole updraft approaching the NWC, and hail that I estimate to have been 1″ to 1.5″ in diameter began clacking loudly against the NWC windows and skylights. I yearned to go up a floor or two to get a look at the sky over the trees, but decided to be a good role model and not create any more headaches for the CSOs, who were having enough trouble preventing curious people from wandering around.
I took a peek back in the auditorium, which by then was stifling and malodorous from the wall-to-wall hordes of anxious people and wet dogs. When reports indicated that the tornado southwest of the NWC had dissipated, some people tried to leave, only to be corralled back inside because the circulation reorganized to spawn another tornado east of Norman, near Pink, OK. When the “all clear” was finally given, the mass exodus to the parking lot reminded me of that after a major league sporting event. I applaud the CSOs for their calm handling of the crowds.
Do I regret not chasing on a “no duh” day when almost all of my friends went out and saw tornadoes? Yes and no. Each tornado is unique, and you never get the opportunity to see the same tornado twice. However, it was also a day that challenged even the most experienced chasers. A friend of mine (who teaches spotter safety) ended up in an extremely hairy situation when he unintentionally strayed too close to the Hinton / El Reno / Piedmont tornado. He was uninjured (thank goodness), but lost his chase vehicle and a large amount of camera gear as a result of the too-close encounter. I can’t help thinking that it could just as easily have been me, especially if I’d gone chasing alone.
Once the danger had passed, I got a text message from my husband that the NOXP radar had made a successful data collection on the tornado near Canton Lake, OK. (Link goes to my husband’s video.) Later, I learned that Howie’s group, operating the RaXPol and MWR, both collected data on the Hinton / El Reno / Piedmont tornado. While great / unique data collection can never replace people killed by this tornado outbreak, I hope that the research that results from those data will help to redeem some of the tragedy. It may never be possible to reduce the tornado fatality rate to zero, but little by little, we unravel tornadoes’ secrets.
Mr. Hamilton interviewed me over the phone for about 10 minutes on Wednesday morning. I’m glad that he picked up on the highway overpass myth (which I mentioned almost in passing) and used that as a key point. A lot of the other sound bites I gave him (about situational awareness, weather radio, etc.) were not used, but perhaps will be touched on in future pieces.
There’s a story behind this appearance, which I’m still writing up as part of my “log” of yesterday. More later.
To make a long story short: I did not go chasing because I was attending a workshop at the NWC, which let out two hours early. Lacking a chase partner, I stayed, and tried to keep the workshop organizers (many of whom were from NSF in Washington, DC) informed and helped funnel the attendees down into the tornado shelter when the warning was issued. (This was actually my first time being in the NWC during a tornado warning because, usually, I’m out chasing!) Judging by photos taken by a few people who snuck up to the NWC obs deck, the rope stage of the Chickasha/Blanchard tornado was visible for a few seconds. I missed it. The same supercell went on to drop another tornado east of Norman, near Pink, but I didn’t see that either.
My husband was out navigating the NOXP radar, and his crew collected data on the Canton / Fairview tornado. Jeff Snyder reported that he collected an amazing RaXPol data set on the Hinton / El Reno / Piedmont tornado. I have to admit to being more than a bit jealous!
I’m sure either of Dan or Jeff would trade in those data in a heartbeat to restore the lives of the tornado victims. (Five people are confirmed dead as of this writing.) Still, the data collection was a major victory for severe weather research, and hopefully the work that comes out of it will help to redeem some of the tragedy of today.
Update: Corrected locations where radars collected data.
I am dead tired right now, but wanted to put forth a frame grab showing a funnel cloud that we witnessed near Allison, TX, a few miles west of Denton, at about 7:43 p.m. this evening.Funnel cloud about 2 mi. S of U.S. Hwy 380 near Allison, TX, at 7:43 p.m. CDT. Video frame grab (contrast enhanced).
Dan and I went chasing with a colleague, Aaron, and his girlfriend Meredith. Our initial target was Ardmore, because we were working within some schedule limitations. However, convection near Jacksboro, TX tempted us across the Red River, and after ditching a wrung-out LP storm near Forestburg, we skirted around the forward flank of a right-turning supercell approaching Lake Bridgeport from the west. After several minutes on gravel roads, we caught sight of a lowering in the cloud base from the lake shore just north of Wizard Wells, TX. We were forced to escape southeast through the town of Bridgeport, TX as the storm turned hard right.
The north Texas storms had all had only tenuous grasps on supercell characteristics, and became increasingly amorphous as time went on. After calling the chase off, we drove east along U.S. Hwy. 380 toward Denton, TX. Meredith noticed a lowering to our south, which began producing tapered scud fingers, two of which were clearly funnel-shaped, appeared in the same place with respect to surrounding cloud features, and lasted 20-30 seconds apiece. We reported this funnel cloud at 0046 UTC, just south of Allison, TX. A TVS appeared in the exact same location, accompanied by a minimal hook structure, in the subsequent 0047 UTC volume from KFWS, providing validation of our observation. As my husband noted, sometimes you’re done with a storm, but the storm isn’t done with you!
As we drove north along I-35, I happened to catch on video a CG bolt strike about 1/4 mile from our vehicle. It clearly beaded as it dissipated, and can be seen near the end of the attached YouTube clip.
Tornadoes produced from the same synoptic-scale system devastated Joplin, MO and portions of my old stomping grounds in Minneapolis, MN. My heart goes out to people impacted.
For those who aren’t familiar, Rocky Rascovich’s annual chaser picnic in Piedmont, OK is a local institution. It usually occurs on a Saturday in May, when skies are blue and there’s nothing to chase. Not only does it give the local (and vacationing) storm geeks a place to hang out, eat some burgers (prepared by his industrious wife Dee), ogle each other’s chase videos, and compare stories from the past year, but it gives the chase tour groups something to do on a down day.
I woke up honestly not expecting to chase today, and busied myself preparing a dish to pass at the picnic. I was dimly aware that there was an SPC-issued slight risk and 5% tornado contour out to our east, but figured it was going to be out in the SE OK jungle. (I was a little jaded from our clear-sky bust on Wednesday.) As I hobnobbed at the picnic with Rocky, Chris Novy, Bill Hark, et al., we checked the SPC mesoanalysis page periodically, but assumed that the big show would be out east on I-40 on the progged dryline bulge.
We left the picnic around 5:30 p.m. and headed back toward Norman. Even as we left Piedmont, we could see a crisp updraft tower to our distant south. As we approached Norman, it hit the tropopause and began to spread anvils both upshear and downshear. The radar presentation on Dan’s Radarscope looked more and more supercellular, so we decided to blow by home and keep heading south on I-35.
New cauliflower updrafts continued to swell up the storm’s rear flank, and by the time we reached the Sulphur exit and headed east on OK-7, a funnel cloud and tornado report had appeared on Spotter Network. All our gear was still in my trunk, so we didn’t get any video until we stopped on the east side of Sulphur around 7:30 p.m. Almost immediately, we were rewarded with a funnel cloud, followed by a couple of brief condensation funnels near Hickory, OK about 10 minutes later, all of which Dan reported on Spotter Network.
After that, we lost about 30 minutes enduring a “bungle in the jungle” after trying to cut east from OK-1 to U.S. Hwy. 377 along an intermediate county road. I danced my Corolla around in the mud and forayed down a dead-end road that our mapping software indicated was continuous. (We passed several other chasers who were also led astray.) We lost our data feed while navigating the back roads, but eventually regained it when we emerged near Fittstown, OK. By then, our target storm was trending downhill, while a second storm near Ada, OK (whose initial convective towers we had bypassed on our earlier drive south to get to the Sulphur/Hickory storm) had exploded into classic textbook supercell structure.
Tornadic supercell west of Ada, OK on 21 May 2010. Remnant of tornado (bowl-shaped lowering) can be seen just above the red SUV in the foreground.We rocketed up U.S. Hwy. 377 to Ada, OK – a town perched on a hill – and a saw a magnificent, underlit supercell crown the rise. Rounding the west side of Ada on OK-3, we heard spotters on ham radio reporting a tornado in progress, and managed catch a glimpse of it near a power sub-station. Additional funnels formed and dissipated on the west side of town, but the low contrast from a descending reflectivity core made it impossible to say with certainty if any made ground contact, even when my video was sped up.
Once it grew dark, the Ada supercell filled in completely with precipitation, and its radar presentation began to deteriorate. We called the chase off, and drove home to radio coverage of the Oklahoma City Thunder’s unenviable 93-87 loss to the Dallas Mavericks (despite their best efforts). At least we had an unexpected “win” today: Not only did we see several tornadoes, but so far as we know, there were no damage or injuries resulting.
Update: My husband posted his “director’s cut” of our chase here:
When I was an undergraduate research assistant at the University of Wisconsin – Madison about a decade ago, I examined similar infrared satellite imagery for indications of drought. As we all learned in biology class, leaves maintain crucial range of moisture levels and temperatures in their interior largely by controlling water flux through their outermost few layers of cells. Tornadoes batter vegetation and shred leaves into tiny pieces, exposing their moist interiors. (I never saw the rain-wrapped 10 May 2010 Tecumseh, OK tornado pass by a few miles to my south, but shredded leaves rained down out of the sky for several minutes after it passed. I only see that kind of vegetation lofting in the immediate aftermath of a tornado.) If the plant isn’t killed outright, it becomes “stressed”, changing its reflectance characteristics at different wavelengths.
Healthy vegetation reflects strongly in the near-infrared wavelengths (around 0.9 microns), but stressed vegetation reflects weakly. In addition, stressed vegetation lights up in a band centered around 1.9 microns, as this diagram from NASA shows:
A logical “signature” for stressed vegetation, therefore, might be R(0.9 microns) – R(1.9 microns). When this value is positive, the vegetation can be inferred to be healthy. When it’s negative, indications are that the vegetation is stressed. This is likely not the exact formula used by the ASTER researchers; I just made that up on the spot. A robust index would be based on examination of many different wavelengths, different vegetation types, and over many seasons. (Obviously, this is not my area of expertise any longer!) One might be able to determine an optimal stressed vegetation indicator using a statistical technique like principal component analysis (PCA).
I remember seeing similar satellite images of the 3 May 1999 tornado damage swath through Moore. This paper, from Dr. May Yuan of the OU Department of Geography, contains prime examples. Neat stuff.
It is not often that you see a tornado in a densely-populated city (simply because cities cover such a small portion of the Earth’s surface), and can use surrounding buildings to gauge the size of the condensation funnel. The tornado appears to touch down in a park between the viewer and some multi-story apartment buildings that I estimate are about a mile away. The rapidly-rotating cloud base is about twice as high above the ground as the tops of the apartment buildings. One media report says that the visible funnel is only 20 stories, or about 50 m, tall, even though the rotating portion of the storm clearly extends much higher. According to the accounts I have read, no deaths or injuries resulted from this tornado, and the only reported damage was to a van.
