Sometimes the tornado wins big

kw: book reviews, nonfiction, tornadoes, atmospheric science, meteorology, storm chasers, biographies

I've never chased tornadoes, but I have seen a few. The number is small enough to catalog:

• 1964, August, Cedar Point, Ohio: A squall line spit out seven waterspouts, one after another, that marched out of Sandusky Bay and crossed the Causeway and Chaussee between the amusement park and the city of Sandusky, then dissipated. Waterspouts are seldom stronger than EF0 or EF1.
• 1985, Summer (July?), Rapid City, South Dakota: 4 tornadoes, all probably EF1, touched down in and around the city. I saw two of them. Looking west out my back door, I saw a funnel forming, ran out to take a picture of it, then found it hard to open the door against the wind. My wife called me to the other side of the house. To the northeast, a tornado was on the ground right across the street, tearing up sorghum in my neighbor's field. It was moving east, and no houses were hit. Driving into town the next day, I saw three buildings. Two were untouched; the third, in between the others, had lost its roof, a metal roof which was curled up behind the building. The barbed-wire fence in front of the buildings was full of fiberglass insulation.
• 1990, Summer (August?), Stillwater, Oklahoma: I didn't actually see this one, it was wrapped in rain. I was visiting a friend when my wife phoned to say the tornado siren near our home had gone off—would I please come home? I kidded her, "It sounds like I am safer where I am, but I'll come right now." All the stop lights were not functioning, and nobody else was on the road. As I turned onto the main drag that runs north through town, it began to rain so hard there was soon surf in the middle of the street. When it began to hail, I turned into a parking lot up against a large store, to its south. I tuned to a Tulsa station (the local station was off the air), just in time to hear them say, "We have it on radar, it is crossing Perkins at McElroy." I said to myself, "That is where I am!" The store was on the southeast corner of that intersection. The tornado was actually half a block to my north, taking the top floor from a row of two-story apartment buildings and piling up their A/C units in land to the east. It also broke off a dozen or more power poles around ten feet above ground level, so it was a "skimmer", not quite on the ground yet. I saw all this after the sky cleared, about two minutes after the radio announcement. I made it home safely.
• 1994, June, near Colby, Kansas: We were on our way to Denver from Stillwater. Our son was 7 at the time. Highway I-70 had just hooked northwest, several miles west of Grinnell. Perhaps 10-15 miles ahead we saw a squall line dropping a tornado, which traveled across the road and then dissipated. Another soon followed, and then a third. Then the storm itself broke up. I had slowed down, expecting we might have to stop before getting near the storm. We got to that bit of highway about 15 minutes after the last tornado collapsed and the sky had cleared. There was about a half mile of wet highway, with some torn-up ground on both sides. These were probably EF1 tornadoes. Though that is "weak" compared to the monster EF4 and EF5 storms, an EF1 can still roll a car around until there is too little room left inside for you to stay alive.

What is the tornado scale? The "F" or Fujita Scale was developed by Theodore Fujita in 1971. It was originally a 13-level scale of wind speeds, derived by the formula (V = wind speed in mph):

V = 14.1(F+2)^1.5

Dr. Fujita didn't expect F numbers greater than 5 to ever be used. So far, none has. This formula produces this table of the minimum wind speed for each F number:

• F0 = 40 mph
• F1 = 73 mph
• F2 = 113 mph
• F3 = 158 mph
• F4 = 207 mph
• F5 = 261 mph
• F6 = 319 mph

The "EF" or Enhanced Fujita scale replaced the "F" scale in 2007, with the threshold velocities changed to account for improved research into the kinds of damage caused by various wind speeds. The six thresholds (there is no EF6 or higher) are 65, 85, 110, 135, 165, 200. There is no corresponding formula, but a geometrical analysis indicates to me that a theoretical EF6 region should begin at about 235 or 240 mph and EF7 at about 285-290. This is important for what follows. But let it be said, an EF5 tornado can rip the slab of a house right out of the ground, and even pull some basements up, so there is little point in assigning larger numbers without measurement. When a tornado leaves nothing behind but plowed ground, you're already off the charts!

The Man Who Caught the Storm: The Life of Legendary Tornado Chaser Tim Samaras, by Brantley Hargrove, is a very exciting, fascinating, and ultimately rather sad, biography of Tim Samaras. The author is an excellent journalist, who dug into his subject to the point that he participated in several storm chases with friends of Tim, and witnessed some awesome tornadoes in the process.

Tim Samaras exemplifies the self-educated genius. Classroom study was not for him. With his parents' encouragement, he began taking apart various appliances and electronic devices from an early age. Sometimes he could get them back together. By the time he needed paying work, he was such a valuable instrument inventor and repairman that he was hired in spite of having no college. He cut his professional teeth designing and running instrument packages that could, for example, measure the blast force of two tons of ANFO, the explosive that Timothy McVeigh used to destroy the Murrah Building in Oklahoma City in 1995 (an explosion I felt from 75 miles away).

Tim was also a weather fanatic, and took to storm chasing very early on, teaching himself the meteorological knowledge he needed to forecast where a storm would produce a tornado—or a row of them—and how powerful they were likely to be. From 1999-2001 he developed the HITPR, the first instrument package to survive a direct hit by a tornado core and record the central pressure and temperature profile. He called it "the turtle"; its shape was designed to hug the ground better and better as the wind grew stronger. Its first success came in 2003 in Manchester, SD.

Other successes followed, in spite that the funding he was able to attract was rather poor compared to some other "professional" groups. He continued to get measurements nobody else could get, right up until the end. This was in part due to his superior forecasting abilities, knowing which way a storm was likely to turn, so he could deploy one or more turtles (or successors thereof) and get out of there alive. In one case, the tornado core hit his device 15 seconds after he had turned it on!

His son Paul became a leading photographer and videographer for his work. Thus it was, that when his on-the-spot forecast was not spot-on, May 31, 2013, near El Reno, OK, he, his son, and a close friend, meteorologist Carl Young, were killed by an EF5 tornado. Its official wind speed, measured by others with radar near the time of his death, was 295 mph. The highest wind speed measured for the El Reno tornado was about 305 mph, the second tornado in history to exceed 300 mph. Here is where my estimates above are meaningful: if there is any meaning to the extrapolation I made, this was really an EF7 tornado, and by the older scale, nearly an F6. At the time Tim was killed, its "core" was 2.3 miles wide. The core is defined as the area within which wind speeds exceed 110 mph, at least for tornadoes EF2 and stronger. To people on the ground and comparatively nearby, who survived, it looked like an upside-down mountain, stuck in the Earth. To anyone closer than about a mile away from its outer edge, it seemed to fill from horizon to horizon, and hang overhead like a rippling cliff.

The following image, clipped from a YouTube video by Dan Robinson, shows the tornado from several miles away. Its visible funnel is "only" about a mile wide at this point, but the smaller funnel to the right is a suction vortex that shows the actual width of the whole storm. This vortex, if I read the book right, was itself moving around and around the core at around 100 mph, and had its own winds in the 150+ mph range. Thus the outer edge of that vortex—or one like it—would be the source of the extreme winds that approached and probably exceeded 300 mph.

Largely due to the work of self-educated engineer Tim Samaras, meteorologists and physicists are puzzling out the workings of these storms that produce most violent winds on Earth. RIP Tim Samaras and Paul Samaras and Carl Young. I am sorry you are gone. May your legacy continue. And much thanks to Brantley Hargrove for bringing their story to us, particularly folks who may never see a tornado for themselves.

Second twistiest

kw: weather phenomena, tornadoes, records

As my wife and I drove across Ohio and Indiana last Tuesday, 4/26/2011, we were listening to Kentucky radio stations and their almost continuous tornado warnings or reports. The following day, the 27th, we were able to hear a few more such reports, but went out of range before we got to Missouri. We were glad to be north of all the bad weather, but sorry for the people caught up in it, and we prayed for them. In more than 300 cases, the answer to such prayer was "No." That day marked the middle of a cluster of tornado outbreaks that may yet rival the Super Outbreak of 3/19/1974, the worst outbreak of the Twentieth Century. I have a few notes on that outbreak in a book review I wrote in 2007.

We did not know at the time the magnitude of the event. It may yet exceed some or all of the records set in 1974. The only record that is sure to stand is the 1925 record of nearly 700 killed by a single tornado, which also had a ground damage track nearly 220 miles (350 km) long. To compare:

1. Tornadoes – 1974: 148 in 18 hours. 2011: 211 in 48 hours, but it is not known if more than 148 occurred in any single 24-hour period.
2. Deaths – 1974: 300-330. 2011: 334 and counting, making it the second deadliest outbreak after the 1925 event.
3. Ground track – 1925: 219 mi (352 km). 2011 (Tuscaloosa-Birmingham tornado): 80 miles, in a supercell that produced tornadoes over a 380-mile (610 km) path, but no single track that exceeded the T-B tornado.

The Tuscaloosa-Birmingham tornado may also be the second widest recorded. Its damage track is 1.5 miles (2.4 km) at its widest, while the huge Wilber-Hallam tornado of May 22, 2004 was 2.5 miles (4 km) at its widest. Such tornadoes are almost as wide as they are tall; their tops are typically at an altitude of 3-4 miles (5-6.5 km) above the ground surface. The dynamics of such storms begin to approach those of hurricanes, which are considerably wider than they are tall.

There are the inevitable questions about global warming. One set of events does not necessarily signal a trend, but it is true that a warmer climate will have more energy available for producing extreme weather. The climate certainly is warming up, and human additions to the greenhouse gas budget are now known to be a factor. There is a price to pay for revving up Mother Nature!

How likely is an F6 tornado?

kw: analysis, tornadoes

Tornado season is upon us, or at least upon the central US. Though the stronger storms occur in July and August, any spring thunderstorm spawned by colliding air masses can produce a tornado. The more common thermal thunderstorms don't do so.

I got to thinking about the strongest storm possible, and I wondered if a tornado will ever be classified F6, or even greater. When Dr. Ted Fujita first devised the F scale, ranging from F0 to F5, he considered that an F6, which he called "Inconceivable Tornado", was probably not possible energetically. Thus the final scale stops at F5, which has no defined top wind velocity. In effect, F numbers greater than five were defined out of existence! Secondarily, the scale is based on the level of damage. Since an F5 typically leaves nothing behind but plowed ground, there is no way to determine after the fact whether the top wind speed was at the low end or high end of the "F5 window", or above it.

However, that hasn't stopped others from having a second look. The CSG Tornado Table returns to the original formula for the lowest wind speed for each F number:

V (mph) = 14.1(F+2)^1.5

The threshold for an F6 by this scale is 318 mph (511 kph). These folks extend the scale to F12 with a wind speed threshold of Mach 1, or 738 mph (1188 kph). You can make wind like that in a wind tunnel, but nothing even close has been observed in the natural atmosphere.

Let's review the complex way extreme wind velocity is produced.

This image, from Jon Merage's Gallery of weather photos shows a multi-vortex tornado, probably an F3, at a very early stage, before it picked up enough dirt to obscure its structure. Three of the sub-vortices Fujita called "suction vortices" can be seen.

The whirling air in a suction vortex can reach 100 mph (160 kph) relative to the center of the vortex. In the most powerful tornadoes, the main vortex's wind speed is 100-150 mph (160-240 kph), so the outer edge of a suction vortex—in an F5 that is standing still—can reach 250 mph. But they don't stand still. A typical tornado moves along at about 30 mph (less than 50 kph), but they can zoom across the landscape at 60-70 mph (95-110 kph), so it is possible for all these to add up to very local wind speeds as high as 320 mph (515 kph).

With this in mind, it is just possible that perhaps two storms in history reached F6 velocities. Thus, while such storms seem not just possible, but may be historical, they are very, very rare. What keeps the lid on?

There is a literal lid on the power of tornadic thunderstorms: the thickness of the troposphere. A feature of the largest thunderstorms that illustrates this visually is the anvil, shown here in a photo from Spacelab (see this WeatherQuestions item for more info). It shows the top of a thunderstorm that has bumped up into the stratosphere and been forced to spread out. In the troposphere, where all weather occurs, temperature nearly always decreases with altitude. Above this, the temperature in the stratosphere rises with altitude, which prevents rising air masses from rising further. The rising, moist air masses that spawn thunderstorms get their energy from the cooling with altitude, and are weakened when they hit the stratosphere. A very strong rising air mass may punch a kilometer or two into the stratosphere, but that's about the limit.

Will global warming increase the chances for more F5 storms, and possibly some F6-scale tornadoes? It is not likely. Ground-level heating will be the greatest at high latitudes, and there will be little effect nearer the equator. If anything, the troposphere might increase in thickness farther to the north, at the expense of the atmosphere near the equator, thus making the "tornado belt" wider but less intense overall. I am not sure the northern Canadians and Siberians (and possibly the gauchos in southern Argentina) will welcome a push of tornado-potential weather to greater latitudes. But it will take a lot of warming to make a significant difference in the extent of each continent that can support frequent tornadoes.

F6: possible? Yes. Plausible? Less so. Based on history, about one tornado per century just might qualify.

Spinning for science - and the rush

kw: book reviews, nonfiction, weather phenomena, tornadoes, storm chasers, memoirs

You don't have to be crazy to chase storms with Reed Timmer, but it sure helps. He exemplifies the X generation's emphasis on the X in eXtreme—just ask him—as he recounts in his new book Into the Storm: Violent Tornadoes, Killer Hurricanes, and Death-defying Adventures in Extreme Weather. Andrew Tilin is cited as co-author.

By my count, from 1998 onward, Timmer's storm chasing buddies have lost four autos, destroyed by hail or flood, and he has lost at least one and perhaps two of his own. His truck-based armored vehicle "Dominator" is probably next on the list, because he plans to drive it right into a tornado vortex. I haven't yet heard whether he's done so.

Reed Timmer appears in the Storm Chasers show on Discovery Channel. The ups and downs of his life that led to this gig are the subject of the book, which begins with his arrival in Norman, Oklahoma in 1998, where he studied Meteorology. He obtained Bachelors' and Masters' degrees there, and has begun PhD Studies, but is apparently still at work on that.

The book is his memoir of involvement with tornadoes, and a couple hurricanes, and of his career as a publicity hound, once he found that his videos were a salable commodity. His web site TornadoVideos sells plenty of videos. He is not much into still pictures, so I got this image from one of his rivals, who kindly supplies her copyright notice in the image; see Green Sky Chaser.

For geographic reasons, the United States great plains are Tornado Central, the location of Tornado Alley, where more than half of all the world's tornadoes occur (some sources claim 80%, but I think that is high). During the years I lived in Stillwater, Oklahoma, while I didn't see a tornado, I almost drove into one that was wrapped in rain. I believe that was in 1990, when one tore through the middle of town and caused a bit of havoc. The road leading north from Stillwater to Ponca City crosses the buckle of the tornado belt.

Four years later, on a family vacation, we saw one that looked a lot like this image, as we approached Goodland, Kansas from the southeast. It crossed the road about ten miles ahead of us, and the storm dissipated by the time we got there. I like to see a tornado over there, just close enough to see well, but that's it. Storm chasers like a more up-close-and-personal experience.

This "up close" element sets Timmer apart. He's managed to get himself inside a couple of F0 twisters (In yesterday's post I wrote that an F0 has wind speeds less than 73 mph or 117 kph or 33 m/s. That is almost enough to knock you off your feet, but not enough to pick you up. Anything stronger, you're not likely to survive). He thrives on getting close enough so the storm fills his video camera's viewfinder. As a result, he's obtained many dramatic videos.

The "up close" element makes more conservative storm chasers uneasy, even angry. Timmer is a maverick, and revels in it. While he frequently writes of his desire to improve the science, it is the adrenaline rush that drives him. Let's be clear, he is a scientist all right. He's simply one of the more colorful ones. I'd compare him with Robert Bakker, the paleontologist who did the most to popularize the more active, intelligent side of dinosaurs. If Timmer's swashbuckling style gets more people's attention, and particularly helps the denizens of Tornado Alley save their own lives, I'm all for it. I don't have cable TV, or I'd mark my calendar to watch the next episode of Storm Chasers.

Spinning up to speed

kw: weather phenomena, tornadoes

I am reading a book about storm chasing. I expect to review it tomorrow or the next day. As a preliminary, I'll review some technical points about tornadoes here, based on the tornado intensity scale developed by Ted Fujita, from F0 to F5. The wind speed cutoffs for each increase in intensity are

• F0-F1: 73 mph = 117 kph = 33 m/s
• F1-F2: 112 mph = 180 kph = 50 m/s
• F2-F3: 157 mph = 252 kph = 70 m/s
• F3-F4: 207 mph = 333 kph = 93 m/s
• F4-F5: 261 mph = 420 kph = 117 m/s
• Max measured: 318 mph = 512 kph = 117 m/s

Three of these are illustrated below. All the images are shown rather small; clicking on any of them will bring up a larger version.

An F0 tornado from Scenic Reflections. Most tornadoes are in this category. This kind of storm most "looks like a tornado", the tapering rope shape with a dust cloud at the bottom. They are seldom strong enough for the entire rotating wind funnel to fill with dust, though you can see dust wrapping around the funnel cloud for about half its height.

Stronger tornadoes look more menacing because they widen out with enwrapped dust. The funnel cloud is just the low-pressure center, where the cooling caused by the low pressure causes moisture to condense. Tornadoes only form in moist air, so the funnel cloud is a universal feature, whether visible or hidden by dust or dirt and debris.

An F2 tornado from TopCities. At ground level, the dust cloud is probably a quarter mile (0.4 km) across. With winds that exceed 100 mph by quite a bit, such a tornado will at least remove the roof of any house it happens to hit, and usually take down the walls also. While an F0 tornado is unlikely to flip a car over, an F2 will certainly flip it over, and may roll it quite a distance.

From here up the scale, tornadoes get more wedge-like. It takes a lot of suction to hold the funnel together as the wind speed rises, and the diameter grows proportionally. Tornadoes F2 and larger often have multiple vortexes, which will be discussed below.

An F5 tornado from Weatherzone. These are the insane kings of weather trouble. Wider at the base than they are tall, they are wedge-shaped and the debris funnel hides multiple "suction vortexes", as Dr. Fujita called them. The largest F5 track known was more than two miles (3+ km) wide.

These don't just roll cars around, they fling them like paper balls. I have seen an auto that spent a little time in an F4 or F5 tornado. It exemplified one weatherman's advice, "Get out of your car. When the tornado is finished with it, there won't be room inside it for you." The Chrysler was crumpled to the size of a Smart Car.

Hiding in a basement is not a certain path to surviving an F5, though it is your best shot. They have been known to clean out a basement, even ripping out part of the concrete walls.

A multiple-vortex tornado, probably of intensity F4, from Chase-1.com. The complex nature of the storm helps us understand how they can generate such high wind speeds, such as the 318 mph noted earlier. The major rotation of the storm is about 100-150 mph. This is the ground speed of the suction vortexes when the storm itself is stationary. The whirling of the suction vortexes about their own axes is another 75-150 mph. The outside edge of a suction vortex thus reaches 175-300 mph relative to the ground. Then when the entire storm picks up horizontal velocity, it can zip along at 25-50 mph, so total wind speeds of up to 350, and perhaps greater, are possible.

If you must try to survive a major tornado, the safest shelter is one of the totally buried steel shelters. I've never heard of a storm uprooting one of these. They are expensive, however, and when I lived in Oklahoma, we knew of only two people who had one. The next best is a specially built storm shelter in a basement room or near the center of a house. An above-ground storm shelter, however, is unlikely to ride out an F4 or F5 storm. Some things, you simply can't afford to prepare for. Then, your best defense is to be elsewhere. Anyone living in Tornado Alley who doesn't have a weather radio is a statistic waiting to be recorded.

The twistiest day

kw: book reviews, nonfiction, weather phenomena, tornadoes

Pre-post: This is my 400^th post!

F5 by Mark Levine chronicles the "Super Tornado Outbreak" of April 3, 1974. The whole title is F5: Devastation, Survival, and the Most Violent Tornado Outbreak of the Twentieth Century.

The "F" in the book's title commemorates Dr. Ted Fujita, "Mr. Tornado," who ranked tornadoes in six classes, F0 to F5. He is shown here at the University of Chicago, where he spent nearly fifty years, with a tornado simulation machine. He passed away nine years ago.

The 1974 super outbreak included tornadoes of all strengths, and six that were ranked F5. According to a modern revision of the scale, a "EF5" tornado has winds exceeding 200 mph (322 kph or 89 m/s). Fujita's original F5 ranking meant winds exceeding 260 mph (418 kph or 116 m/s). The modern revision was driven by the feeling (prejudice?) of many meteorologists that winds at ground level just don't get as high as Dr F believed...and he isn't here to defend himself.

Dr. Fujita surmised a rank of F6, with winds exceeding 318 mph (512 kph or 142 m/s). Since an F5 leaves little behind it but plowed ground, there is little likelihood that we could determine after the fact whether an F6 actually was present. All the wind speed estimates are based on damage to structures and trees, so there is a lot of possible variation.

This is Dr. Fujita's map of the outbreak, showing the ground tracks of all 148 tornadoes that struck that day. Detailed information, and this map, can be found at the April 3 1974 web site.

As a general pattern, the outbreak began to the northwest and moved to the southeast, and tornadoes tended to occur in groups that followed one another in a northeasterly direction. I saw such behavior twice, on much less desparate occasions, once in Ohio and once in Kansas.

On the latter occasion the storm itself, a large thunderstorm, was moving slowly northeast. It had a wall cloud and mesocyclone on its southeast side. A funnel would descend near the back edge of the wall cloud, move toward the front in a northeasterly direction, then lift. Sometimes the next funnel would appear while the first was on the ground. I saw five (fortunately F0 or F1) tornadoes in a half hour, from that storm. As that storm dissipated, another one formed to its south, but fortunately didn't grow nearly as strong, and spawned no funnels.

In F5 Mr. Levine focuses on two tornadoes called Tanner #1 and Tanner #2, numbers 96 and 97 in this clip from the larger map. They both swept through Limestone County, Alabama just after sunset. One mostly demolished Lawson's Trailer Park, the other crushed most of what the first had missed.

Tanner #1 was an F5, the other an F4, with winds only about 30 mph slower (48 kph or 13 m/s). Both made ground tracks about a third of a mile wide. The width of a tornado "on the ground" only roughly correlates with its strength. There are F0 tornadoes that get a mile wide, and F5 tornadoes that were no more than a quarter mile wide.

The widest ground track on record is 2.5 miles (4 km) for the F4 Hallam, NE tornado of May 22, 2004. However, radar measurements of the May 3, 1999 tornado at Mulhall, OK, also an F4, indicate damaging winds extended over a diameter of 4.4 miles (7 km), and the "hot circle", 1 mile (1.6 km) in diameter, had wind speeds exceeding 245 mph (400 kph or 110 m/s); that's EF5 by the new scale, F4 by the old one.

An F0 tornado like this one, and the F1 shown next, are more typically narrow at the ground, from 50 to a couple hundred feet wide (15-50m). Most of the tornadoes in the 1974 outbreak were in this range. Of recorded tornadoes in the Twentieth Century, 75% have been F0 and F1. However, F4 and F5, which comprise 5% of the total, account for 65% or more of tornado deaths.

When we lived in Oklahoma, there was a saying to back up the admonition to get out of your car when tornadoes were about: "When the tornado is done with your car, there won't be room inside for you." Having seen a car planted next to the road I took to work each day, well munged by an F1 tornado, I can well believe it.

An F1 tornado is an awesome beast. I can't imagine what it is like being close to an F4 or F5, but that is what happened to several dozen people who lived in the Athens-Decatur area of northern Alabama. Author Levine focuses on Limestone County, and on 25 residents who met Tanner #1 and/or #2, personally. Some didn't live through it.

Throughout the book, he presents vignettes from the experiences and memories of a young couple, high schoolers at the time, who married shortly after recovering from their injuries. Donnie and Felicia (neé Golden) Powers tried to get out of their car when the F5 roared up, but the wind at first held the car door shut. Then it ripped it off, blasted them both with debris, and blew then right out of the car. They were comparatively lucky. Some folks got out of their car and fled to a ditch. The tornado dropped the car on top of them.

By daylight, an F3 tornado like this is scary enough. In the dark just after sunset, the big F5 seemed to pop up right in front of Donnie and Felicia. Once a tornado has been on the ground more than a few seconds, it fills with dirt, and may also be wrapped in rain or hail.

The latter was the case when I almost drove into one, an F1 in Stillwater, OK over twenty years ago. The downburst that preceded it just about stopped my car, and the rain and hail that quickly followed kept me from seeing the funnel. Luckily it passed a quarter mile from me.

For the 36 people of Limestone County who died that night, there just wasn't anywhere to hide. Nothing above ground survived the winds and smashing debris they carried. As I mentioned earlier, an F5 leaves little but plowed ground behind, sometimes the slab. But I've read of instances where the wind plucked up a corner of the slab and extracted it also.

One family lost half its members when they crowded next to a heavy fireplace. The collapsing chimney crushed them. Some who were caught in the wind managed to hang on to the ground. Some were blown about, but landed alive.

The wide "wedge" of strong tornadoes hides a lot. Tornadoes of F3 and greater strength often have multiple vortices. Fujita called these "suction vortexes" and one of his publications has photos showing that there were ten in a single mega-funnel. This image shows a three-vortex funnel as it reaches the ground, before the details got hidden behind a shroud of dirt.

Levine interleaves stories of the time: Nixon was just about to cave in and resign; Patty Hearst, kidnapee or convert(?), was much in the news; and Alabama Governor Wallace's popularity was soaring even as he continued recovering from an attempted assassination.

But the consuming stories of the book are the person by person accounts of their experiences seeing, hearing, feeling, and mostly surviving having crossed paths with the most ferocious windstorms of which this planet is capable.

Tornadoes and Their Groupies

kw: book reviews, tornadoes, storm chasers, weather phenomena, global warming

Mark Svenvold, Fordham University's Poet-in-Residence, spent a summer traveling with veteran storm chaser Matt Biddle, logging 6,000 miles in May, 2004. His book Big Weather: Chasing Tornadoes in the Heart of America (Henry Holt, publisher)s not so much a chronicle as a memoir and meditation. The book has copious endnotes and a good index, but no bibliography.

The first half of May that year was quiet, quiet enough to drive hundreds of storm-chasers half crazy. The second half was anything but. May 22 produced the Hallam, NE tornado, which basically plowed a furrow some sixty miles wide, and as wide as 2.5 miles, the widest on record.

Mark and Matt didn't see that one. The account in the book is from several eyewitnesses (and some scar-witnesses). But they saw plenty of others.

With the phenomenon of storm-chasing, quite a number of allied subjects fall under scrutiny: the classes of chasers (from yahoos to scientists), the advent and rise of the Weather Channel, and possible influences of global warming among them. Actually, it seems in retrospect that a third of the writing is polemical, intended to convince the reader of the reality, not just of global warming, but of human causes thereof.

Plenty of ink, and several photos, goes to Sean Casey and his "Tornado Intercept Vehicle" (TIV), a homemade tank weighing over six tons. Mr. Casey doesn't fit any other category, but is serious enough, and has learned enough, to earn the respect of the operators of the Doppler-on-Wheels (DOW) trucks from the Center for Severe Weather Research.

He was preaching to choir in my case. But I'm one who sees more benefit than loss in that equation. I know the math better than most. We know CO2 has about doubled since 1850. We can figure it has resulted in about a degree or two (F; or half to 1 deg C) of warming. Most of this has been polar. In temperate latitudes, the main effect has been greater variability: longer, warmer spring and summer, colder but shorter winter, with more violent storms more common than before. If the amount of CO2 were increased ten times, the maximum warming would be 4-6 deg F (2-3 C), so there's a limit to what will result just by our burning stuff.

There's just enough photography to whet the appetite. To see more, there are plenty of web sites with thousands of pictures. The cultish reaction many chasers have to images and video of tornadoes prompts the author to call it "torn porn." Probably apt. We tend to be drawn to destruction, and nothing causes greater levels of localized destruction than a tornado. A really big one, an F5, leaves only plowed ground. There's plenty to like about Big Weather.

Tornado Stories

kw: tornadoes, personal experiences

I've been reading a book about tornadoes and tornado chasing. I'll review it soon. It reminded me of experiences going way, way back.

I first heard a tornado story from my grandmother. Her family lived in Wichita, Kansas when she was young. One sunny day, a storm blew up rather suddenly. The young girl, exploring in a hidden corner of the yard, didn't respond to being called right away. A hard wind prompted her to go around to the front of the house, trying to find people—everyone had vanished. She sat on the porch, looked across the street, and saw a neighbor's house shatter apart. The tornado lifted at that moment, and roared right above her. She looked up inside the funnel. She told me it was blue inside, rather bright against the dark sky.

I've heard from others that tornadoes that arrive in dry weather have a lot of lightning with them, including inside the funnel. Some tornadoes are visible after dark for that reason. I have only seen tornadoes in moist or rainy conditions.

As a child, growing up in the arid Southwest, I often saw dust devils. We kids would pretend they were mighty funnel clouds, and imagine being carried away like Dorothy, to Oz. On a few occasions I ran right into one of them. Once it was strong enough to give me a spin and sit me down. I never tried running into one that was carrying a few tumbleweeds, though!

I first saw (nearly) the real thing when I was in High School. I was working at a resort on Lake Erie. One afternoon a big storm protruded a wall cloud, then, one after another, seven waterspouts formed over the lake, spun ashore, and broke up. They were about half a mile away, no more than fifty feet across just above the water line.

I went to graduate school in Rapid City, South Dakota. We lived East of town. People boasted that the city had never had a tornado within city limits. You could see, though, on aerial photos (I was a Geology student) several scars of tornadoes that had knocked over swathes of trees in the Black Hills. One day, the boast became outdated. A huge storm system blew up, with wind of all kinds, but little rain. I looked out my back door and saw a funnel cloud forming, several miles away. I ran outside to photograph it. About then, a blast of wind blew me right back through the open door, into the house. It was the inflow from a nearby tornado. From the front door, we watched a tornado tear its way across a sorghum field, hoovering up about a third of my neighbor's crop. It was later determined that four tornadoes passed through the city that day.

Many years later, living in Oklahoma, I nearly drove into one. Oklahoma twisters tend to be rain-wrapped. Anywhere within a half mile of them, you can't see them. I was at a friend's house, about 5 pm. My wife called to say the tornado siren had gone off (I could hear it over the phone), and would I come home Right Now! Foolishly, I agreed...there was no siren howling near where I was. The traffic lights were all out, so I figured it had already passed on. I found out later, the town power came from the West, and the wires went down ten minutes before the storm arrived. I remember turning North onto Perkins, the main street toward home. It began raining buckets, and blowing hard. Within seconds there was surf in the middle of the street. When it began to hail, I whipped into a parking lot and drove to the lee side of a warehouse market. I'd been trying to find a radio station that was working. Just as gravel from the building's roof began falling on my car, I got a Tulsa station. I heard, "...we have it on radar. It is at the intersection of Perkins and McElroy." I though, "That's where I am!" A minute or two later, the wind began to drop. Within ten minutes the sky was blue, except in the East, where the storm was receding. I had to go around the rest of Perkins Avenue, because there were wires lying in the street. The power poles had all been broken off about 15 feet above the ground, and the upper floor of a 2-storey apartment building, right across the street from my shelter, had been removed. It seems the tornado wasn't quite on the ground when it went by me, about 100 yards away.

Five years later, we took a driving vacation through Kansas, Colorado, Wyoming, and South Dakota. On the road going West toward Goodland, Kansas, we saw an isolated storm get organized about twenty miles further on. Goodland was another twenty miles beyond that. It was similar to the Ohio experience, but not waterspouts. There were five tornadoes in all, and for several minutes at a time there would be three on the ground, apparently following the same track. About the time the one in front broke up, another would form at the rear. They looked like small tornadoes, perhaps F0; I don't think they were as big as F1. See The Fujita Scale of Tornado Intensity. Regardless, I slowed down, not wanting to get there too soon! After about fifteen minutes, the show was over and the storm broke up. Another fifteen minutes, and we drove by, seeing only a few "drag marks" on the ground showing where the funnels had crossed the highway.
The following year, we moved to the East Coast, where tornadoes are not impossible, but very scarce. Funny, though, we liked Oklahoma a lot, and talk about returning when I retire.