Atlanta tornado one the most damaging on record

The strong EF2 tornado that smashed through downtown Atlanta at 9:40 pm Friday night is a reminder that the U.S. is potentially vulnerable to a very high death toll from a violent tornado hitting a major city. Friday's tornado, with a width of 200 yards, path length of 6 miles, and winds up to 130 mph, was strong enough to cause an estimated $150-$200 million in damage to downtown Atlanta. Only 16 tornadoes during the 20th century caused inflation-adjusted damage more than $200 million (Brooks and Doswell, 2000), so the Atlanta tornado is one of the most damaging of all time. Fortunately, no one was killed, although at least 27 people were injured, one seriously.

As unlucky as Atlanta was to have its first tornado ever to hit the downtown area, the city was extremely fortunate that the tornado was not not stronger. What would have happened if a clone of the strongest tornado on record--the May 3, 1999 Bridgecreek-Moore F5 tornado--had hit Atlanta? According to tornado researcher Josh Wurman of the Center for Severe Weather Research in Boulder and three co-authors in a paper published in the January 2007 issue of the Bulletin of the American Meteorological Society, the toll would have been staggering--14,900 deaths and tens of billions in damage. I discussed their findings in an April 2007 blog.

However, three tornado researchers, led by Harold Brooks of the National Severe Storms Laboratory, challenged these numbers in a January 2008 article in the Bulletin of the American Meteorological Society. They argued that Wurman et al. overestimated the potential deaths from such a storm by a factor of 100, and a death toll nearer to 150 would be more reasonable. They stated:

Given that the highest death toll in a tornado in U.S. history is 695 in the Tri-State tornado of 1925, and that the last death toll of greater than 100 was in 1953, the validity of these estimates is of some concern.

The authors conceded that a violent tornado traveling the length of a rush hour-packed freeway or hitting a sports stadium filled with spectators could generate much higher death tolls. Wurman et al. responded to the criticism by defending their death toll estimates:

We acknowledge that historical tornadoes have not caused the level of fatalities estimated in our paper. However, considering that tornadoes are relatively rare and that dense population in urban and suburban neighborhoods in the United States is a relatively recent but growing phenomenon, the historical record is too short to indicate the range of possible events.

Considering that Friday's Atlanta tornado hit the Georgia Dome stadium when it was packed with 16,000 people watching an SEC tournament basketball game, I think that both groups of researchers would agree that a death toll in the thousands was quite possible had the Atlanta tornado been an EF5.


Figure 1. Doppler winds image of the March 14, 2008, Atlanta, Georgia EF2 tornado. Note the region just northwest of the city showing blues and reds right next to each other, denoting strong winds moving both towards and away from the radar in a tight circulation. This is the signature associated with a mesocyclone--a rotating thunderstorm that commonly spawns a tornado.

More severe weather expected this week
Severe weather is expected over much of the Midwest and Southern U.S. over the next three days, in association with a strong cold front that will traverse the region. The Storm Prediction Center has placed portions of Texas, Oklahoma, Kansas, Missouri, and Arkansas under its lowest classification of potential severe weather today, "Slight Risk". The Weather Underground Severe Weather page and Tornado page are good places to go to follow this week's severe weather.

Good tornado book
For those of you interested in reading about the most violent and most damaging tornado on record, the famed 1999 Bridgecreek-Moore tornado, I recommend a reading of Nancy Mathis' book Storm Warning, which is now out in paperback. I reviewed the book in a blog last year.

Annual WeatherDance contest ready for registration!
Armchair forecasters, now's your chance to shine! WeatherDance, based on teams in the men's and women's NCAA basketball tournaments, allows players to predict which team's city will be hotter or colder on game day in each round of the Big Dance. Beginning today, players can make their forecasts at the Weather Dance Web site at: www.weatherdance.org. The site will be updated with cities promptly after NCAA seeding announcements. First round Weather Dance selections must be entered by 11:59 p.m. EST Wednesday, March 19.

"Officially, Weather Dance began as a class project to get students involved in weather forecasting, but we kept it around because it got popular. People think they can do better forecasting than the meteorologists. Well, here's their shot!" said Perry Samson, WeatherDance creator, co-founder of the The Weather Underground, Inc., and Professor in the Department of Atmospheric, Oceanic and Space Sciences at the University of Michigan.

This is the third year for the game. Last year more than 2,000 people played. Most play merely for the thrill, but many science teachers involve their classes as part of meteorology units. The winning teacher will receive an invitation and $500 to join the Texas Tech/University of Michigan Storm Chasing team this spring for a day of tornado chasing. Other winners will receive a Weather Underground umbrella or a copy of the book "Extreme Weather," by Christopher C. Burt.

Jeff Masters