Back on June 24, 2012 a tornado, associated with Tropical Storm Debby, moved through Highland County, Florida. Very tragically, a young mother was killed protecting her baby from the violent wind that struck her house. The baby still wrapped in her mother’s arms suffered broken ribs, cuts and bruises, but did make a full recovery.
That tornado death was the last one reported in the United States until last Wednesday’s severe weather that hit northern Georgia particularly hard. An EF-3 rated tornado moved through Adairsville, Georgia killing a man when a tree fell on a shed he happened to be seeking shelter in. That stretch of 220 days was the longest stretch between tornado deaths in the country since such records have been kept in 1950.
The previous record was 197 days which occurred from late 1986 through early 1987. That period many of you will recall was also a period of drought and the corresponding lack of thunderstorms in the United States.
After a fairly fast start earlier in the year, tornadoes have been uncommon for the past several months. After the large tornado outbreak in the central plains from April 13-16, the tornado season quickly went quiet. Since then, the number of tornadoes recorded in the United States has been less than 50% of average.
Plus, those numbers are based on preliminary counts and the actual number official numbers are almost always even lower. So far this month, only 2 tornadoes has been reported in the country. The lowest July total on record (good tornado records only go back to 1950) was back in 1950 when just 23 tornadoes were observed. Considering that almost 100% of tornadoes are currently reported which was not the case back in 1950, that record may be hard to break.
Fewer tornadoes would generally be thought of as a good thing, yet, the overall lack of thunderstorms attributing to fewer tornadoes, is one of the leading reasons why many parts of the country are currently experiencing drought conditions.
After a spring with a very high number of tornadoes across the South, and a scary wind storm with tornado warnings here on May 30, a lot of people have a renewed fear of tornadoes. Like fear of flying, spiders, or snakes, a fear of tornadoes is based in a genuine danger.
However, in many people, this fear is heightened unrealistically during stormy weather. This unrealistic fear turns tornadoes into a mysterious, almost evil force in our minds. So maybe a little tornado reality will help. First of all, tornadoes are nothing but wind and wind is nothing but moving air. Any column of rising air, from a dust devil to a hurricane, rotates. A tornado vortex is a secondary circulation caused by an irregularity in a larger circulation found in some strong thunderstorms called a mesocyclone.
Two-thirds of tornado deaths are caused by EF4 and EF5 tornadoes, which comprise just 2 per cent of all tornadoes. The vast majority of tornadoes do not kill people
In many different statistical categories, 2011 is turning into one of the worst years on record for tornadoes. April set the record for the most tornadoes with 875 reported across the nation. Tornado numbers in May are still preliminary, but the national total for 2011 so far is already approaching the three-year average over an entire year and it isn?t even June yet. There have been an unusual number of large and violent tornadoes and several have hit large population centers including Tuscaloosa, Birmingham, and Joplin, resulting in some 500 deaths so far this year.
But before jumping to the conclusion that we now live in a new and terrible tornado regime, consider that tornado activity had been below average for several years in a row. Consider also that, historically, there have been years with high tornado statistics from time to time. Much like the wild hurricane season back in 2005, the U.S. is having a really bad time with tornadoes this year.
But it is likely just a bad year and not a foreboding change.
When I was in graduate school, one of the tornado disaster scenarios that was frequently mentioned was a F4 or F5 tornado moving through the Dallas/Fort Worth area during rush hour. With tens of thousands of individuals in grid-lock on the freeways with no shelter available, it was theorized that hundreds of individuals could die in such an event.
At the time it opened my eyes to the possibility of a mega-tornado disaster in an urban setting. If memory serves, a made for TV movie or documentary of such a scenario was made a few years later. Then, on May 3, 1999 a large tornado ripped through portions of Oklahoma City clearly demonstrating that such a disaster was more likely than many imagined.
Large tornadoes are always rare, plus the odds of one striking a densely populated area is always low, but this tornado season has sadly reminded us that as urban centers expand, so do the odds of additional tragedies occurring in the future.
The recent devastating tornado outbreak in Alabama raises concerns about building codes. The fact is, several of the Alabama tornadoes were EF4 (166-200 mph) or EF5 (200 mph or more( and it is simply too cost-prohibitive to design regular homes to be able to withstand such forces.
However, 98 per cent of all tornadoes produce damage in the EF0 (65-85 mph), EF1 (86-110 mph), EF2 (111-135 mph) or EF3 (136-165 mph) range. There are things builders can do to make houses reasonably safe from these winds, particularly EF2 and below, which is the most common. Houses that explode in a tornado do so not because of pressure, but because the roof is blown off and the walls fall down. In a well-built home, joists are attached to the walls with steel joist hangers instead of a single nail, and the walls are attached to the foundation with heavy anchor bolts.
Such homes will sustain damage in a tornado, but should avoid total destruction in all but the worst of storms
One of the most common threads on the Internet in recent days has been about how could so many people in 2011 die in a tornado outbreak? Before the advent of advance radar coverage and our current warning system, tornadoes would frequently cause the deaths of 100s of people each year. But in recent decades deaths from tornadoes have dropped dramatically until recent events.
The exact reasoning will take time to resolve as data and surveys are taken in the coming weeks. Yet, there are likely some root causes. First, the tornadoes and severe weather the previous day and earlier in that morning cut power to thousands of residents limited their access to the warnings that day. Second, the tornadoes were moving exceptionally fast with forward speeds around 50 mph. And lastly, EF-4 and EF-5 tornadoes are almost indescribably powerful and when mixed with an urban setting, the setup for a disaster is always going to be present.
The first decade of our new century recorded a noticeable decrease in violent tornadoes in the United States. The second decade so far has not been so kind. Although through this writing it was not official, the first EF-5 tornado in three years and only the 3rd in the past decade may have been recorded this past Wednesday. The horrific tornado outbreak that struck Mississippi, Alabama and Georgia killed over 200 individuals with over 1000 people injured.
That would place this event with the third highest death toll in the past 50 years. Several long-lived tornadoes with damage paths over 50 miles long, with widths near 1 mile, devastated numerous communities as well as portions of the larger cities of Birmingham and Tuscaloosa, Alabama.
EF-4 and EF-5 tornadoes are rare, but when they occur, high casualty numbers are frequently observed, because even if you take proper shelter, some storms are sadly just too powerful to survive.
Although the southern portion of the United States does have a second severe storm season in October and November, in most of the country, the summer storm season is winding down. As of this writing, 850 tornadoes have been reported in the United States so far this year, whereas in 2008, 1691 tornadoes developed.
This has been a significant drop over not only last year, but the past several years when the seasonal average has been around 1300. The overall cool spring and summer seasons over the eastern half of the United States were not as conducive to severe weather this year as it is in a more average year. Although you can never blame one factor for changes in weather, the transition from the La Nina conditions in the Pacific Ocean the past few years to our current weak El Nino probably played at least a small role in the quieter storm season experienced this year.