Although the 2014 tornado season kicked off with a whimper, not a bang, thanks in part to cool weather persisting across much of the United States, this past weekend was a particular violent one in terms of extreme weather, with twisters leaving behind them a sizable swath of destruction and despair across Arkansas, Iowa, Oklahoma, and beyond (and judging from reports out of Mississippi, this storm system is very much from done). At least 18 people, a majority of them residents of Arkansas, lost their lives in this weekend’s storms, the first reported fatalities in an otherwise quiet tornado season.

And while numerous “traditional” buildings and homes were leveled by this weekend’s deadly storm system, a handful of trailer parks were also destroyed including one in North Carolina that was “ripped to shreds.”

Trailer parks and tornadoes. Tornadoes and trailer parks. The famously abusive relationship between the two is one that has fascinated both the media and the public for decades — so why exactly have been trailer parks earned the "tornado magnet" label? Is the notion that trailer parks seemingly attract twisters, just a media-perpetuated myth and a particularly hoary pop culture trope? Or is there some truth to it?

Just days ahead of this weekend’s storms, researchers from Purdue University released the findings of a study that, with the aid of over 60 years of Indiana weather data released by National Weather Service’s Storm Prediction Center, somewhat demystifies the whole park-tornado thing, tired as it may be. And as one would suspect, it’s all about location.

In an effort to better grasp where exactly tornadoes tend to touch down, Purdue researchers concluded that twisters have a statistical preference for causing the most damage in so-called “transition zones” — geographic areas where two distinct types of landscapes meet and dramatically change. Examples include the fringe areas that fall between built-up suburban sprawl and rural farmland, dense forests and rolling plains. More often than not, these sparsely developed, lowly populated outskirts are where mobile home communities can be found in the greatest numbers.

According to the Purdue team's findings, between 1950 and 2012, 61 percent of tornado touchdowns in Indiana occurred within 1 kilometer of built-up urban areas. Forty-three percent of twisters touchdowns fell within a kilometer of heavily forested areas. In other words, primo areas for mobile home settlements.

This isn’t to say that tornadoes never strike cities and heavily populated urban centers (on occasion, they do) and that trailer parks are always located in transition zones. But the trend does shed light on why when many tornadoes strike, a trailer park or two on the far edge of town always seems to get hit and hit badly (the severity of damage has more to do with the construction of mobile homes and the fact they aren't anchored to the ground than geographic locale).

Speaking to CBS Chicago 2, the study’s co-author, climatologist Dev Niyogi, addresses the tornado-trailer park link: “That essentially goes to the heart of it. How do we make settlements or landscape more resilient, and clearly there might be ways that we can make our livelihoods and lives safer.” Niyogi suggests that planners should take heed when it comes to developing in transition zones, whether it be erecting cookie-cutter tract housing or permitting a large mobile home community. Sure, available land may be cheap and abundant in these areas but the risk for extensive property damage and the loss of life may be greater than it would be closer into town. 

So why then do trailer park-friendly transition zone with make for prime tornado touchdown areas? Based on data collected and examined by researchers, it may have to do with surface roughness — "an abrupt change in the height of land surface features" that fosters severe weather. Explains Niyogi: "We might need to pay more attention to areas where land surface features transition from rough to smooth, flat to sloped, or wet to dry. These changes in landscape may provide triggers for severe weather."

Elaborates study lead Olivia Kellner: "There are still many unanswered questions about tornado climatology, but what we're finding is that there may be a relationship between the Earth's surface and the atmosphere that contributes to where tornadoes tend to touch down."

The study, titled "Land-surface Heterogeneity Signature in Tornado Climatology? An Illustrative Analysis over Indiana 1950-2012", appears in Earth Interactions, a journal published by the American Metrological Society.

Via [CBS Chicago 2], [The Daily Mail]

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