Weatherwatch: tornadoes and trailer parks

A tornado touching down in Riverside, California. Those living in well-built houses have less to fear. Photograph: Michael Ritter/AP

Spring might sound appealing, but in trailer parks in the part of the southern US known as Tornado Alley spring is the start of a season of destruction. Twisters cause tremendous damage to trailer parks every year. Popular lore suggests mobile homes act as tornado magnets, and statistics seem to confirm this: almost 40% of tornado fatalities in the US are in mobile homes, although they are only 7% of housing. It has been suggested that this is divine judgment on immoral trailer park residents, but there are more physical reasons. Fragile, temporary structures are far more vulnerable than permanent brick-built homes. They do not have protective storm cellars, and can even be rolled over by a strong wind.

Permanent buildings also benefit from another defence. Tornadoes are fed by an inrush of air at ground level. Trailer parks offer little resistance to this, since they have one-storey buildings with flat roofs. Taller buildings create a significant amount of air friction, slowing the air flow and so choking off the tornado. In these conditions, tornadoes are short-lived and dissipate before they can do much damage.

Built-up urban districts do get hit by tornadoes, but the damage and loss of life is usually minimal. A series of tornadoes struck the Brooklyn and Queens boroughs of New York City in 2010, resulting in a death. This is a very low toll compared to what a single tornado can do in a trailer park.