Chicken twisters

Impenetrable thick black clouds, fierce lightning storms and grapefruit-sized hail stones. No, I'm not describing a typical British summer but the weather conditions which precede the birth of a tornado – one of Mother Nature's most destructive forces.

I am one of those nerdy people who don't just skip past the Discovery and National Geographic channels, but actually stops at them… and then watches programmes… entire programmes. It gets worse. I use Sky+ series link to make sure I never miss my favourite documentaries. I have well and truly turned into my dad.

I've recently been fascinated by programmes on tornadoes in the United States. I have been both enthralled by this incredible phenomenon of nature and horrified by the destruction they bring to people and property.

The most dangerous tornadoes frequently occur in the area of the US known as Tornado Alley. In general terms, Tornado Alley is a strip extending down the mid-west of the US stretching from North Dakota to the Texas panhandle. At it widest point, the Alley stretches between eastern Colorado and mid-Ohio.

Now for the techy bit (which I have no doubt overly simplified in my scientific ignorance).

Supercell thunderstorms (long-living thunderstorms with a continuously rotating updraft of air) can spawn the most violent tornadoes. Supercells are most common in Tornado Alley because it is here that the warm, moist tropical air from the Gulf of Mexico meets the cooler, drier air coming in from the Rockies. The warmer air is forced upwards by the cooler air and, as this rising air meets changing wind speeds and directions, if conditions are just right, the updraft will begin to rotate like a spinning top (a mesocyclone). A funnel cloud can reach out towards the ground from the bottom of a supercell and, if it touches terra firma, a tornado is born. I think I need a lie down after all that.

Whilst the subject of tornadoes is a very serious one, I couldn't help but smile at the following bizarre (but true) story I stumbled upon.

The damage descriptions of rural tornadoes will often make mention of chickens being stripped clean of every feather on their bodies. In 1842, Elias Loomis decided to use this seemingly innocent fact to grow his knowledge of tornado wind velocities. As you will read, he performed an experiment that left much to be desired in the control of experimental variables.

Loomis's eureka moment gave him the revelation that if he could learn the wind speed needed to de-feather a chicken, he would gain an insight into wind velocities inside tornadoes. Loomis knew the speed at which a cannon ball was propelled by a cannon – 341 miles per hour - and he made the leap that by firing a chicken out of a cannon, if it was de-feathered, it would be a good benchmark to measure tornado wind speeds. He was about to discover that there was a very good reason why the Spanish Armada didn't attack Britain's Navy with chickens.

Our hero pointed the cannon into the air, loaded it with his organic ammo and fired. The resulting explosion didn't just pluck every feather from the chickens, but also blasted their tiny little bodies into particles so small they were difficult to find afterwards. Predictably, his experiment ended with messy, and unreliable, results.

Tornadoes are classified according to the Fujita scale which measures their wind speeds. A F0 tornado will have wind speeds of 40 – 72 mph whereas a deadly F5 tornado will have wind speeds of 261 – 318 mph. It was a F5 twister which struck Moore, Oklahoma in 1999.

The F5 tornado was one of 66 tornadoes to touch down in Oklahoma state during a three day interval starting on 3 May 1999. Forty-eight people lost their lives during this outbreak and damage in excess of $1 billion was inflicted on local communities. This was the most prolific tornado outbreak in Oklahoma state history.

The power harnessed by tornadoes is quite incredible. There were reports that a tornado tearing through Broken Bow, Oklahoma lifted a motel sign and carried it some 30 miles before dumping it in Arkansas.

No doubt the Tindall family from Amherst, Kansas thought they had a lucky escape when their house was the only property on their block left unscathed by a tornado that ripped through their town. Their relief was short lived as their house was struck by lightning a week later and burned to the ground. You couldn't make it up, could you?

Wedged into a cramped minibus for six, long days with thirteen other bodies and covering, on average, over 500 miles per day. Stopping for short breaks to answer the call of nature and to load up on yet more junk food to keep you going. Leaving your dodgy looking motel at the break of dawn and arriving at a new one at around 01:00 am after a gruelling day. Getting up early the next morning to start all over again.

Sound like a blast? Well believe it or not, this is the description of a holiday adrenaline junkies pay good money to go on. Perhaps the only draw (and I can think of very few others) is that you may get the chance of seeing a fierce rotating grey funnel bearing down on you at some speed. Storm chasing tourism has arrived. Wish you were here?

Now those of us living in the UK may be counting our blessings that we don't live in Tornado Alley. But be afraid, be very afraid. The UK gets hit by as many as 100 tornadoes per year, but most go unreported. They tend to be a lot smaller than their American cousins, with much slower wind speeds. So you needn't be that afraid after all. Why did I ever make such a fuss?

Please excuse me. I'm off now to see if How It's Made has started on the Discovery Channel.