11 Aug 06
I met my new storm-chasing chums in Colorado, at the start of a six-day tour. All week I'd been accompanying them across Middle America as they searched for the ultimate prize: a tornado.
Surprisingly, they weren't the bleach-blonde adrenaline junkies you might expect. Indeed, most of them were middle-aged and reassuringly sensible. Like Colorado resident Jane Reller, who was celebrating her 50th birthday while on the tour.
'I've been fascinated by big storms since watching The Wizard of Oz as a kid,' she told me.
However, one person who I did suspect of being a closet mentalist was 68-year old Glen Nix. Having flown fighter planes in Vietnam, he didn't look like the type who got easily scared.
'I've flown straight through monsoons in combat situations, but I'm interested to see what they look like from the ground,' he said nonchalantly, standing before me in his requisite Ray-Ban Aviators and military-style crew cut.
The leader of our gang was Roger Hill - a qualified meteorologist and self-confessed storm chasing addict. Following a career in the air force, he turned a childhood fascination into a thriving business by becoming a guide and partner in Silver Lining Tours - an Oklahoma-based storm-chasing company that runs trips throughout the Midwest from May to July.
During this period every year, the area of Middle America known as 'tornado alley' - including the states of Kansas, Nebraska, Colorado and the Dakotas - comes under attack from hundreds of storms, which sweep across the region on a daily basis.
Many of them inflict huge damage on whatever gets in their path. However, they're not to be confused with the devastating hurricanes that caused so much destruction in Florida and New Orleans last year.
A hurricane is characterised by ultra-high speed winds that circulate around a centre of low pressure; on a photograph, this looks like a giant comma-shaped cloud, with a point ('eye') in the middle.
Meanwhile, a super-cell is a giant thunderstorm - around 15 miles across - containing a huge updraft of wind. This then forms an anvil-shaped cloud that bears similarities to the mushroom cloud generated by a nuclear explosion. When these up-flowing winds spiral out of control, tornadoes can form.
Not every super-cell produces tornadoes but nearly all of them contain massive hailstones - along with torrential rain, deafening thunder and spectacular lightning. Witnessing one is, without doubt, an awe-inspiring experience; getting caught in the centre of one is terrifying, as I would find out later in the week...
