The BBC's Simon Hancock has been chasing storms through "Tornado Alley", an area of high tornado activity that runs through the centre of the US. He joined a professional team which hunts out tornadoes using hi-tech gadgets.
DAY FIVE - JOURNEY'S END
It seems far longer than five days since I embarked on this storm chasing odyssey across "Tornado Alley" in the United States.
We had a feeling that this was going to be the day
In just a few days we've travelled more than 2,000 miles (3,200km), visiting seven, or is it eight, different states?
We headed out this morning from Kansas City, crossed the border to Iowa and then arrived in Nebraska where we spent the majority of the day.
As our tour director Brian later explained, storm chasing can be like a game of chess - it's all about thinking about the next move ahead and planning for how you think the storm will react.
CCTV shows a tornado crashing into an Iowa bank
From the start of the day, we knew from his demeanour that things looked good and even as we stopped to fill the van with petrol, the warm wind seemed to hint that it could be our lucky day.
As we travelled through Nebraska, we could see on the van's radar that we were approaching an area of high storm activity and the clouds were beginning to rotate in the air just above us as the different atmospheric influences wrestled with each other - a sign of tornadic activity but no guarantee as we'd seen previously.
Tornado wall clouds captured on film
This time though, you could just tell things were different. The light changed - eerily green on one side, orange on the other - as warm moisture was sucked in. It's hard not to say it looked apocalyptic.
We stopped to record the moment, but this storm was getting mean and heading right for us. We rushed back inside.
The storm chasing team have to move to safety
This was the real deal - a massive tornado was tearing up power lines evidenced by blue flashes on the ground. As lightning cracked all around, we got fleeting glimpses of its giant conical shape lit up.
This was no pretty photogenic tornado but an ugly brute which as Brian put it "was fixing to eat us".
When chasing storms you have to keep ahead of a storm's movement as once you get behind the chance of catching up is fairly slim. This storm was motoring at 40-50mph (60-80km/h), so we had to match it and of course storms don't need roads to drive along.
For the next three hours, we zig-zagged at high speed through the country lanes of Nebraska, keeping ahead and every now and again making a drive-by of the central vortex to see if we could get a good shot; but such was the ferocity of this super cell thunderstorm of which the tornado was part, the accompanying rain seemed to wrap it up like a shower curtain.
This is not unusual but we were frustrated after our initial sightings not to get a better view.
Perhaps it was as well though as while being lashed by hail and rain, lightning all around, we came upon the result of its work, being at this point just minutes behind.
Through the dim green light I could just make out a number of trucks tossed onto their sides, flattened buildings and trees stripped bare of all leaves and branches.
Tornado captured on film
The crazy thing was that even after we had called our day of storm chasing to a successful conclusion, we could not escape from its path.
Having dinner in Lincoln, Nebraska, the town was alerted to a severe storm warning and sounded its tornado sirens.
In the restaurant we looked at pictures of the damage on the news and knew that we had been fortunate to catch a glimpse of the tornado and even more fortunate to return with a greater appreciation of the awesome power that this force of nature can exhibit.
Overall Alan and I have had a great experience this week, one I hope we've managed to put across in this diary. Thanks for reading - hope to catch you in a super cell sometime soon!
DAY FOUR: GONE WITH THE WIND
Blue skies did not bode well for the tornado chasers
We awake to the one thing you dread when storm chasing - blue skies and sun.
Things are looking desperate, and after a quick conference it's decided that we will ship out to more promising Nebraska, some 15 hours away.
It's a "non-weather day" for us.
Even if you live in a high-risk tornado area, there's apparently only a 4% chance of being hit in your lifetime.
With news of the good weather, we began to think that the odds might be stacked against us, even as we travelled around the region actively searching the twisters out.
Storm chasing trips aren't cheap - a week like this can set you back as much as $3,500 (£1,800), but despite our luck so far, our fellow travellers - Neil and Sam, a couple from Portsmouth on a round the world trip, and Chris from Sydney - are in good spirits.
The storm chasers have not been disappointed
One of the most amazing things about travelling in our van is the number of looks you get from people who are scared that we're going in the same direction as them.
Every time we stop at a petrol station, we're approached by nervous looking travellers.
I've started called our tour director Brian the Fifth Horseman of the Apocalypse, such is the fearful reaction that greets the van.
On our journey, we make a stop at Altus, Oklahoma. Here, we met with the head of the town's emergency management who showed us around his HQ.
Lloyd, who is an old friend of Brian's, is responsible for co-ordinating the response to any disaster that might befall the area, which despite today's lull often means tornadoes.
Whenever a storm threatens, Lloyd deploys a team of volunteer storm-spotters to sit and watch its progress, radioing back their sighting.
Lloyd co-ordinates the response to emergencies
The network of spotters across this region is ultimately responsible for the storm warnings I mentioned the other day.
Lloyd is just the sort of thorough individual you want running a disaster emergency centre and kept repeating to us we should always have a plan whatever we're doing.
As we left, he gave us a weighty US government handbook explaining what we should do in the event of a nuclear blast and other scenarios.
One plan he would have approved of is having a bespoke storm shelter - an increasingly popular option around this region.
Before we began the tornado tour, we stopped in at a company in Dallas - Stormblocker - who for $6,000 to $10,000 (£3,000 to £5,000) offer a near bullet-proof room.
Shelters to weather tornadoes
Tomorrow marks the last day of the hunt and there is early word that Nebraska may prove to hold the perfect storm we've been looking for.
Here's hoping for some really bad weather!
DAY THREE: THE SOUND AND THE FURY
Driving through the eye of a storm
It is not often a seasoned storm chaser will admit to being afraid, but today our tour director Brian Barnes did just that during our search for the all-important tornado.
The experience happened just inside the Texan border as we drove right through the middle of a severe storm.
Hail battered the van
Rain and hail battered the van, while visibility was reduced to just a couple of feet, with our driver Paul often having to turn into the wind in order to keep the vehicle on the road.
Brian may have been nervous, but he didn't show it. It was only after dinner later that evening that we realised how close we had come to being tipped over as a result of the cyclonic activity that you get in the middle of a severe thunderstorm.
As one of the tour quite rightly commented: "Ignorance is bliss!".
Earlier, we had come very close to seeing our first twister, with weather conditions almost perfect, until another storm cell bowled into the one we were watching and ruined the moment for us - Brian explained what was happening in the video below.
Brian Barnes explains how a tornado could be about to form
Unfortunately, despite being subjected to the might of the storm, we were unable to catch a glimpse of that all elusive tornado.
Sunsets are spectacular in Tornado Alley
We did however see some hail - while it was not quite of the calibre of the baseball-sized hail that can occur during storm season, it would still be pretty painful if it landed on your head!
One curious feature of Tornado Alley is that while the sky on one side of you may be sunny and clear, the other side could contain a cloud straight from a Stephen King horror novel.
This was perfectly illustrated at the end of the day as we stopped to survey the storm damage in an Oklahoma field that had been hit by a twister just minutes before we arrived.
Facing the van was an amazing red sunset, while behind was one of the most intense lightning storms I have ever seen.
Storm lights Oklahoma sky
Three days down and no tornado yet but we do feel we are getting closer.
Maybe all we need is a little luck. Fingers crossed!
DAY TWO: A TERRIBLE BEAUTY
Kit for storm chasing
Note to self - if you are going storm chasing it might be a wise idea to bring a rain coat!
Today was the first real day of our mission to capture a tornado.
In an effort to travel in the tour van with as little kit as possible we took only the bare essentials to ensure we wouldn't leave our fellow chasers trying to avoid sitting beside us.
So far, tornadoes has proven elusive, but the team have witnessed beautiful sunsets
We headed off at noon and tour director Brian informed us that we would hopefully get some action later in the day around the Kansas area.
Part of the fascination with tornado chasing is the fact that they can be small, isolated events in a big area.
And as with a safari, you need to know what signs to look for - they need several meteorological factors in place to feed their energy-loving needs.
Knowing how they work and having the equipment to spot these factors is vital. Before we left, Brian gave us a tour of his arsenal.
Beautiful sunsets, but no tornado
So we were off, and we perhaps naively expected to see something immediately.
Brian hovered over his console the whole time, checking the data and listening to the localised storm warnings on his ham radio, which spoke of golf ball- and baseball-sized hail.
The team listened to warnings over the radio
After several hours of driving, we noticed a change in Brian's demeanour and an intense look of concentration on his face as he repeatedly scanned the skies - as well as his PCs.
He went very quiet.
We were in between two severe storms, and he thought there was a good chance of tornado development and didn't want to be taken by surprise.
He explained later that he was continually calculating escape routes in case the storm turned upon us. In the excitement of the moment it's easy to forget what you're dealing with.
Another reminder of our predicament came as our storm tracking took us through Greensburg, a town which was levelled by a ferocious tornado just last year.
Greensberg suffered enormous damage after being hit by tornado last year.
In the eerie light of the storm it looked like Armageddon.
But by the end of the day, while we'd seen amazing lightning formations, spectacular skies and a beautiful sunset - a tornado had proven elusive.
Tomorrow we depart early from our motel in Wichita to pick up the trail again. Here's to another wet and windy day!
DAY ONE: EXPECTATIONS AND NAGGING DOUBTS
BBC weatherman Daniel Corbett explains how tornadoes form
My colleague Alan and I flew into Dallas. As we picked up our rental car a video of an enormous tornado ripping up the land was playing on the news.
This surely augured well for our storm chasing trip - though Alan pointed out that celebrating this with the rental car company might not be the best idea.
This year's tornado season in Tornado Alley has been much more active than usual, some say because of La Nina conditions.
Almost every day in this region there have been countless stories of destruction, near misses and lucky escapes caused by these powerful meteorological phenomena.
We're hoping to catch a bit of this action.
This amateur footage shows that the tornado season is well under way (William Hark)
We arrive in Oklahoma City and meet up with our tour group.
The tour is being run by professional tornado chasers Violent Skies under the guidance of Brian Barnes. Brian's father was a storm chaser and now he works with a mix of hi-tech gadgetry and instinct built up over the years.
At our hotel base camp, Brian took us through some of the meteorological features that he uses to figure out just where the tornado might be.
The Violent Skies team explained the dangers of storm chasing
He explained that he gets up every hour during the night to check on just what the weather is up to, and warned us to be ready to leave at a moment's notice if he spotted a window of opportunity.
His briefing also left us in no doubt about the potential danger of storm chasing, a point echoed when we went to the bar later that night and again found wall-to-wall coverage of tornadoes on TV.
We also met some of the locals who couldn't believe that we were coming to chase tornadoes while they had spent their entire lives trying to get away from them.
I think it's fair to say they thought we were slightly odd in this respect.
While their comments and the amazing footage on the local news gave us hope that we might get to see the power of the storm, it also made us think twice about just what we had let ourselves in for.
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