Factual error: Notice that all of the cars passing and honking at them have the same horn that sounds like a 70's import, even when some of them are pickups and larger cars.
Continuity mistake: When the red truck is driving to the tornado where the sensors spill, the scenery and pavement change between shots. First, they are driving down a road with trees on both sides. Then, they are driving down a large empty area where you can see the the horizon. Finally, they drive into a valley with forests on both sides. And this happens in a matter of seconds.
Continuity mistake: During the last tornado scene, one of the team members says "they're going to punch the core" as Bill and Joe turn right off the road towards the F5. If you look ahead of their truck above the cornfield there is no sign of the F5 they turned apparently towards.
Revealing mistake: At the start, while Jo and her parents are inside their storm cellar, Jo's father attempts to hold down the overhead cellar door during the tornado. Then, just as the F5 yanks the cellar door up along with Mr. Thornton, we can see the cable link that is attached between the actor's back and the cellar door, for this stunt. (00:04:20)
Other mistake: The order of action performed to activate Dorothy 2 (jumping tornado scene) and 4 (F5 tornado scene) is reversed. Also, Bill somehow has more switches to flip. Jo pressed a button, flipped a couple switches and then told Bill Dorothy was ready, while Bill had to flip the same switches, then flip some more, then press the buttons before starting to unstrap the device from the truck. (Jo didn't have to unstrap D4 because they realised at that point it had to be anchored to something heavy because the device was too light and decided to sacrifice the truck). However it is possible that Bill actually flipped the same switches twice. We can see him flip the switches, then we have a quick close shot of Dorothy 2 then the camera goes back to Bill flipping the switches again. There is no such angle change during the part where Jo activate D4, so it's very much probable that they got two angles of Bill Paxton flipping the switches, but forgot to cut one. (00:59:15 - 01:36:00)
Revealing mistake: During the scene when the repair shop is falling apart from the tornado, a wire can be seen pulling the drive in theater sign into the building in a brief shot.
Factual error: In the scene when Bill and Joe are about to deploy Dorothy 2, we see that the tornado (F-2 I believe) rips out an entire row of power poles high into the sky with the power lines still attached to the poles straight from the ground. In real life, when a tornado runs over power poles, it would only knock them down.
Continuity mistake: When Jo and Bill are traveling in the ditch during the tornado they show them hitting the bridge from the front and then they change the angle to the passenger side (Jo's side) and they show them hitting the bridge again.
Factual error: Near the beginning, when we see Bill and Jo in Jo's truck driving in an off-road ditch being "chased" by a tornado, there is a shot where we see the tornado dismantle a barn. In real life, you wouldn't be able to see it dismantle the barn board by board. The tornado would actually cover the barn, and when it leaves, you would see the barn in desolation.
Revealing mistake: In the opening scene, where Jo is very young and her dad and mom are carrying her and running from the house to enter the storm shelter, the tornado is just 60 seconds or so from destroying their house and sucking Jo's dad away. If you look at the trees behind them as they are running, you can see the trees are barely moving from any wind at all. If a real tornado was that close, the trees would be half bent over from the 60-100+ mph wind.
Continuity mistake: When they are driving in the Dodge Ram, the window gets shattered at one point, and then they literally drive through a house and then as they come out, the window is intact again.
Continuity mistake: When Bill and Jo are in the yellow pick-up going after the first tornado, there is a yellow raincoat with a visible metal snap hanging from a hook mounted on the rear window directly behind Jo. As the scene progresses, it moves to a position higher up and off the window when Jo says, "We're moving to intercept, guys. Get ready to set up." Then Bill gets off the road and down into the ditch, right before Bill says, "Are we having fun yet?" the raincoat is back hanging from the hook on the window behind Jo in a different position (no snap visible).
Continuity mistake: When Bill, Jo, and Bill's therapist fiancée are in Bill's red truck and about to be engulfed in the tornado where the cows are flying around, the fiancée's cell phone is ringing for about the fifth time in as many minutes. The fiancée answers the phone with a disgusted look on her face like she resents having to answer the phone during such a dangerous time. Obviously the call is deliberate 'comic relief', even though they were so close to the tornado and about to be engulfed, but the real problem is in reality she would not have been able to hear it ring amongst the grand noise of all the wind.
Continuity mistake: At the roadside restaurant, when Bill first sees Jonas' version of Dorothy, we see it from Bill's perspective. You can see that the panels in DOT's top are open. In the next shot, Jonas is discussing DOT with the press and the top is closed then opens as he describes the sensors. (00:20:25)
Other mistake: In the garage scene just as the neon sign collapses almost onto the storm chasers, the scene plays twice when the sign lands near the storm chasers who are taking shelter in the garage pit.
Continuity mistake: Towards the end of the film when they are preparing Dorothy 4, the twister behind them is about 5 metres away. Then it it much further back the next time we see it.
Continuity mistake: Near the beginning, when Bill and Melissa have gone to get the divorce papers, Bill leaves Melissa talking to Dusty. When Dusty starts telling her about the "suck zone" there are a couple of black cows behind Dusty. Next, Jo comes over to meet Melissa and when the camera pans to the same area behind Dusty, there are no cows. (00:12:50)
Continuity mistake: When Jo, Melissa and Bill are in his car, they see Jonas wave from his car. Just before this had happened, Jonas looked in his rear view mirror. He only saw a red car with a background of a paved street. Where is the rest of Jo and Bill's crew?
Other mistake: Less than a few minutes into the film, there is a shot of a dark sky looking through a barbed wire fence with yellow wildflowers at the bottom of the frame. The flowers start blowing in the wind, and then snap back to the beginning of the shot. Just before the shot cuts, the wildflowers move again, repeating the action earlier. The shot is looped.
Continuity mistake: Right before the tree gets stuck on the axle of the red truck, there is a shot of the car turning. The tires are already chewed up from the scene coming up where they try to take off.
Answer: Based on his scenes, he seems to be a photographer for the team. He was taking pictures of Jo, showing how Dorothy worked, and was setting up a camera when Bill and Jo were going after the F5 at the end.