Housing standards range from 26 lbs/sf to 400 lbs/sq ft depending on wind speed from 80 to 250 mph.
Assuming we can apply to these numbers to a 25' x 8' trailer, that's a lot of uplift - 5200 to 80000 lbs.
Clearly, the latter would simply destroy the trailer and/or frame, regardless of hold downs - so no parking that Airstream in the path of an F5
Obviously, the lower load limit is handled by the trailer weight.... so hold downs would help, but not in all cases. You're going to find installing big enough hold downs to be useful a real PITA, esp. in loose soil.
Personally, I'd be more worried about a tree falling on my trailer than getting carried away by a tornado.