Depends how deep it is and the strength of the tornado. However, they are still better than nothing when you can't get to shelter.
hide in a ditch or low-lying area.
Find A ditch to hide in.
Find a deep ditch, lay in it.
Despite it being a funnel, you are less likely to be pulled into a tornado if you are below ground level. The wind tend to go over the ditch more than they go into it. Additionally, the ground around you can shield you from flying debris, the biggest danger in a tornado. Keep in mind, though that a ditch is only to be used as a last resort. If there is a sturdy building nearby go there instead.
If the tornado is still distant, drive perpendicular or diagonal to its path (depending on the roads) to get out of the way. If the tornado is getting close, abandon the car and get in a ditch as a last resort or, better yet, a nearby sturdy building.
If you cannot get to any safe shelter or even a ditch during a tornado, lie flat on the ground.
get in a ditch
To some degree. You should only take cover in a ditch from a tornado as a last resort if no shelter is available.
hide in a ditch or low-lying area.
try and get as low as you can. like in ditch
Find A ditch to hide in.
When you see a tornado, go into a secure building or if there are none near you, huddle in a nearby ditch.
If no shelter is available lie down in a ditch.
Find a deep ditch, lay in it.
Lie in a ditch or depression in the ground if you cannot get to shelter.
Lie down in a ditch or depression in the ground and cover your head.
If you are outside with no shelter a available and a tornado is coming the best option is to lie in a ditch or depression in the ground