You have to decide where your comfort level is with the odds. An F4 or F5 and that shelter won't survive. Anything less and you will probably be fine. Odds of an F4 or F5 are pretty small. Just depends on how you want to play it. Weigh the cost versus a buried shelter.
Yes, folks may know where to find you. But they may be out of town, injured or extremely busy. Give some thought to what you would do if the door was jammed. Don't count on any internet connections or anything requiring grid voltage. And your cell phone may not get much (if any) signal in there.
Study the FEMA Link Sir! my construction plans, according to FEMA will be good for F5 Tornadoes.
And door blockage may happen, that's why storm shelter door swing inside, not out.
I have already covered the fact that we will have several radios and 4G. All powered by solar recharged batteries that should be good for a week even if we lose it's solar panels. (I am already running a 12 volt solar freezer by solar power exclusively with this system, so I've crossed that bridge already.) Plus I highly doubt all my family, friends and neighbors, plus the entire National Weather Service will be on vacation at the same time a tornado wipes out my home, and no one comes looking for survivors in the damage area.
All of my neighbor, who have buried shelters, ALL have water issues in them. They are constantly having to replace sump pumps. Even my next door neighbors shelter in his closet, (a very large, and deep, one piece, fiberglass bathtub/ hot tub style in ground under a floor hatch) shelter fills with ground water on dry days. So where I live, underground is not a good option. Unless I want to deal with constant attention and diving into a half filled rancid pool of water. Your area is most likely different than mine! Consider storing your firearms in a damp cellar and get back to us on how that works for you!
Like you said, my design works for us! And I have spelled our out to help for those who want to plan theirs with ideas.
Anyone have any new products or ideas that might be useful in my situation?