The domed cylindrical shape of the New Day shelter really makes it tough!  Like a commercial aircraft, this form causes the metal structure to be as strong as physically possible. Also like a plane, this shelter is slick in super-high winds.  We don't think much about stationary objects needing to be aerodynamic, but certainly a safe room should be when it is in winds approaching Mach 0.4!  (Its drag coefficient is just 0.63 producing near-zero lift!)