I don’t know if this is below ground enough to be used as a storm shelter but this would be a beautiful root cellar! Check out Earthbag Building for how to build it.
“One of the most practical structures on a small farmstead is a multi-purpose garden structure that can serve as a storage shed or cool pantry above ground, or as a root cellar or storm shelter below ground. You can build this multipurpose structure for about $300 using earthbag construction (bags filled with earth and stacked like bricks). And the skills you learn by building the dome will serve you well if you plan to build a larger earthbag structure or even an earth home.”
via Earthbag Building: Low-Cost Multipurpose Minibuilding.