Here are two examples of phenomena that cannot be explained on a Flat Earth:

• the Coriolis Effect. Weather patterns (hurricanes, large storms etc) spin counterclockwise above the equator and clockwise below it. This is in good accordance with Earth's shape and rotation. On a flat Earth storms would spin in the same direction above and below the equator. This Coriolis doesn't have an influence only on weather. Even ballistic trajectories (the trajectories of bullets or long-range artillery shells) are affected by it and it must be taken into account when the said trajectory is calculated.
• the apparent rotation of stars. In the northern hemisphere, the stars in the night sky rotate around Polaris (the celestial north pole). In the southern hemisphere, the stars will rotate around Sigma Octantis (the celestial south pole).

Note: Sigma Octantis is very dim and difficult to see with the naked eye, therefore the Southern Cross is used for convenience.