Area of effect is centered on an intersection (when on a grid)
The meteors target a point and then explode in a radius – they thus have an area of effect.
When using a tactical map with area of effect spells, you should select an intersection, not the center of a space.
Choose an intersection of squares or hexes as the point of origin of an area of effect, then follow its rules as normal. If an area of effect is circular and covers at least half a square, it affects that square.
Related: How do I target the Moonbeam spell, using a grid?