ΔE 15.9, loose: different enough that you should pick on purpose. Midnight Ink is a little darker, more saturated, warmer than Thunder Storm. They are different kinds of paint: Army Painter Thunder Storm is an opaque base/layer paint and Nocturna Models Midnight Ink is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Midnight Ink is a little darker, more saturated, warmer than Thunder Storm. They are different kinds of paint.
The same difference applies the other way round: Thunder Storm is a little lighter, more muted, cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Thunder Storm on the colour wheel See Midnight Ink on the colour wheel
All matches: Thunder Storm equivalents · Midnight Ink equivalents