Extratropical

I've often wondered why a Tropical System (ie: Hurricane Maria) can suddenly become "Extratropical"...its bugged me so now I know and I know y'all are dying to know this too:

How tropical and extratropical systems differ:

Tropical system
Forms over a tropical ocean.
Center of storm is warmer than the surrounding air.
Has no fronts.
Strongest winds are near the Earth's surface.

Extratropical system
Forms outside the tropics.
Center of storm is colder than the surrounding air.
Has fronts.
Strongest winds in the upper atmosphere.