relativistic forces

The formal analogy concerning velocity dependent forces in electrodynamics and gravity enables to identify the Coriolis-force \(2\vec{\Omega}\times\vec{\upsilon}\) and the Lorentz-force \(\vec{\upsilon}\times\vec{B}\). Where does the factor 2 come from? would there be an analogue of the centrifugal force which scales \(\propto \Omega^2\)?