Abstract: A band-pass filter is used to separate synoptic systems from subsynoptic ones in the outer circulations of tropical cyclones, disclosing that the severe outer precipitation shows close relations of convergence with low-level synoptic scale systems. In the paper’s computation of exchanges of momentum and vorticity between the two systems, it is known that the transfer of momentum is langely from synoptic systems to subsynoptic ones for levels higher than 650 hPa and the opposite process takes place for levels lower than it, while the momentum moves from synoptic systems to subsynoptic ones in integrations for the full layer. In the exchange of vorticity, the direction is from subsynoptic systems to synoptic ones for levels between 900 and 400 hPa, i. e. consequently , subsynoptic systems get less cyclonic and synoptic ones more cyclonic. The direction is the opposite for levels below 900 hPa or above 400 hPa. Full layer integrations suggest transfers of positive vorticity from subsynoptic scale systems to synoptic ones.