This paper presents the electromagnetic topology selection and thermal analysis of a liquid-cooled high speed surface-mount permanent magnet electrical synchronous machine (SMPMSM), with a power density exceeding 30MW/m3 using thermal resistance networks. The parametric thermal models that have been developed cater for the axial temperature distribution in the machine while operating at speeds of up to 120,000 rpm. This is required due to the asymmetrical thermal boundary conditions imposed on the machine by the application environment causing a thermal gradient along the axis of the machine. Windage losses, which constitute a significant proportion of the total losses at the high speeds considered are estimated and nodes are placed in the air-gap so as to input this heat flux into the thermal resistance network.