Borneo vortices are cyclonic vortices that are weaker than tropical storm category and can bring heavy precipitation as they propagate across the South China Sea and surrounding countries. Here we investigate the climatology and structure of Borneo vortices as well and the link to cold surges and equatorial waves. In addition, we will investigate the structure and dynamics responsible for the intensification of a Borneo vortex that moved from the north of Borneo across the South China Sea and impacted Vietnam and Thailand in late October 2018. This case study is examined using Met Office Unified Model simulations and a semi-geotriptic balance approximation tool.