Evidence from recent satellite observations and results from the Coupled Hurricane Intensity Prediction System (CHIPS) coupled typhoon-ocean model show that Maemi, the supertyphoon which devastated the southern Korean Peninsula in September 2003, was intensified by a prominent warm oceanic eddy. When passing over the eddy-rich zone near 22¢XN in the Northwest Pacific Ocean, Maemi encountered an intense warm oceanic eddy characterised by a high sea surface height anomaly of more than 35 cm, as observed by the TOPEX/Poseidon satellite altimetry sensor. Within 24 hours, Maemi's intensity (in 1-min. sustained wind) jumped from category-2 46 m s-1 to super category-5 strength of 77 m s-1. When running the hindcast CHIPS model without the incorporation of the eddy information, Maemi's intensity was underestimated by 40%. With the addition of the TOPEX/Poseidon altimetry sea surface height anomaly, CHIPS produces intensity close to the observed best track from the JTWC. These results highlight the role of warm oceanic eddies in tropical cyclone intensification.