Just after the storm’s naming Pam, it began to curve southwards around midday on March 9. Computer models continued to point towards the possibility of rapid intensification occurring as the cyclone approached Vanuatu. Significant improvement in Pam’s organization took place throughout the remainder of the day into March 10. The cyclone’s circulation center quickly tightened, with the central dense overcast atop it persisting in strength. At 18:00 UTC on March 10, the FMS upgraded the system to category 3 strength, making it a severe tropical cyclone. Shortly after, microwave imagery revealed a primordial eye-feature developing within Pam; this became apparent on visible light images on March 11. That day, Pam became quasi-stationary east of the Santa Cruz Islands before resuming its prior motion towards the end of March 11. Favorable conditions allowed the cyclone to gradually intensify and attain Category 5 status on both the Australian and Saffir–Simpson scales on 12 March. Early on 13 March, the cyclone attained its peak intensity, with one-minute sustained winds of 270 km/hr (165 mph), 10-minute sustained winds of 250 km/hr (155 mph), and a central pressure of 899 hPa. Later that day, the Joint Typhoon Warning Center assessed the cyclone as having slightly weakened, with maximum one-minute sustained winds of 260 km/hr (160 mph); but, RSMC Nadi maintained that the cyclone was still at peak intensity.