After being named, Ivy quickly intensified after its convection was drawn into the circulation. Late on February 23, the JTWC upgraded Ivy to the equivalent of a Category 1 hurricane on the Saffir-Simpson scale, and the FMS followed suit the following day by upgrading Ivy to a severe tropical cyclone as continued favorable conditions allowed for rapid deepening. On February 24 the cyclone began a turn to the southwest as it moved around the ridge, and the next day it turned to the south toward Vanuatu as an approaching shortwave trough passed to the south and created a weakness in the ridge. A nearby upper-level low temporarily cut off outflow, although once it moved further away the low enhanced ventilation. Strengthening continued and, late on February 25, the FMS reported that Ivy attained peak 10–minute sustained winds of 165 km/h (105 mph) over the Vanuatu archipelago; this made it a Category 4 on the Australian Region Tropical Cyclone Intensity Scale. Around the same time, the JTWC estimated peak 1–minute sustained winds of 195 km/h (120 mph), after a 19 km (12 mi) eye developed.