Cyclone Ivan - Meteorological History

Meteorological History

On February 5, an area of convection persisted about 555 km (900 mi) north of Réunion in the southwest Indian Ocean. The system maintained a broad low-level circulation with associated deep convection, and it slowly developed banding features. By early on February 7, the circulation had become better defined as it remained in an area of weak wind shear and strong diffluence. At 0600 UTC, Météo-France (MFR) classified it as Tropical Depression Eleven about 880 km (550 mi) north-northeast of Mauritus. Around the same time, the Joint Typhoon Warning Center (JTWC) began issuing advisories on the system as Tropical Cyclone 18S. The depression tracked east-southeastward, under the influence of a mid-level ridge. A cutoff low to the south of the system enhanced upper-level conditions, and it quickly strengthened into Tropical Storm Ivan.

The storm rapidly organized and developed an eye feature. Its intensification rate slowed as an upper-level trough began restricting outflow, and the motion of Ivan became nearly stationary as it entered an area of weak steering currents. With its overall environment remaining favourable, the JTWC upgraded Ivan to tropical cyclone status – winds greater than 119 km/h (74 mph) – early on February 9. However, the MFR retained Ivan as a strong tropical storm. Late on February 9, the storm temporarily weakened when wind shear increased, though the next day it re-intensified as convection increased; a banding eye formed in the center of the convection, prompting the JTWC to re-upgrade Ivan to tropical cyclone status late on February 10. On February 11, the MFR upgraded Ivan to tropical cyclone status 1025 km (640 mi) northeast of Mauritus.

By February 14, it had sped up and entered a more favourable environment, becoming a severe tropical storm. On February 15, Ivan was re-upgraded to a tropical cyclone as favourable conditions persisted. Ivan was further upgraded to an Intense Tropical Cyclone on February 16 as it moved closer to Madagascar. Ivan made landfall north of Fanoarivo, Madagascar on February 17. Once overland, rapid weakening occurred due to the rugged terrain of the island. Ivan was forecast to regenerate over the Mozambique Channel into a tropical depression once it left Madagascar. Ivan traversed Madagascar, heading southwest. Its remnants emerged back over water on February 21, and Météo-France resumed advisories on "filling depression Ex-Ivan". Ivan, severely disrupted by Madagascar, did not strengthen any further; the last advisory was issued on February 22.