The circulation which developed into tropical cyclone Blanch was first identified on 21 May 1987 some 800 kilometres east of Honiara. This system moved quickly west-southwest and slowly deepened until it crossed the southern tip of San Christobal Island in the Solomon Island group at 0000 UTC 22 May.
The next six hours saw rapid deepening until the system reached cyclonic intensity when near 11°S, 161°E with a central pressure of 998 hPa. Tropical cyclone Blanch then took on a southwesterly track, crossed Rennell Island around 1000 UTC 22 May and then slowed down. It continued to deepen and reached its lowest pressure of 990 hPa around 1800 UTC 22 May. This was maintained until 0000 UTC 24 May when it was near 15°S, 158°E.
The cyclone then began weakening whilst moving rather slowly first southwest then south-southeast and finally southwest again. It weakened below cyclonic intensity around 1800 UTC 25 May when near 17.S°S, 156.5°E. The resulting low was identifiable for a further 30 hours during which time the speed gradually increased and the track gradually turned from southwest to southeast. The system dissipated near 20°S, 157°E.
The lowest reported pressure was 1002.6 hPa at 0600 UTC 22 May at Kira Kira on San Christobal Island. The highest reported wind speed was 111 km/h also at Kira Kira but at 1200 UTC 22 May.
Other than contributing to the production of strong winds along the Queensland coast, this system had no effect on the Australian mainland. Some minor damage occurred in the Solomon Island group but no injuries were reported.