Summary
A broad doldrum trough had been lying across the Coral Sea from Vanuatu to north Queensland for several days when a weak circulation became evident south of the Solomon Islands on 9 March 1980. The tropical depression drifted southeast then southwest slowly deepening for almost three days before reaching tropical cyclone intensity at 1800 UTC 11 March 1980.
Just four hours after becoming a cyclone Sina moved from the eastern Australian to the Fiji area of responsibility on a southeast track. It moved slowly at first and continued to intensify. Sina was a severe cyclone as it passed some 200 km to the southwest of New Caledonia.
After reaching peak intensity at 0200 UTC 13 March 1980, when the central pressure was 980 hPa, tropical cyclone Sina accelerated to over 30 km/h while maintaining a southeasterly track. It only very gradually weakened and was still generating storm force winds when it reached the north of New Zealand as an extratropical cold-cored depression on 15 March 1980.
Track and intensity
