HILDA

History

Tropical Cyclone Hilda originated from a shallow tropical low that formed along the monsoon trough over the central Coral Sea on 4 March 1990. Rather than moving away immediately, the developing system executed a tight clockwise loop near 20°S over the following two days. Favourable upper-level outflow allowed the low to consolidate quickly, and the Brisbane Tropical Cyclone Warning Centre named it Hilda as a Category 1 system on 5 March.

Intensification continued overnight, and Hilda reached Category 2 strength on the Australian scale early on 6 March while still over open Coral Sea waters, well away from land. At its peak the cyclone produced maximum 10-minute sustained winds of about 100 km/h, with gusts estimated near 140 km/h, and a minimum central pressure of roughly 984 hPa. Steered by mid-latitude flow at mid-levels, Hilda recurved from an easterly heading toward the south-southeast on 6–7 March, tracking past New Caledonia and passing approximately 280 km to that territory's southwest on 7 March.

As the cyclone pushed into higher latitudes it encountered stronger upper-level wind shear and progressively cooler sea surface temperatures. Hilda lost its tropical characteristics on 8 March near latitude 26°S, ending a tropical cyclone phase that had lasted only from 5 to 8 March. The resulting extratropical depression proved remarkably durable, retaining gale-force winds in its southern quadrant as it crossed the Tasman Sea, passed south of New Zealand's South Island, and finally merged with a high-latitude trough over the Southern Ocean around 19 March.

Hilda never made landfall and remained several hundred kilometres offshore from the Queensland coast for its entire tropical life. New Caledonia recorded squally winds and localised heavy rainfall on 7 March, and ships crossing the Tasman Sea reported gales, but no significant land-based damage, injuries or deaths were attributed to the system. Hilda was notable for its extraordinarily deep convection, with cloud tops estimated near 19,200 metres and a measured cloud-top temperature of −100 °C — at the time the coldest ever recorded, a mark that stood until Typhoon Kammuri in 2019.

Sources: Bureau of Meteorology report Wikipedia