Tropical Cyclone Gretel

Track map of tropical cyclone Gretel, image from
Track map of tropical cyclone Gretel, image from

Tropical cyclone Gretel formed on March 15 2020 in the Coral Sea to the West of Noumea. Gretel moved in a consistent south-eastward track across the Coral Sea region, from northern tropical coast of Australia to Norfolk Island, passing close to the south of New Caledonia as a category 2 cyclone. Gretel caused abnormally high tides and large surf about the southeast Queensland and northern New South Wales coasts. The centre passed to the northeast of Norfolk Island with marginal gales for a short period of time.

The tropical low that became Gretel was first identified and tracked from the northern Gulf of Carpentaria across the Cape York Peninsula to the northwest Coral Sea. The tropical low was part of a series of low-pressure systems embedded along a sharp elongated monsoon trough-oriented northwest to southeast, almost paralleling the Queensland coast. Gales were located well away from the low centre and on either side of the monsoon trough from 13 March due to a strong high located over the southern Australia and a strengthening northwest monsoon extending across the Cape York Peninsula.

The low tracked in a south-eastward's direction and was expected to develop into a tropical cyclone overnight on 13 March. But it wasn't until overnight on 14 March when monsoonal circulations around multiple low centres merged into a consolidated circulation. Gales were wrapping three quarters of the way around the centre and Gretel was named at 15Z on 14 march. The cyclone began to accelerate towards the southeast and intensified to a category 2 cyclone in the next 12 to 18 hours. Low shear environment with good upper level outflows to the north and south assisted this development. Gretel crossed the 160E longitude (Eastern Region boundary), passing close to the south of New Caledonia during 15 March.

The system moved past Norfolk Island on 16 March. As Gretel moved south of Fiji's area of responsibility (25S Latitude), it began to undergo extra-tropical transition and maintained its intensity as a category 2 system.