Lably
Skip to content

Cyclone Debbie

Category 4 Australian region cyclone in 2017

  • 8 min read
  • 4 chapters

Related on Lably

Through Australia

Meteorological history

On 22 March 2017, a well-defined but weak area of low pressure developed over the Coral Sea, near the Louisiade Archipelago of Papua New Guinea. Strong wind shear aloft kept the accompanying convection poorly organised and displaced west of the surface circulation. With environmental conditions forecast to improve and favour cyclogenesis, the Australian Bureau of Meteorology's (BOM) Tropical Cyclone Warning Centre in Brisbane classified the system as a tropical low on 23 March. Throughout the following day, decreasing shear enabled convection to wrap around the low; however, convective activity remained largely transient. A mid-level ridge to the east and an approaching trough over the Tasman Sea steered the low generally south. High sea surface temperatures of 29–30 °C (84–86 °F) and excellent dual-channel outflow fuelled rapid consolidation on 24 March. This prompted the United States-based Joint Typhoon Warning Center (JTWC) to issue a Tropical Cyclone Formation Alert, indicating the system was likely to acquire gale-force winds within 24 hours.

A scatterometer pass at 11:56 UTC revealed surface winds of up to 75 km/h (47 mph) and subsequent satellite intensity estimates supported gale-intensity, and the JTWC accordingly classified the system as Tropical Cyclone 13P by 21:00 UTC. With exceptionally favourable environmental conditions ahead of the storm, the agency noted a high probability for rapid deepening before landfall in Queensland. The BOM followed suit soon thereafter, classifying the system as a Category 1 tropical cyclone on the Australian cyclone intensity scale at 00:00 UTC on 25 March. Concurrently, they assigned it the name Debbie.

The cyclone continued to track generally southwards, developing into a Category 2 cyclone later that day. After attaining that strength, Debbie assumed a generally southwestwards track—a track it would maintain, with minor fluctuations, until about 14 hours after landfall. After a day-long period of arrested development, environmental conditions became highly favourable for renewed intensification. Beginning early on 27 March, Debbie strengthened rapidly from Category 2 to a Category 4 severe tropical cyclone in just 12 hours, and achieving peak sustained winds of 175 km/h (109 mph) and a minimum pressure of 949 hPa (28.02 inHg). After that, the Dvorak intensity given that the storm weakened slightly. Debbie passed over the Whitsunday Islands in the morning of 28 March local time with winds of 165 km/h (103 mph), still at Category 4 intensity. Nonetheless, the cyclone weakened to Category 3 before making landfall in Airlie Beach at 02:40 UTC with winds of 150 km/h (93 mph).

Following landfall, Debbie began to weaken steadily while interacting with North Queensland's rugged terrain. The cyclone weakened below severe tropical cyclone status while passing Collinsville at 12:00 UTC on 28 March. The system was downgraded to Category 1 in the early hours of 29 March local time, and then weakened further to a tropical low six few hours afterwards. The tropical low then executed a long turn to the southeast, and proceeded towards South East Queensland, moving roughly parallel to the coast. The remnants of Debbie brought heavy rainfall—torrential rains in many areas—that resulted in flooding in large parts of the land areas across which it tracked, before moving out over the Pacific Ocean on Friday 31 March.

Sign in to keep reading

3 more chapters are free with a Lably account.

More in Earth science