The 17th and final storm of the 2005–06 Australian region cyclone season, Monica originated from an area of low pressure off the coast of Papua New Guinea on 16 April 2006.

Travelling towards the west, the storm intensified into a severe tropical cyclone before making landfall in Far North Queensland, near Lockhart River, on 19 April 2006.

Early on 22 April 2006, the Bureau of Meteorology (BoM) assessed Monica to have attained Category 5 status, on the Australian cyclone intensity scale.

Severe Tropical Cyclone Monica originated from an area of low pressure that formed early on 16 April 2006 off the coast of Papua New Guinea.

Later that day, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert as the system became increasingly organised.

[1][3] By 1200 UTC on 18 April, the Bureau of Meteorology upgraded Monica to a severe tropical cyclone, a Category 3 on the Australian scale.

[4] During the afternoon of 19 April, the storm made landfall roughly 40 km (25 mi) south-southeast of the Lockhart River with winds of 130 km/h (81 mph) 10-minute sustained).

A shortwave trough to the south caused the ridge steering Monica to weaken, leading to the cyclone moving slower.

[1][9] Steady intensification continued through 22 April as the storm remained in a region of low wind shear and favourable diffluence.

[4] Cyclone Monica attained its peak intensity on 23 April near Cape Wessel with a barometric pressure 916 hPa (mbar; 27.05 inHg).

[11] Following this, the storm made landfall in the Northern Territory, roughly 35 km (22 mi) west of Maningrida, as a Category 5 cyclone with winds of 250 km/h (160 mph) 10-minute sustained).

Within six hours of passing this town, the Bureau of Meteorology downgraded Monica to a tropical low, as the storm was no longer producing gale-force winds.

[15] The remnants of Monica persisted for several more days, tracking near Darwin on 25 April before turning south-east and accelerating over the Northern Territory.

[4][17] While the storm was active the Bureau of Meteorology's Darwin Tropical Cyclone Warning Centre estimated that Monica, had peaked with a minimum pressure of 905 hPa (26.72 inHg).

[18][19] However, during their post analysis of Monica, the Darwin Tropical Cyclone Warning Centre estimated using the Love-Murphy pressure-wind relationship, that the system had a minimum pressure of 916 hPa (27.05 inHg).

[19][20] However, since then the BoM has started to use the Knaff, Zehr and Courtney pressure-wind relationship, which has estimated that Monica had a minimum pressure of 905 hPa (26.72 inHg).

[19] Upon being declared as Tropical Cyclone Monica on 17 April, the Bureau of Meteorology issued a gale warning for areas along the eastern coast of Far North Queensland and for northern New South Wales.

The chief executive officer of the community stated that they were ready for the storm, having suffered no losses from Cyclone Ingrid which impacted the same area in 2005.

[29][30] Alcan, the world's second-largest aluminium producer, warned customers of potential interruptions to supplies on contracts from its Gove refinery.

[37] Although the storm made landfall at peak intensity in Australia's Northern Territory, the impacted areas were sparsely populated.

[41] The remnants of Monica produced significant rainfall over parts of the Northern Territory several days after the system weakened below cyclone status.

[1] On 26 April, the remnants of Monica spawned a small tornado near Channel Point; several mangrove trees were snapped and branches were thrown to nearby beaches.

[42] The full-force of Monica's estimated 360 km/h (220 mph) wind gusts were felt in the unpopulated tropical savanna regions of northern Australia.

A large-scale windthrow event affected approximately 10,400 km2 (4,000 sq mi) of forest, resulting in the damage or destruction of 140 million trees.

The prolific loss of trees led to hydrologic changes in the region, with flood events likely becoming more severe as groundwater flow increased.

[38] Farther southwest, the Magela Creek catchment in Kakadu National Park suffered a direct hit from the weakening cyclone.

[43][38] With Monica occurring just before the onset of the dry season, widespread brushfires were anticipated in the affected regions owing to the large amount of kindling.

[43] Within weeks of the storm, the Alligator Rivers Region Advisory Committee began planting seedlings in deforested areas.

[44] Additional studies at the Gulungul Creek and the Alligator Rivers region revealed that suspended sediment values in flowing water had temporarily increased in the wake of Monica.