Cyclone Monica - Meteorological History

Meteorological History

Severe Tropical Cyclone Monica originated from an area of low pressure that formed early on 16 April off the coast of Papua New Guinea. The low quickly became organised, with deep convection developing over the low-pressure centre. Later that day, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert as the system became increasingly organised. Early the next day, the Bureau of Meteorology in Brisbane, Australia declared that the low had developed into a Category 1 cyclone on the Australian tropical cyclone scale, with winds reaching 65 km/h (40 mph ). Upon being classified as a cyclone, the storm was given the name Monica. At the same time, the JWTC designated Monica as Tropical Cyclone 23P. Monica tracked generally westward, towards Far North Queensland, in response to a low to mid-level ridge to the south.

Low wind shear and good divergence in the path of the storm allowed for continued intensification as continued westward. Late on 17 April, Monica intensified into a Category 2 Cyclone, with winds reaching 95 km/h (60 mph ). By 1200 UTC on 18 April, the Bureau of Meteorology upgraded Monica to a severe tropical cyclone, a Category 3 on the Australian scale. This followed an increase in the storm's outflow and a fluctuating central dense overcast. Several hours later, the JTWC upgraded Monica to the equivalent of a Category 1 hurricane on the Saffir–Simpson Hurricane Scale. 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 (80 mph ). At the same time, the JTWC assessed Monica to have intensified into a Category 2 equivalent storm with winds of 155 km/h (100 mph ).

Shortly after making landfall, convection associated with the storm deteriorated and the outflow became fragmented. A shortwave trough to the south caused the ridge steering Monica to weaken, leading to the cyclone moving slower. After moving over land, the storm began to weaken, with the Bureau of Meteorology downgrading the storm to weaken to Category 1 cyclone and the JTWC downgraded the cyclone to a tropical storm. The following day, Monica moved offshore, entering the Gulf of Carpentaria. Once back over water, favourable atmospheric conditions allowed the storm to quickly intensify. Within 24-hours of moving over water, Monica re-attained severe tropical cyclone status. Following a shift in steering currents, the storm slowed significantly and turned north-westward. Steady intensification continued through 22 April as the storm remained in a region of low wind shear and favourable diffluence. Early on 22 April the Bureau of Meteorology upgraded Monica to a Category 5 severe tropical cyclone, the third of the season. By this time, a 37 km (23 mi) wide eye had developed within the central dense overcast of the cyclone. Later that day, the JTWC assessed Monica to have intensified into a Category 5 equivalent storm.

Cyclone Monica attained its peak intensity on 23 April near Cape Wessel with a barometric pressure 916 mbar (hPa; 27.05 inHg). Maximum winds were estimated at 250 km/h (155 mph ) by the Bureau of Meteorology while the JTWC assessed it to have attained winds of 285 km/h (180 mph ). Using the dvorak technique, the peak intensity of the cyclone was estimated over 320 km/h (200 mph) along with a minimum pressure below 869 mbar (hPa; 25.66 inHg). At its peak, Monica exceeded a T# of 8.0, the highest ranking on the Dvorak Scale. However, since the JTWC is not the official warning centre for Australian cyclones, these intensities remain unofficial.

On 24 April, the mid-level ridge south of Monica weakened, causing the storm to turn towards the south-west. 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 (155 mph ). Not long after making landfall, the storm weakened extremely quickly. Most convective activity associated with the storm dissipated within nine hours of moving onshore. This resulted in the storm's maximum winds decreasing by 155 km/h (100 mph) in a 12-hour span. After this rapid weakening, the storm turned sharply west moving over the town of Jabiru as a Category 2 cyclone. Within six hours of passing this town, the Bureau of Meteorology downgraded Monica to a tropical low, no longer producing gale-force winds. The JTWC issued their final advisory on the storm at 1800 UTC that day. 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. The remnants eventually dissipated on 28 April over central Australia.

The Bureau of Meteorology uses 10-minute sustained winds, while the Joint Typhoon Warning Center uses one-minute sustained winds. The Bureau of Meteorology's peak intensity for Monica was 250 km/h (155 mph) 10-minute sustained, or 285 km/h (180 mph) one-minute sustained. The JTWC's peak intensity for Monica was 285 km/h (180 mph) one-minute sustained, or 250 km/h (155 mph) 10-minute sustained.