Cyclone Percy - Meteorological History

Meteorological History

On February 23, the Fiji Meteorological Service's Regional Specialised Meteorological Centre in Nadi reported that Tropical Disturbance 10F, had developed within the monsoon trough about 700 kilometres (430 mi) to the west of the Tuvaluan atoll: Funafuti.

10F was first identified as a tropical disturbance embedded in an active monsoon trough at 23/0000 UTC, approximately 380 miles to the west of Funafuti and moving eastwards about 05 to 10 knots. The system was then located just south of a 250-hPa ridge axis, in a diffluent region. Shear and diurnal variations were evidently influencing development. SST was around 31°C. Later on the 24th, shear had decreased markedly. Outflow was favourable and developing in all quadrants. Overnight, the depression underwent explosive development with the deep convection increasing spatially and in organization whilst cooling. Spiral bands were also wrapping tightly around the llcc. By 24/1800 UTC, TD10F was named Tropical Cyclone Percy, while located roughly 100 miles to the east of Funafuti and moving east-southeast at 14 knots under a deep west-northwest steering flow.

A discernible area of low pressure formed east of Tuvalu on February 23. The area of low pressure moved eastward, where it strengthened into Tropical Depression 10F a day later. Since the depression was located in an area of low wind shear and warm water temperatures, it was able to quickly strengthen into Tropical Storm Percy. At this point in time, Percy was located 120 miles (190 km) east of Fongafale, Tuvalu, and was moving towards the east-southeast at 14 kt (16 mph, 26 km/h). On February 26, Percy reached Category 1 status, while located 400 miles (644 km) north of American Samoa. While Percy moved east-southeast, a shortwave trough developed southwest of the storm. The trough caused the cyclone to intensify even further to a Category 3 storm as it passed between Fakaofa and Swains Island. Percy then reached Category 4 status north of Pago Pago as it winds reached over 135 mph (115 knots, 213 km/h) and the barometric pressure at its center fell to 925 millibars. On February 27, Cyclone Percy encountered a high pressure ridge which slowed its forward speed. Because of this, the cyclone's structure became elliptical, which caused the cyclone to weaken back to Category 3 status. By February 28, Percy bypassed the Pukapuka and Nassau Islands as a Category 3 cyclone as it continued to move east-southeast.

By then, the cyclone was re-organizing as the storm steered to the southeast. On March 2, Percy reached its second peak intensity. Its winds reached 160 mph (140 knots, 265 km/h) on the Saffir-Simpson Hurricane Scale, and an estimated barometric pressure of 900 millibars. Cyclone Percy maintained Category 5 status for 18 hours, while located 110 mi (177 km) west of Palmerston Island. After reaching Category 5 status, Percy began to weaken, due to increasing wind shear. During its weakening phase, Cyclone Percy passed south of Tropical Depression 20S. Pulled by an upper level trough, Percy swung to the east, passing Tropical Depression 24S in the process, before being caught up by another trough. By March 4, the center of Percy became detached from the main area of convection and Percy quickly weakened to a tropical storm. Tropical Storm Percy then quickly accelerated to 20 kt (23 mph, 37 km/h) as it became an extratropical storm.

Percy briefly entered the New Zealand area of responsibility before becoming extratropical at 1200 UTC. By March 5, the remnants of Percy finally dissipated 700 mi (1127 km) southwest of Rarotonga.