Cyclone Nancy

Severe Tropical Cyclone Nancy

Category 4 severe tropical cyclone (Aus scale)
Category 4 (Saffir–Simpson scale)
Cyclone Nancy on February 15
Formed	February 10, 2005
Dissipated	February 17, 2005
Highest winds	10-minute sustained: 175 km/h (110 mph) 1-minute sustained: 230 km/h (145 mph)
Lowest pressure	935 hPa (mbar); 27.61 inHg
Fatalities	None reported
Areas affected	Cook Islands and American Samoa
Part of the 2004–05 South Pacific cyclone season

Cyclone Nancy (RSMC Nadi designation: 09F, JTWC designation: 18P) was the second in a series of four severe tropical cyclones to impact the Cook Islands during February 2005. Forming out of an area of low pressure on February 10, Nancy quickly organized into a small, but intense, cyclone. By February 14, the storm explosively intensified into a Category 4 severe tropical cyclone with winds peaking at 175 km/h (110 mph 10-minute winds) and a minimum barometric pressure of 935 hPa (mbar). Over the following day, increasing wind shear rapidly weakened the cyclone and by February 17, it transitioned into an extratropical cyclone shortly before being absorbed by Cyclone Olaf.

Already impacted by Cyclone Meena in early February, the Cook Islands sustained significant damage from Cyclone Nancy. Several homes were damaged and destroyed throughout the islands. Downed trees and power lines blocked roads and cut power and minor flooding was reported along coastal areas. Following the impact of the storm, the World Meteorological Organization retired the name Nancy in May 2006 and replaced it with the name Nat.

Cyclone Nancy originated out of a broad area of low pressure within a monsoonal trough northeast of Samoa on February 10. Initially, the system was nearly stationary within an area of weak steering currents, low wind shear and high sea surface temperatures, exceeding 30 °C (86 °F). On February 11, a trough briefly increased shear over the system and its nearby twin, the precursor to Cyclone Olaf. By 0600 UTC on February 12, the system's outflow improved and a small area of deep convection, known as the central dense overcast, developed over the center of circulation. Later that day, the Regional Specialized Meteorological Centre (RSMC) in Nadi, Fiji upgraded the system to a Category 1 cyclone and gave it the name Nancy while it was located about 485 km (300 mi) east-northeast of Pago Pago, American Samoa. By this time, the Joint Typhoon Warning Center (JTWC) had also begun issuing advisories on the storm, designating it as Tropical Cyclone 18P.