Cyclone Olaf - Meteorological History

Meteorological History

A tropical wave formed on February 10. The tropical wave, then spawned two areas of low pressure, one of which became Tropical Depression 08F. At 1300 UTC, the tropical depression was located 490 miles north west of Apia. By 1500, the depression organized into a tropical storm with 40 mph wind and was named Olaf. At the time of formation, the tropical storm was nearly stationary. The low wind shear and warm water temperatures allowed Olaf to undergo rapid intensification. In a 12 hour period, Olaf quickly became a Category 1 cyclone with 80 mph (130 km/h) winds in a 10 minute average speed. On February 15, the barometric pressure fell to 930 mbar as Olaf reached Category 4 status. After reaching Category 4 status, Olaf then moved on a south-southeasterly course at 7 mph (11 km/h).

Cyclone Olaf then tuned east and moving 100 miles (165 km) east of Western Samoa. On February 16, satellite imagery depicted a well-defined eye as Olaf strengthened into a Category 5 cyclone. Olaf reached a peak intensity of 165 mph with a barometric pressure of 915 millibars. It is possible Olaf could have a lower pressure but official track reports have Olaf at 915 mbar. At the time of peak intensity, the center of the storm was only 70 miles (120 km) northeast of American Samoa and 90 miles (145 km) northwest of Pago Pago. At the same time, Cyclone Olaf underwent a minor Fujiwhara effect with Cyclone Nancy before resuming its southeasterly course. Moving at 10 mph (16 km/h), the cyclone maintained Category 5 status as the eye passed 15 miles east of Ta'u, American Samoa. During that time, a weather station reported a 931 barometric pressure reading.

On February 18, an approaching upper level trough to the south, and strong wind shear caused Olaf to weaken as the storm rapidly moved southeastward. As Olaf moved into the New Zealand area of responsibility, the main circulation separated from the center and Olaf quickly became extratropical 18 hours later. The extratropical remnants of Olaf, quickly re-intensified into a powerful extratropical storm on February 23. The extratropical storm persisted for two days before dissipating near Pitcairn Island