Atmosphere And Weather

Cyclone Yasi

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"Cyclone Yasi"
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On January 26th, 2011, the Fiji Meteorological Service identified a weak tropical disturbance in the south Pacific, about 200 miles to the south of the small island nation of Tuvalu.

At first, the weak system tracked very slowly to the west. Gradual intensification began to occur, and it was upgraded from an area of interest to a tropical depression by the next day.

Moving over warm waters with low wind shear allowed the developing storm to strengthen, and on January 30th, it was upgraded to a Cyclone as 10-minute sustained winds exceeded 40 mph. At that point, it was positioned about 230 miles north of the island of Vanuatu. The meteorological office in Fiji assigned it the name Yasi.

From there, Yasi began to intensify rapidly even further, and the next day it was upgraded further to a Category 2 Cyclone with winds greater than 55 mph. During that day, it impacted Torba, a northern province of Vanuatu with 60 mph winds, causing no major damage.

By 4 o’clock that same day, sustained winds had surpassed 74 mph, and it was thus designated as a Category 3 Severe Cyclone. This strength was maintained over the next 24 hours as Yasi began to pick up speed and make a turn to the west-southwest to aim towards Queensland, Australia.

Sustained winds exceeded 100 mph the evening of February 1st, and Yasi was upgraded to a Category 4 storm. However, it was not done intensifying yet, and by early on the morning of the 2nd, it topped the southern Pacific cyclone scale at Category 5 with 10-minute sustained winds of 125 mph.

On the American hurricane scale, which uses 1-minute sustained winds, Yasi would have been a strong Category 4 storm with 155 mph winds.

Later that day, Yasi swept over Willis Island, located about 280 miles to the east of Cairns, Queensland. Communication with the island was totally lost as barometric pressure dropped to 938 mb. The island’s anemometer was broken after recording a wind gust of 115 mph.

The cyclone finally reached Queensland around midnight on February 3rd, making landfall near a seaside town called Mission Beach. Pressure there dropped to 929 mb, and wind gusts were estimated to be as high as 180 mph.

This wind, combined with a storm surge as high as 23 feet resulted in significant damage to much of northern Queensland. Initial estimates put the cost of the damage at 3.5 billion Australian Dollars. However, despite all of this destruction, only one death was recorded: an asphyxiation due to carbon monoxide from a portable generator.

Though Yasi weakened significantly as it moved towards central Australia, it still brought significant rain to many locales. Rainfall amounts ranged from three to five inches in central Australia near the city of Alice Springs. This resulted in widespread flooding.

However, fortunately for residents of that region, this rainfall was very short-lived, and Yasi fully dissipated on February 6th after leaving a trail of destruction across Australia.

More about this author: Bradford Guay

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