Summary

Severe Tropical Cyclone Yasi began developing as a tropical low northwest of Fiji on 29th January and started tracking on a general westward track. The system quickly intensified to a cyclone category to the north of Vanuatu and was named Yasi at 10pm on the 30th by Fiji Meteorological Service. Yasi maintained a westward track and rapidly intensified to a Category 2 by 10am on 31st January and then further to a Category 3 by 4pm on the same day.

Yasi maintained Category 3 intensity for the next 24 hours before being upgraded to a Category 4 at 7pm on 1st February. During this time, Yasi started to take a more west-southwestward movement and began to accelerate towards the tropical Queensland coast.

Yasi showed signs of further intensification and at 4am on 2nd February and was upgraded to a marginal Category 5 system. Yasi maintained this intensity and its west-southwest movement, making landfall on the southern tropical coast near Mission Beach between midnight and 1am early on Thursday 3rd February. Being such a strong and large system, Yasi maintained a strong core with damaging winds and heavy rain, tracking westwards across northern Queensland and finally weakened to a tropical low near Mount Isa around 10pm on 3rd February.

Yasi is one of the most powerful cyclones to have affected Queensland since records commenced. Previous cyclones of a comparable measured intensity include the 1899 cyclone Mahina in Princess Charlotte Bay, and the two cyclones of 1918 at Mackay (January) and Innisfail (March).

Wind Damage

At the time of writing there are no verified observations of the maximum wind gusts near the cyclone centre. However a barograph at the Tully Sugar Mill recorded a minimum pressure of 929 hPa as the eye passed over suggesting wind gusts of about 285 km/h were possible. This is supported by measurements (subject to verification) from instrumentation operated by the Queensland Government (Department of Environment and Resource Management) at Clump Point (near Mission Beach) which recorded a minimum pressure of 930hPa. Significant wind damage was reported between Innisfail and Townsville where the destructive core of the cyclone crossed the coast. Tully and Cardwell suffered major damage to structures and vegetation with the eye of the cyclone passing over Dunk Island and Tully around midnight on 2nd February.

The largest rainfall totals were near and to the south of the cyclone and were generally in the order of 200-300mm in the 24 hours to 9am Thursday. These rainfall totals were experienced in the area between Cairns and Ayr, causing some flooding. The highest totals were; South Mission Beach 471mm, Hawkins Creek 464mm, Zattas 407mm, Bulgun Creek 373mm along the Tully and Herbert River catchments.

In a time series of imagery from NASA’s Aqua satellite, the Atmospheric Infrared Sounder (AIRS) instrument showed Tropical Storm Aere’s progress over the weekend on May 6 at 16:59 UTC, May 7 at 05:29 UTC, and Monday, May 9 at 05:17 UTC. Infrared data basically takes the temperature of a tropical cyclone’s clouds and the coldest areas indicate the strongest thunderstorms and areas of heaviest rainfall. Those coldest cloud temperatures (highest, strongest thunderstorms) and are as cold as or colder than -63F/-52C.

On May 6, when Aere was a tropical depression (03W) it appeared to be more concentrated with the heaviest rainfall and strongest thunderstorms over open ocean. By Saturday, May 7, those heavy rains overspread land areas. On Monday, May 9, the circulation seemed to become weaker and convection seemed to appear more scattered and has decreased in AIRS imagery.

Warnings are still in effect in the Philippines as Aere continues to move north. Public storm warning signal #1 is in effect in the following provinces: Luzon: Quirino, Ifugao, Mt. Province, Kalinga, Apayao and Batanes. Public storm warning signal #2 is in effect for: Luzon: Cagayan, Babuya and Calayan.

The four fatalities caused by Tropical Storm Aere occurred in Balatan, Camarines Sur where a landslide took three lives, and another person drowned in floodwaters in Leyte. Radio reports also noted that nine people at the Manila airport were injured when lightning struck a plane on the tarmac on May 7.