Becky Britton & Kim Quach

1. How unnatural were the rainfall events caused by Cyclone Yasi, Feb 2011 in Innisfail, Queensland? Becky Britton & Kim Quach

2. Cyclone Yasi • Cyclone Yasi began as a tropical low to the northwest of Fiji, on the 29th January 2011 and began directing westward toward Australia • Cyclone Yasi hit the North-East coast of Queensland in the early morning of February 3rd 2011, where it also became a category 5 cyclone. Yasi Targeted many cities along the coast and slightly inland, Innisfail being one of the many. • The cyclone finally weakened at around 10:00PM near Mount Isa on the 3rd February 2011 . • Yasi is one of the most disastrous and powerful cyclones ever to have hit Queensland since records began, as evident in the astounding impact it made to Innisfail’s rainfall in early February 2011 • We have based our research on the information of http://www.bom.gov.au/climate/data/

3. Voronoi Graph Development • We decided to use the method of a Voronoi Graph, or Thiessen Polygon as referred to with climate, to display our research • We found a map of our region where the cyclone hit (Innisfail) to base our graph upon • All the nearest rainfall gauges to our region were located and connected to their nearest neighbouring gauges, forming triangular figures • We then identified the half way point of each line and drew a perpendicular line through • The perpendicular bisectors were constructed and joined to form our regions

4. Voronoi Graph Completed Russel River Daradgee Innisfail Mean of Feb 2011: 32.46ml Median of Feb 2011: 7.5ml Tung Oil Alert Nerada Alert Marco Street Alert Corsis Alert South Johnstone Exp Stn Central Mill TM

5. The horizontal blue lines across the graph display the mean and median rainfall measurements of the Innisfail Queensland water gauge from Jan 15 – Feb 15 2011 These graphs present the numerical values we gathered from www.bom.gov.au We can observe that Cyclone Yasi hit Innisfail around the time of Feb 3rd and 4th and we can see the unnatural impact it caused toward Innisfail’s rainfall levels. Mean Median

6. In the past 13 years, 2011, the year of Cyclone Yasi, holds the third highest level of February rainfall. Innisfail has also experienced such occasions before, as seen in 2007 and 2009.

7. This graph compares the total, mean and median rainfall of each month over the time period of 2000-2013. The total rainfall levels are the sum of all the measurements, the mean being the average and the median, the middle of the results. 2011 definitely stands out in terms of rainfall data. The levels of February and March towering over the means and medians of the past 13 years. Cyclone Yasi greatly affected Innisfail's rainfall.

8. Conclusion • From the statistics gathered, we can come to a decision that Cyclone Yasi had created a significant alter in the rainfall standards of Innisfail Queensland, February 2011 • In contrast to the days (slide 4), months (slide 5), and years (slide 6), Cyclone Yasi has greatly impacted the results, which is evident in the surges it has caused • From mid January - mid February 2011, the rainfall levels ranged from 0 – 193ml of rain. The 3rd of February 2011 being the highest peak, also a day within the time of Cyclone Yasi • Out of all the February’s of 2000 – 2013, the results ranging from 107 - 1134, February 2011, with 909ml of rain, having the third most level of rainfall. • And of the months of 2000 – 2013, the results range from 31 – 980ml. The second highest point of 909ml being February 2011, the month of Cyclone Yasi and the month of the second most highest level of rainfall out of the 156 months from 2000 – 2013 • Cyclone Yasi: highest rainfall of mid Januray – mid February 2011 (1st out of 30 days), third highest of all February’s of 2000 – 2013 (3rd out of 12) and the second highest rainfall of all months from 2000 – 2013 (2nd out of 156) Reference: Climate Data Online. 2013. Climate Data Online. [ONLINE] Available at: http://www.bom.gov.au/climate/data/. [Accessed 05 September 2013]