How unnatural were the rainfall events caused by Cyclone Yasi,

Feb 2011 in Innisfail, Queensland?Becky Britton & Kim Quach

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/

Cyclone Yasi

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

Daradgee

InnisfailMean of Feb 2011: 32.46mlMedian of Feb 2011: 7.5ml

South Johnstone Exp StnCentral Mill

TM

Marco Street Alert

Tung Oil Alert

Russel River

Nerada Alert

Corsis Alert

Voronoi Graph Completed

Jan 15

th

Jan 17

th

Jan 19

th

Jan 21

st

Jan 23

rd

Jan 25

th

Jan 27

th

Jan 29

th

Jan 31

st

Feb 2n

d

Feb 4t

h

Feb 6t

h

Feb 8t

h

Feb 10

th

Feb 12

th

Feb 14

th0

40

80

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Jan 15 – Feb 15 2011, Inn-isfail QLD

Daily Rainfall

Mill

ilitre

s

Mean

Median

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 2011We 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.

These graphs present the numerical values we gathered from www.bom.gov.au

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

0200400600800

10001200

February Rainfalls, Innisfail QLD

February Total

Mill

ilitre

s

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.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0100200300400500600700800900

1000

Monthly Rainfalls, Innisfail QLD

Monthly Total 2011 Mean 2000-2013Median 2000-2013

Mill

ilitre

s

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.

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]