Thursday, April 10, 2014

Severe Tropical Cyclone Ita to Produce Massive Storm Surge near World's Highest Historical Surge Site

Severe Tropical Cyclone Ita is bearing down on the Queensland Coast today. The storm is currently a category-5 tropical cyclone, according to Australia's Bureau of Meteorology. According to the 10PM (Australia Eastern Standard Time) advisory, Ita was packing wind gusts of approximately 285 km/hr (177MPH). These gusts would be well over category-5 intensity on the Saffir-Simpson Hurricane Wind Scale used in the United States, however, the Saffir-Simpson Scale categorizes according to sustained wind speed, so Ita would also be a major hurricane in the Western North Atlantic.

Satellite image of Tropical Cyclone Ita. Source: Australia Bureau of Meteorology

Ita will likely produce a large storm surge north of Cairns, with the highest levels likely north of Cape Flattery. Interestingly, the peak surge will likely be located just south of the location of Severe Tropical Cyclone Mahina's massive storm surge in 1899. Although scientific sources disagree about the details of Mahina's surge, many sources indicate that Mahina generated a 13.7-m (45 ft) storm tide near Bathurst Bay, Queensland. This water level ties Mahina with a Bangladesh surge in 1876 for the highest credible storm surge observation in the scientific literature. In short, Severe Tropical Cyclone Ita will likely produce a massive storm surge near the world's highest (tied for highest) historical storm surge site.

For the record, TC Mahina was more intense, with a lower central pressure than TC Ita. Mahina's central pressure was 915 hPa, which was the lowest on Australia's East Coast (Granger and Smith 1995), while TC Ita has a minimum central pressure of 934 hPa. Still, expect very strong winds and high surge with TC Ita.

Forecast track of Severe Tropical Cyclone Ita. The storm is forecast to strike the northern Queensland coast, north of Cooktown. Peak surge levels will likely occur north of Cape Flattery.

The Storm Surge Database (SURGEDAT) has now identified the location and height of peak storm surge for more than 700 global storm surges since 1880.  Australia and Oceania contain 134 observations in this dataset, including 69 observations from Queensland. TC Mahina (1899) is the largest surge observation in this region.

SURGEDAT contains a comprehensive dataset for Queensland from 1934-2011, with a limited amount of missing data. In that time frame, Queensland observed 31 surges > 1m, 14 surges > 2 m, 8 surges > 3m, and 3 surges > 5m. This means that per decade, Queensland averages 5.4 surges > 1 m, 2.5 surges > 2 m, 1.4 surges > 3 m, and 0.5 surges > 5 m. These statistics place Queensland, Australia as the fifth most active region in the world for tropical cyclone storm surges, according to the latest data from SURGEDAT.

The last surge in Queensland to exceed 5 m was the 5.33 m surge that was measured at the tide gauge in Cardwell, Australia, during Tropical Cyclone Yasi in 2011. Data Source:

TC Ita threatens to produce a large coastal flooding event north of Cairns, with highest water levels likely near and to the north of Cape Flattery. Stay tuned to the Australia Bureau of Meteorology and your favorite media outlets for updates on this dangerous storm.


  1. Hi Hal, it'll be interesting to see how high the actual peak surge will be. Our latest model predictions show a peak surge of 'only' 1.5 m. However, the resolution of the model that we used in this case was quite coarse (~5km), and it's quite possible that this leads to underestimation in places.

    An animation of our forecast can be seen here:

    1. Maarten- How geographically large was Ita? Was it a larger-than-average or smaller-than-average tropical cyclone?