Guy Carpenter Asia-Pacific Climate Impact Centre Predicts Below-Average Cyclone Activity for Australian Region in 2009/10
The Guy Carpenter Asia-Pacific Climate Impact Centre (GCACIC), a joint initiative of Guy Carpenter & Company, LLC, the leading global risk and reinsurance specialist, and the City University of Hong Kong, predicts tropical cyclone (TC) activity in the Australian region will be below-average during the 2009/10 season. The GCACIC briefing indicates that the formation of an El Niño event in mid-2009 is expected to limit tropical cyclone development during the Australian cyclone season, which runs from November 1, 2009 to April 30, 2010.
For this year’s forecast, GCACIC has expanded its scope to include cyclone predictions for the whole Australian region and a sub-region covering western Australia. The research covers all statistical predictions with predictors drawn from a large group of indices that represent the atmospheric and oceanographic conditions during the pre-season, including the El Niño/Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). With El Niño looking set to persist through the Southern Hemisphere summer, and the IOD is currently in a neutral condition, GCACIC notes the former is the dominant factor in determining TC activity during the 2009/10 season.
As El Niño events tend to suppress TC development in the Australian region, below-average activity is forecast for both the entire Australian region and the western Australian sub-region. For the entire Australian region, all ENSO predictors consistently forecast below-normal activity (ranging from 7 to 9). The IOD predictor suggests a near-normal TC activity (predicted number being 10). Therefore, only 8 TCs are expected to develop in this region - significantly below the average number.
A similar forecast is given for the western Australian sub-region. The ENSO predictors suggest a below-normal TC activity, with the predicted numbers ranging from 4 to 6, while the IOD predictor gives a near-normal TC number. Therefore, 5 TCs are forecast for western Australia, which is below the normal number.
As we are currently witnessing an El Niño event, it is interesting to note that TC activity during previous El Niño years has historically been normal or below-normal in the Australian region. Out of the 9 TC seasons associated with El Niño, 6 are associated with below-normal TC activity (TC number less than or equal to 9) and 3 are associated with normal TC activity (TC number between 10 and 12). ENSO’s influence appears to be even more significant for the western Australian sub-region, where all seasons have seen below-normal TC activity (TC number less than or equal to 6), except for the 2004/05 season.
The full GCACIC briefing is available at http://www.cityu.edu.hk/gcacic/Research%20Brief_2009-03.pdf