The Southeast Indian Ocean basin (SIEOB; 90 – 135°E) is linked through intra-basin, intra-hemispheric, and inter-hemispheric teleconnections. These teleconnections provide an opportunity to perform seasonal predictions of tropical cyclone (TC) activity in the SEIOB, up to 6 months prior to the beginning of the tropical cyclone season. Many of the known global modes have been assessed as possible predictors, including, Nino 3.4, Nino 4, Southern Oscillation Index, Northern Oscillation Index, Pacific Decadal Oscillation, Quasi-biennial Oscillation, Pacific-North American pattern, North Atlantic Oscillation, and Arctic Oscillation. In addition, the Indian Ocean Dipole, global SSTs, geopotential heights, air temperature, and the u- and v-components of the wind have been investigated as potential predictors.

In this study a seasonal TC prediction scheme is described for a sub-basin of the SEIOB (105 – 135°E; NWAUS), with 19 potential predictors. The final prediction scheme uses a set of 6 predictors, averaged in three-month bins, to make seasonal predictions of TC activity on 1 September in the NWAUS. The prediction scheme developed using the NWAUS tropical cyclones from 1970 to 2004 and cross-validated using the leave-one-out method. The hindcast scheme yielded an RMSE of annual TC numbers of 1.5, compared with 2.4 from a climatology-based prediction scheme. These numbers represent an improvement in skill of the seasonal prediction scheme of 60% over climatology. This large increase in skill relative to climatology is a consequence of a correlation of ~ 0.8 between the hindcast prediction and observed tropical cyclone numbers. Results will be presented of the performance of the seasonal prediction scheme for the 2005, 2006, and 2007 NWAUS TC seasons, which were not included in the development data set and therefore can be used for independent verification.