TIGGE: Comparison of the Prediction of Southern Hemisphere Extratropical Cyclones by Different Ensemble Prediction Systems

Abstract

he prediction of Northern Hemisphere (NH) extratropical cyclones by nine different ensemble prediction systems (EPSs), archived as part of The Observing System Research and Predictability Experiment (THORPEX) Interactive Grand Global Ensemble (TIGGE), has recently been explored using a cyclone-tracking approach. This paper provides a continuation of this work, extending the analysis to the Southern Hemisphere (SH). While the EPSs have larger error in all cyclone properties in the SH, the relative performance of the different EPSs remains broadly consistent between the two hemispheres. Some interesting differences are also shown. The Chinese Meteorological Administration (CMA) EPS has a significantly lower level of performance in the SH compared to the NH. Previous NH results showed that the Centro de Previs?o de Tempo e Estudos Climáticos (CPTEC) EPS underpredicts cyclone intensity. The results of this current study show that this bias is significantly larger in the SH. The CPTEC EPS also has very little spread in both hemispheres. As with the NH results, cyclone propagation speed is underpredicted by all the EPSs in the SH. To investigate this further, the bias was also computed for the ECMWF high-resolution deterministic forecast. The bias was significantly smaller than the lower-resolution ECMWF EPS.