Potential Predictability of the Madden–julian Oscillation

JANUARY 2003 AMERICAN METEOROLOGICAL SOCIETY | S ince its discovery by Madden and Julian (1971, 1972) over two decades ago, the Madden–Julian oscillation (MJO) has continued to be a topic of significant interest due to its complex nature (Madden and Julian 1994) and the wide range of phenomena with which it interacts. The onset and break activity of the Asian–Australian monsoon system is strongly influenced by the propagation and evolution of MJO events (e.g., Yasunari 1980; Lau and Chan 1986; Hendon and Liebmann 1990a,b). Apart from this significant local influence, there are also important downstream influences that arise from the MJO. For example, the development of persistent North Pacific circulation anomalies during Northern Hemisphere winter has been linked to the evolution and eastward progression of convective anomalies associated with MJO events (e.g., Weickmann 1983; Liebmann and Hartman 1984; Weickmann et al. 1985; Ferranti et al. 1990; Lau and Philips 1986; Higgins and Schubert 1996; Higgins and Mo 1997; Mo 2000). In fact, a link has been shown to exist between rainfall variability along the western United States, including extreme events, and the longitudinal position of MJO convective anomalies (Mo and Higgins 1998a,b; Jones 2000; Higgins et al. 2000; Whitaker and Weickmann 2001). In addition, MJO convective activity has been linked to Northern Hemisphere summertime precipitation variability over Mexico and South America as well as to wintertime circulation anomalies over the Pacific–South American sector (Nogues-Paegle and Mo 1997; Mo and Higgins 1998c; Jones and Schemm 2000; Paegle et al. 2000). Recently, studies have also shown that particular phases of the MJO are more favorable than others in regards to the development of tropical storms/hurricanes in both the Atlantic and Pacific sectors (Maloney and Hartmann 2000; Mo 2000; Higgins and Shi 2001). Finally, the passage of POTENTIAL PREDICTABILITY OF THE MADDEN–JULIAN OSCILLATION