Predictability of Different ISO Forms

We investigate the subseasonal predictability of intraseasonal convective events and their distinct propagation characteristics as defined by Hirata et al. 2013. They found that intraseasonal convection varies significantly on an event-to-event basis, with only half of the all-austral summer events showing propagation characteristics of the canonical MJOs. The rest are falling within two other distinct forms: an eastward decaying mode and an eastward intensifying mode. The predictability of each mode is investigated using hindcasts from the two most advance coupled forecast systems of ECMWF VarEPS and NCEP CFSv2. Moreover, the predictability of the sea surface temperature signature during convective breaks, that is critical for the development of the canonical mode, is also investigated. In both systems, the canonical mode appears to be more predictable, compared to the other two.

Reference: Hirata, F. E., P. J. Webster, and V. E. Toma (2013), Distinct manifestations of austral summer tropical intraseasonal oscillations, Geophys. Res. Lett., 40, doi:10.1002/grl.50632.