Evaluation of the Eastward Propagating Convective Disturbances

A diagnostic of the intraseasonal variability in the regional models is proposed and evaluated. The metric is based on the two leading EOFs of the eastward moving precipitation anomalies in Indian Ocean and Maritime Continent in the equatorial 15N-15S belt.  The EOFs have a maximum variability in the central Indian Ocean and west of Sumatra and the corresponding PCs describe a moving mode with the 30-60 day period. During the boreal summer the area of calculation can be extended to 30 N to represent the 30-60 day mode of boreal summer ISO (BSISO) and the EOFs exhibit a tilted structure characteristics for BSISO 1 (30-60 day) mode.  The metric based on this approach and other MJO and BSISO metrics are used to diagnose behavior of intraseasonal variability in the Navy coupled prediction systems.  In addition, the EOFs and principal components of the eastward propagating disturbances are evaluated for the “good MJO” and “bad MJO” simulations in the GASS/YOTC data base to examine the relationship between special patterns  of the eastward propagating modes and intraseasonal variability in the Indo-Pacific warm pool area