Preconditioning of convective coupled Kelvin waves on the CINDY/DYNAMO MJO propagation

A synthesis of TRMM rainfall and ECMWF analysis shows that a preconditioning of the convectively coupled Kelvin wave (CCKW) ahead of the second Madden-Julian Oscillation (MJO2) event observed during the CINDY2011/DYNAMO campaign in November 2011 is important for the MJO2 propagation over Sumatra. The CCKW induced a pair of counter-rotating gyre west of Sumatra which acts to enhance the kinetic and mist static energy of MJO2 needed to overcome the blocking of Sumatra's Barisan Mountain range. The sensitivity of air-sea coupling, cumulus closure, initial condition, and horizontal resolution to the intraseasonal forecast skill of Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS®) is further investigated using a poor-man's ensemble. This COAMPS ensemble forecast carried out to 15 days shows the air-sea coupling acts to retard the eastward propagation of this event. The choice for the convective closure is shown to exhibit more sensitivity on the MJO propagation than simulations conducted with increased horizontal resolution, the primary impact of which leads to an increase in the MJO propagation speed. Members run with a Simplified Arakawa Shubert cumulus scheme (SAS) produced better MJO propagation characteristics when compared to observations than those utilizing the Kain-Fritsch cumulus scheme (KF). The qusi-1D idealized tests showed the primary difference between SAS, COAMPS KF, and ETA KF is the vertical distribution of heat and moisture.