Atmospheric Precursors of Madden-Julian Oscillation During CINDY 2011 Tim Li, C. Zhao, P. Hsu (IPRC), and T. Nasuno (JAMSTEC) Observed OLR and NCEP/ECMWF reanalysis data reveal different precursors for two Madden-Julian Oscillation (MJO) events that began over the western Indian Ocean (50-60E, 10S-10N) during the CINDY 2011 field campaign. Left: Nine days (Oct. 4-13, 2011) before the first MJO convection began, the most striking feature was the occurrence of anomalous low- level ascending motion, attributed to anomalous warm advection of the mean temperature by anomalous southwestward flow. At the equator, anomalous intraseasonal westerlies occurred during this period. Right: Three days (Nov. 10-13) before the second MJO convection onset, lower- tropospheric specific humidity increased markedly. This low-level moistening was primarily due to the advection of mean moisture by anomalous intraseasonal flow, characterized by pronounced easterlies at the equator. Left: (top) evolution of 20-90-day filtered OLR (top); (middle) vertical motion averaged over western Indian Ocean (50-60E, 10S-10N); (bottom) anomalous wind patterns (vector) and mean temperature (shaded) fields at 850hPa during initiation. Right: Same as left panel except middle plot shows specific humidity anomaly field and bottom plot shows mean specific humidity field.