Subseasonal Prediction of Significant Wave Heights over the Western Pacific and Indian Oceans: The Impact of MJO and ENSO

This study evaluates the effect of Madden Julian Oscillation (MJO) events and El Niño and the Southern Oscillation (ENSO) on 14-day mean significant wave height (SWH) forecasts at 3 weeks lead-time (Wk34) over the Western Pacific and Indian Oceans using the National Centers for Environmental Prediction (NCEP) Climate Forecast System, version 2 (CFSv2). The WAVEWATCH-3 (WW3) model is forced with daily 10m-winds predicted by a modified version of CFSv2 that is initialized with multiple ocean analyses in both January and May for 1979-2008. A significant anomaly correlation of predicted and observed SWH anomalies (SWHA) at Wk34 lead-time is found over portions of the domain, including the central western Pacific Ocean (WPO), South China Sea (SCS), Bay of Bengal (BOB) and southern Indian Ocean (IO) in January cases, and over BOB, central WPO, the Maritime Continent and southern IO in May cases. The model successfully predicts almost all the important features of the observed composite SWHA during El Niño events in January, including negative SWHA in the central IO and northern WPO, and positive SWHA over the southern Ocean (SO) and central WPO. The model also captures the inverse relationship between SWHA and sea level pressure anomalies during composite of the MJO, El Niño events and La Niña events at Wk34. The model successfully predicts the sign and magnitude of SWHA at Wk34 lead-time in May over the BOB and SCS in composites of phases 2 and 6 of MJO. The observed leading mode of SWHA in May and the third mode of SWHA in January are influenced by the combined effects of MJO and ENSO. Based on spatial and temporal correlations, the spatial patterns of SWHA in the model at Wk34 in both January and May are in good agreement with the observations over the WPO, equatorial and southern IO, and SO.