Intraseasonal variability of the cool-season North American coastal cyclonic activity

Intraseasonal variability of the cool-season cyclonic activity along the Pacific and Atlantic coast of North America was diagnosed based on the NCEP/NCAR Reanalysis in 29 years (October-March, 1979/80-2007/08). A significant portion of the variance associated with such variability can be attributed to the zonal distribution of convective heating in the tropical Pacific and Atlantic oceans. In particular, eastward propagation of heating anomalies associated with the Madden-Julian Oscillation (MJO) effectively modulates the frequency and average intensity of cyclones that influence the coastal regions. The impact of the anomalies of the cyclonic activity on the likelihood of the occurrence of extreme precipitation and wind events was examined through composite and regression analysis. Further discussions include the implications of such variability for the skill of the subseasonal forecast of coastal rainfall and its potential impact on the disaster prewarning and planning in the coastal regions.