Do intraseasonal oscillations influence the weather during the summer months?
The North American warm season precipitation regime experiences climate variations on time scales ranging from intraseasonal to decadal. During the summer months low-frequency variability in the tropics is dominated by interannual variations associated with ENSO and by intraseasonal variations such as the MJO. Both of these phenomena feature near-global patterns of anomalous atmospheric circulation that are closely related to variations in precipitation in many regions of the tropics and subtropics. The MJO can have a significant impact on regions that experience rainy seasons both during winter and summer seasons. For example, during the Northern Hemisphere summer season the MJO-related effects on the Indian summer monsoon are well documented. MJO-related effects on the North American summer monsoon also occur, though they are relatively weaker. However, the relative influences of ENSO and the MJO on the summer precipitation regime of North America are not well understood. MJO-related