The Madden-Julian Oscillation (MJO) and Precipitation in the Pacific
Northwest: Composites and a Case Study
The Madden-Julian Oscillation (MJO) is the primary mode of large-scale intraseasonal
variability in the tropics. Analysis of the historical record
indicates that the phase of the MJO has a systematic and substantial effect
on intraseasonal variability in precipitation for Oregon and Washington
in the cool season. The MJO is also associated with a statistically
significant enhancement and modulation of floods in early winter.
The MJO event of November-December 2002 is used as a case study. The
time series of precipitation in the Pacific Northwest during this period
resembled that from our composite results, but this case also illustrates
the ambiguities inherent to specification of the amplitude and phase
of the MJO in real-time. While tentative, our results suggest that when
the MJO is active, it can provide practical information for precipitation
outlooks in the Pacific Northwestr on roughly the 10-30 day time scale.
The presenters will also comment on an article on the predictability
of the MJO that appears in the current issue of BAMS, including
its implications for their results. See:
et al. 2003. Potential predictability of the Madden-Julian Oscillation.
Bulletin of the American Meteorological Society 84(1): 33-50