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Seminar Abstract

Nicholas Bond and Gabriel Vecchi - February 18, 2003


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:

Waliser et al. 2003. Potential predictability of the Madden-Julian Oscillation. Bulletin of the American Meteorological Society 84(1): 33-50

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