How reliable is ENSO's role as a U.S. 'drought-buster'?

The Western and Southern U.S. have been plagued by recurring drought conditions since the inception of the U.S. drought monitor (1999. Since high hopes are repeatedly pinned on ENSO events to deliver a predictable precipitation signal in much of this region, this has raised the stakes every time such an event occurs.

There has not been any shortage of ENSO events either, with weak-to-moderate El Niño (2002-3, 2004-5, 2006-7) and La Niña (2005-6, 2007-9) events coming in rapid succession. While none of these events rose to the intensity of the 1997-98 El Niño or 1998-2000 La Niña, it is of interest to find out whether the ENSO events since then have performed up to reasonable expectations. That is, if one constructs a composite ENSO event response during weak-to-moderate ENSO conditions since 1950, is the fraction of realized seasonal ‘hits' of the last decade higher or lower than that fraction for earlier decades?

This presentation will address this issue for precipitation in the Western and Southern U.S., with a particular focus on drought-ending ('wet') anomalies.