During the last month the 2009-10 El Niño has essentially transitioned to ENSO neutral conditions. Over the course of the event, the Multivariate ENSO Index (MEI) peaked in JAN/FEB at 1.5, and the Oceanic Nino Index (ONI) peaked in NDJ at 1.8. The mean 5-day averaged November 1 to March 31 relative AAM anomaly was 0.304. The strongest El Niño forcing appeared to have occurred in late January after the active phase of the Madden-Julian Oscillation (MJO) enhanced El Nino convection in the equatorial Pacific. Here's a chart comparing the 2009-10 El Niño to 17 other warm ENSO episodes that have occurred since 1950.

Dynamical and statistical ENSO model forecasts suggest the possibility that equatorial Pacific SSTs will continue to decline, leading to weak to moderate La Niña conditions by late Summer or Fall. A return to El Niño conditions does not appear likely, but cannot be ruled out. In his May MEI discussion, Klaus Wolter points out that the 1957-1958 El Nino, an analog to the 2009-2010 El Niño, rebounded after dropping into neutral territory.

Downtown Los Angeles (USC) has recorded 16.31 inches of rain since the water year began July 1. This is more than an inch above the 1971-2000 annual climate norm of 15.14 inches. Recent runs of the GFS and ECMWF show a negatively tilted trough deepening and moving onshore early next week. At this point it looks like there's a pretty good chance of showers north of Pt. Conception, but only a slight chance down here. We'll see!

Update 05/18/10. Stations in the Los Angeles area generally recorded under a tenth of an inch from this system. Some isolated totals of about 0.25 inch were recorded in Ventura and Santa Barbara county, and Rocky Butte in San Luis Obispo recorded 0.48 inch. Here is an archived copy of a NWS Public Information Statement with some rainfall totals from around the area.

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