El Niño/La Niña Update (October 2007)

La Niña conditions are now well established across the central and eastern 

Equatorial Pacific. The magnitude of the current sea surface temperature 

departures from normal in the central and eastern Equatorial Pacific are in the 

middle-range of La Niña events found in the historical record. La Niña 

conditions are most likely to continue at least through the first quarter of 2008. 

Each La Niña event is different in some respect from the other events, but 

some, like this one, are more different from the others. The most substantial 

difference for this event is that sea surface temperatures currently across the 

north of Australia to the Indian Ocean continue to be cooler than normal, 

contrary to those generally found in most La Niña events. In addition, the 

sequence leading up to this event has been unusual, with La Niña conditions 

established only after a break in movement to such conditions during AprilJune. For management of climate risks and climate-related risks during this 

event, it is therefore critical to recognize the specific aspects of the current 

evolving situation and consult regional seasonal climate outlooks that factor in 

both the prevailing La Niña conditions, and other aspects of the climate 

system, such as the unusual conditions prevailing in the Indian Ocean.