Historic Oceanic Niño
Index (ONI) &
La Niña Winter Impacts
on United States Weather Patterns
Jan Null, CCM
The Oceanic Niño Index (ONI)
has become the de-facto standard that NOAA uses for identifying El Niño
(warm) and La Niña (cool) events in the tropical Pacific. It is
running 3-month mean SST anomaly for the Nino 3.4 region (i.e.,
Cold events are defined as 5 consecutive months at or below the -0.5o
anomaly. These are further broken down into Weak (with a -0.5 to -0.9
SST anomaly), Moderate (-1.0 to -1.4) and Strong (≤
Winter Impacts (December, January, February, March)
Copyright © 2007, Golden Gate Weather Services.
Reproduction in full or part is prohibited without permission.