Re: La Nina or El Nino.... which is it?
Posted by cypresstx on 9/13/2011, 1:05 pm
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

Summary
~  La Niña conditions are present across the equatorial Pacific.*
~  Sea surface temperature (SST) anomalies have become increasingly negative in the east-central  equatorial Pacific Ocean during the last several weeks.
~  Atmospheric circulation anomalies are consistent with La Niña.
~ La Niña is expected to strengthen and continue into the Northern Hemisphere winter 2011-12.*

* Note: These statements are updated once a month in association with the ENSO Diagnostics Discussion.


NOAA Operational Definitions for El Niño and La Niña

El Niño: characterized by a positive  ONI greater than or equal to +0.5°C.

La Niña: characterized by a negative ONI less than or equal to  -0.5°C.

By historical standards, to be classified as a full-fledged El Niño or La Niña episode, these thresholds must be exceeded for a period of at least 5 consecutive overlapping 3-month seasons.
 
CPC considers El Niño or La Niña conditions to occur when the monthly  Niño3.4 OISST departures meet or exceed +/- 0.5°C along with consistent atmospheric features.  These anomalies must also be forecasted to persist for 3 consecutive months.  
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La Nina or El Nino.... which is it? - BobbiStorm, 9/12/2011, 9:36 pm
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