A quick note on terminology for normal people who don't obsess about this stuff:
- ENSO = the El Niño/Southern Oscillation
- ENSO Neutral = the ocean surface temperature anomaly in the ENSO 3.4 region is between +0.5°C and -0.5°C.
- El Niño/La Niña conditions exist when the anomaly is greater than (Niño) or less than (Niña) the half-degree cut-off for neutral.
- A full blown El Niño/La Niña is declared when the conditions persist for three overlapping three-month periods i.e. five consecutive months.
From IRI/Columbia University:
IRI ENSO Forecast
2017 May Quick Look
Published: May 18, 2017
A monthly summary of the status of El Niño, La Niña, and the Southern Oscillation, or ENSO, based on the NINO3.4 index (120-170W, 5S-5N)
Use the navigation menu on the right to navigate to the different forecast sections
By mid-May 2017, the tropical Pacific remained in an
ENSO-neutral state, with above-average SSTs present in the eastern
Pacific Ocean, and near-average SSTs across the central and east-central
part of the basin. The collection of ENSO prediction models indicates
increasing chances of El Niño into the summer and fall of 2017....MORE
Historically Speaking
El Niño and La Niña events tend to develop during the period Apr-Jun and they
- Tend to reach their maximum strength during October - February
- Typically persist for 9-12 months, though occasionally persisting for up to 2 years
- Typically recur every 2 to 7 years
