WRL Advisory Bulletin

Current ENSO Status in Pacific Ocean

The central and eastern Pacific Ocean is currently experiencing borderline La Niña conditions. The dynamical and statistical models, however, indicate that El Niño conditions are likely to develop through the summer 2014. The models are predicting about 50% chance for El Niño conditions developing six months from now.

Scientists define ENSO state using an index derived from sea-surface temperatures (SSTs) in a specific region in the equatorial Pacific Ocean that indicates whether ENSO is in a warm (El Niño), cool (La Niña), or neutral phase. An index value equal or greater than +0.5 means sea-surface temperatures are above average, and the Pacific is said to be in an El Niño state. If the index reaches or falls below -0.5, the Pacific is in a La Niña state. It is said to be in neutral state if the index remains in the range -0.5 to +0.5.

Historically Speaking
El Niño and La Niña events tend to develop during the period Apr-Jun and
  • Tend to reach their maximum strength during Dec-Feb.
  • Typically persist for 9-12 months, though occasionally persisting for up to 2 years.
  • Typically recur every 2 to 7 years.

For much of the last fall and this winter, the Pacific Ocean stayed in a neutral state. Recent observations indicate that warmer-than-average water temperatures are developing beneath the surface of the tropical Pacific - an early indication of the onset of El Niño conditions.

The last El Niño occurred in 2009—five years ago. Although four years without an El Niño has happened earlier too, longer gaps are not common. From that point of view, there is a good chance that we are heading for an El Nino event this year.

The El Niño Southern Oscillation (ENSO) phenomenon contributes significantly to seasonal climate fluctuations in many regions of the globe. The Indian summer monsoon rainfall has also been found to have good association with prevailing ENSO conditions. The warm phase of ENSO, i.e. El Nino very often causes deficient monsoon. Major droughts have occurred in India in the El Nino years. On the other hand, the cool phase, i.e. La Nina generally experiences normal to excess monsoon. However, there is no one-to-one relationship and exceptions have occurred in the historical period.