2015 El Nino set to be one of strongest ever + Video

by Rob Kothe on 17 Nov 2015 A strong and mature El Niño continues in the tropical Pacific Ocean. The majority of international climate outlook models indicate that the 2015-16 El Niño will strengthen slightly before the end of the year and this means it could be amongst the strongest ever.

Models and expert opinion suggest that peak three-month average surface water temperatures in the east-central tropical Pacific Ocean will exceed two degrees Celsius above average, placing this El Niño event among the three strongest previous events since 1950 (1972-73, 1982-83, 1997-98). National Meteorological and Hydrological Services, WMO Regional Climate Centres, and other agencies will continue to monitor the conditions over tropical Pacific for further El Niño evolution and will assess the most likely local impacts across those regions known to be affected by El Niño.

During October, east-central tropical Pacific Ocean surface temperatures have ranged between +1.9 and +2.5 degrees Celsius above average, exceeding El Niño thresholds by around 1.5 degrees Celsius and signifying a strong event. Typically, El Niño events peak late in the calendar year.

Atmospheric indicators of El Niño have maintained consistency and strengthened during recent months. In particular, the atmospheric pressure across the tropical Pacific Ocean has clearly shown a pattern typical of El Niño, indicating a strong coupling between the atmosphere and ocean.

Also, typical El Niño patterns of cloudiness and rainfall near and east of the international dateline developed during the second quarter of 2015 and have remained strong, as has a weakening of the Pacific trade winds. These patterns of cloudiness and rainfall are considered essential in triggering and maintaining El Niño’s global climate impacts.

Historically, a mature El Niño event is likely to have maximum strength between October and January of the following year, and often to persist through much of the first quarter of that year before decaying.

During the last several months, temperatures below the surface of the tropical Pacific to the east of the international dateline have been substantially above average in response to persistent episodes of significant weakening of the trade winds. The far above average sea surface temperatures in the central and eastern tropical Pacific are associated with the upper portion of this subsurface heat, as well as the weakened trade winds.

The current excess subsurface heat is expected to support the maintenance or a further slight increase of these well above average sea surface temperatures during the remainder of 2015. A recent period of particularly marked weakening of the trade winds in the central tropical Pacific Ocean is supporting further increases in the temperatures below the surface, and a possible consequent increase in sea surface temperature in the far eastern tropical Pacific Ocean in late November or December.

Currently, more than three-quarters of the dynamical prediction models surveyed predict three-month average sea surface temperatures in the east-central tropical Pacific to remain near or exceed +2.0 degrees Celsius above average during November and December. Statistical models are predicting a somewhat more conservative peak El Niño strength, with temperatures ranging between 1.7° and 2.2° Celsius above average.

Taking into account both types of models and their known performance characteristics, there is a high likelihood that the current above-average ocean temperatures in the east-central tropical Pacific will continue and likely slightly increase during November or December.

The expected likely peak three-month average strength would place this El Niño event among the three strongest previous events since 1950, and may rank among the two strongest, along with 1982-83 and 1997-98. A careful watch will be maintained on the oceanic and atmospheric conditions over the tropical Pacific in the coming months to better assess the evolution of the strength of the event.

It is important to note that El Niño and La Niña are not the only factors that drive global climate patterns. Further, the strength of an El Niño event does not necessarily closely correspond to its climate impacts occurring in various regions of the world.

At the regional level, seasonal outlooks need to assess the relative impacts of both the El Niño/La Niña state and other locally relevant climate drivers. For example, the state of the Indian Ocean, or the Tropical Atlantic Sea Surface Temperature, are capable of affecting the climate in the adjacent land areas.

In summary:
• As of October 2015, both the ocean and atmosphere over the tropical Pacific indicate the presence of a strong El Niño;

• A majority of the models surveyed and expert opinion suggest the 2015-16 El Niño will either remain steady or strengthen slightly further during November or December 2015;

• The peak three-month average strength of this El Niño, expected sometime during October-December 2015 to December-February 2016, would place it among the three strongest previous El Niño events since 1950, and may rank among the two strongest.

• Impacts from this El Niño are already evident in some regions and are expected to be felt in some of these as well as other regions in the next two to six months;

• El Niño events typically decline and then dissipate during the first and second quarters of the year following their formation. Note that impacts in some regions are still expected during the dissipation phase.

The situation in the tropical Pacific will continue to be carefully monitored. More detailed interpretations of regional climate variability will be generated routinely by the climate forecasting community over the coming months and will be made available through the National Meteorological and Hydrological Services.

WMO El Niño animation