WMO El Nino Update


There is a 60% likelihood of an El Niño being fully established
between June and August, increasing to 75-80% for the October to
December period, according to an El Niño Update issued by the World
Meteorological Organization (WMO). Based on advice from National
Meteorological and Hydrological Services, many governments have
already started preparing for the arrival of El Niño, which is
associated with regional-scale drought and flood situations in
different parts of the world and has a warming influence on global
average surface temperatures. Attached is a graph showing El Niño
impacts on temperatures.

El Niño is characterized by unusually warm ocean surface temperatures
in the central and eastern tropical Pacific, coupled with typical
atmospheric circulation patterns. It is a natural phenomenon with a
recurring interval of 2-7 years and has a major impact on the climate
around the world. The last El Niño was in 2009/2010.

Tropical Pacific Ocean temperatures have recently warmed to weak El
Niño thresholds but atmospheric conditions (such as sea level
pressure, cloudiness and trade winds) have remained neutral. This
indicates that El Niño has not yet become fully established, as it
essentially depends on the interaction between the ocean and the
atmosphere. However, atmospheric patterns that are typical of a fully
developed El Niño event on the basin-wide scale are still likely to
appear, according to the WMO Update, which is based on consensus from
experts around the world.

The tropical Pacific Ocean is expected to continue to warm during the
coming months, peaking during the last quarter of 2014. Its potential
intensity remains uncertain, but a moderate strength event currently
appears more likely than a weak or strong one.

“Our understanding of El Niño and La Niña has increased dramatically
in recent years and this knowledge has enabled us to develop very
successful climate services for society. Advance warning has given
governments around the world time to make contingency plans for the
impact of this year’s expected El Niño on the agriculture, water
management, health and other climate-sensitive sectors,” said WMO
Secretary-General Michel Jarraud. “We remain vulnerable to this force
of nature but we can protect ourselves by being better prepared.”

The US National Oceanic and Atmospheric Administration and the Japan
Meteorological Agency’s Tokyo Climate Centre, which is one of WMO’s
regional climate centres, both reported that average global
temperatures in the month of May were the highest on record, even
without an El Niño event.

One explanation for the lack of atmospheric response so far may be
that the sea surface temperatures are above average across virtually
the entire tropical Pacific, not just in the eastern and central
portions. This may be maintaining west-to-east temperature differences
more typical of neutral conditions. The far eastern tropical Pacific
has already had higher than normal sea surface temperatures since May,
causing above average rainfall along parts of the coast of equatorial
South America

The latest outlooks suggest that central tropical Pacific Ocean
surface temperatures are likely to warm further into the third quarter
of 2014, while the atmospheric patterns associated with El Niño are
also expected to form and strengthen.

Consensus from models and expert opinion is that the event will reach
peak strength during the fourth quarter and endure into the first few
months of 2015 before dissipating. The substantially above-average
oceanic heat content beneath the sea surface of the central and
eastern tropical Pacific Ocean, triggered by strong westerly wind
events earlier this year, suggested an event of significant strength.
However, the delayed atmospheric response, and a potential lack of
subsequent westerly wind events in the coming months, may limit the
peak strength of the El Niño.

It is important to stress that no two El Niño events are the same, and
that other drivers also influence climate patterns.  At the regional
level, seasonal outlooks are needed 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 Dipole, or the
Tropical Atlantic SST Dipole, may impact the climate in adjacent land

Locally applicable information will be available via
regional/national seasonal climate outlooks, such as those produced by
WMO Regional Climate Centres (RCCs), Regional Climate Outlook Forums
(RCOFs) and National Meteorological and Hydrological Services (NMHSs).

An international conference on El Niño/Southern Oscillation (ENSO),
co-sponsored by WMO, will be held in Guayaquil, Ecuador, in November
2014, which will seek to improve operational ENSO predictions and
bridge the gaps between global ENSO science and regional processes,
extremes and impacts.

The World Meteorological Organization is the United Nations System’s
authoritative voice on Weather, Climate and Water


ENSO stands for El Niño/ Southern Oscillation. The ENSO cycle refers
to the year-to-year variations in sea- surface temperatures,
convective rainfall, surface air pressure, and atmospheric circulation
that occur across the equatorial Pacific Ocean. El Niño – Spanish for
boy child because was first noticed by Peruvian fishermen in December
and is identified with the Christ Child – and La Niña represents
opposite extremes in the ENSO cycle.

El Niño refers to the above-average sea-surface temperatures that
periodically develop across the east-central equatorial Pacific. It
represents the warm phase of the ENSO cycle. La Niña refers to the
periodic cooling of sea-surface temperatures across the east-central
equatorial Pacific. It represents the cold phase of the ENSO cycle.

The fluctuations in ocean temperatures during El Niño and La Niña are
accompanied by even larger-scale fluctuations in air pressure between
the western and eastern tropical Pacific known as the Southern

During El Niño events, the eastward shift of thunderstorm activity
from Indonesia into the central Pacific can result in abnormally dry
conditions over northern Australia, Indonesia and the Philippines.
Drier than normal conditions are also often observed over southeastern
Africa and northern Brazil, during the northern winter season. During
the northern summer season, Indian monsoon rainfall tends to be less
than normal, especially in northwest India where crops are adversely
affected. Wetter than normal conditions are observed along the west
coast of tropical South America, and at subtropical latitudes of North
America (Gulf Coast) and South America (southern Brazil to central

During an El Niño event in winter, mid-latitude low pressure systems
tend to be more vigorous than normal in the region of the eastern
North Pacific. These systems pump abnormally warm air into western
Canada, Alaska and the extreme northern portion of the contiguous
United States. Storms also tend to be more vigorous in the Gulf of
Mexico and along the southeast coast of the United States resulting in
wetter than normal conditions in that region.