(Repeats for wider distribution)
By Karen Braun
CHICAGO Feb 28 The path to another round of El
Niño in 2017 appears to be shortening, as tropical Pacific Ocean
waters have been warming at a substantial rate.
Weather forecasters have been eyeing for a couple of months
a possible return this year of El Niño, which normally comes
around every two to seven years and last occurred in 2015/16.
The El Niño-Southern Oscillation is one of the most widely
followed long-term indicators of climate, as both its warm and
cool phases can trigger varying effects on weather patterns
El Niño, which is associated with warmer-than-normal sea
surface temperatures (SSTs) along the equatorial Pacific, is
known to bring volatile weather to some parts of the world and
is closely watched by agricultural and energy markets. Some
notable impacts include droughts in Southeast Asia and heavy
rains and erosion along the Pacific coasts of North and South
La Niña, the cool phase of ENSO, just concluded its
six-month run last month. In the last several weeks, remnants of
the colder waters have been all but eliminated.
In the week centered on Feb. 22, the SST anomaly was
positive 2.3 degrees Celsius in the Niño 1+2 region, the
easternmost of the four Niño regions, directly off the coast of
Peru. Warming in this region sometimes precedes the onset of El
To put this into perspective, since weekly record-keeping
began in 1990, the only other instances that featured warmer SST
anomalies in this region occurred during the mega-El Niños of
2015/16 and 1997/98, as well as the moderate-to-strong El Niño
in early 1992.
The week centered on Jan. 25, 2017, also recorded a 2-degree
anomaly, so the latest value is not necessarily an outlier. But
if this trend eventually translates into a full-on El Niño later
in the year, the outcome would be unprecedented.
A record-breaking El Niño surfaced in mid-2015 and lasted
through early 2016, after which SSTs dropped off and gave way to
the relatively weaker La Niña event to cap off the year.
But following the previous occurrences of strong El Niño –
1997/98, 1982/83, 1972/73 – the warm cycle did not appear again
until three or four years later. So the possible return of El
Niño this year would present a unique situation against which
there is not much comparable data.
FORECASTS IN FAVOR
This month for the first time, El Niño is the most favored
scenario over neutral or La Niña conditions starting in July or
August, according to the International Research Institute and
the U.S. Climate Prediction Center. The probability for El Niño
between August and October stands at 51 percent, while the
chance of neutral is at 38 percent (reut.rs/2lZbc2H).
But some models are calling for El Niño’s arrival a bit
earlier based on the progression of the SSTs in recent weeks.
Monday’s run of the CFS version 2 model, maintained by the
U.S. National Centers for Environmental Prediction, shows steady
El Niño conditions – SST anomalies of at least 0.5 degree
Celsius – for most of the Northern Hemispheric spring and then a
moderate to strong event in place by the summer (reut.rs/2mx1Vga).
The projections of the CFSv2 should be considered with
caution, however, as the models are run each day with a shifting
10-day period of initial model conditions, meaning the output
can be highly dependent on a small segment of time. However,
other models have been increasingly leaning toward both El Niño
and its earlier onset.
The latest chart of international ENSO forecast models
compiled by IRI and CPC has shifted in a warmer direction
compared with the previous update, and several models suggest
that El Niño could be comfortably in place as early as May (reut.rs/2lZ8Dh7).
The forecast trends are starting to show a divergence
between the statistical and dynamical models, the latter of
which is based on the actual atmospheric and oceanic state
rather than historical tendencies.
Since the dynamical models are now mostly calling for El
Niño by the start of Northern Hemispheric summer, this gives
confidence that environmental conditions are indeed turning
favorable for the quicker return of the warm cycle.
(Editing by Matthew Lewis)