Summary
El
Niño conditions remain moderate strength in the
equatorial Pacific. For the Feb-Apr season in progress
there is an approximately 93% probability of maintaining
El Niño conditions. Probabilities for El Niño
stay above 80% through the Mar-May season, decreasing
to 55-60% by Apr-Jun season and to the climatological
probability of 25% by the Jul-Sep season.
General
Discussion
During
mid-February, the NINO3.4 SST anomaly index continues
at values indicative of a moderate El Niño category,
having weakened slightly from the stronger levels observed
in December and early January. Since mid-October, the
event has maintanined a moderate to strong magnitude,
modulated by intermittently strong westerly wind anomalies
in the western and central tropical Pacific from September
through present. These wind anomalies deepened the thermocline
and substantially increased the SST anomalies in the central
and eastern equatorial Pacific. A significant, although
recently decreasing, accumulation of subsurface heat ensures
the persistence of the current event into April, and possibly
longer. A resurgence of particularly strong westerly wind
anomalies during the first half of February, continuing
presently, is counteracting the decrease of subsurface
heat content and increasing the certainty that El Niño
conditions will persist at least through early April and
more likely through the middle of northern spring.
Out
of a large set of dynamical and statistical forecast models,
all indicate maintenance of El Niño conditions
during the Feb-Mar-Apr season currently in progress. Overall,
based on model forecasts and current observations of the
ocean surface and subsurface, for the coming Mar-Apr-May
season the probability for El Niño conditions is
estimated at 82%, and for ENSO-neutral conditions approximately
15%. Although the SST anomaly strength has weakened somewhat
since its peak, the event continues at moderate strength,
and will likely endure for another 2 months or longer.
courtesy:
iri.columbia.edu
