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December 12, 2024 (updated early-month)
Alert Status:
La Niña Watch
La Niña conditions are most likely to emerge in November 2024 - January 2025
(59% chance), with a transition to ENSO-neutral most likely by March-May 2025 (61% chance).
DIAGNOSTIC DISCUSSION:
ENSO-neutral continued in November 2024, with near-average sea surface temperatures
(SSTs) observed across the central and eastern equatorial Pacific Ocean
central and eastern equatorial Pacific Ocean.
Similar to the last couple of months, the latest weekly Niño indices
ranged from +0.1°C (Niño-1+2) to -0.4°C (Niño-3). Below-average
subsurface ocean temperatures persisted across the east-central and eastern
equatorial Pacific Ocean.
Over the western and central equatorial Pacific, low-level wind anomalies were
easterly and upper-level wind anomalies were westerly. Convection was suppressed
over the Date Line and was enhanced over western Indonesia. The traditional and
equatorial Southern Oscillation indices were positive. Collectively, the
coupled ocean-atmosphere system reflected ENSO-neutral.
The dynamical models in the IRI
plume
continue to predict a weak and a short duration La Niña, as indicated by
the Niño-3.4 index values less than -0.5°C. This prediction is also
reflected in the latest North American Multi-Model Ensemble (NMME), which
continues to predict slightly cooler SSTs and weak La Niña conditions.
The forecast team leaned toward predicting an eventual onset of weak and
short-lived La Niña conditions, based on the model guidance and current
atmospheric anomalies. Weak La Niña conditions would be less likely to
result in conventional winter impacts, though predictable signals could still
influence the forecast guidance (e.g., CPC's seasonal outlooks).
... Read more at the
NOAA's Diagnostic Discussion
,
CPC ENSO Update, and
CPC's Official Probabilistic ENSO Forecast sites,
all updated at the same time in the early-month.
** Note: IRI's Monthly Ouick Look updates twice
per month and presents the latest update between the (I) early-month CPC official Probabilistic
Forecast (shown in this section) and (II) mid-month IRI Model-Based Probabilistic Forecast
(shown in the following two sections).
(The update of the CPC ENSO diagnostics discussion and forecast is scheduled
for the second Thursday of each month.)
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December 19, 2024 (updated mid-month)
As of mid-December 2024, ENSO-neutral conditions persist in the equatorial Pacific,
and both oceanic and atmospheric indicators remain in an ENSO-neutral state. The
IRI ENSO prediction
plume
forecasts slightly higher chances (59%) for ENSO-neutral conditions for
Dec-Feb, 2025, with a continuation of ENSO-neutral conditions from Jan-Mar, 2025
to Jul-Sep, 2025. For Aug-Oct 2025, no specific ENSO category emerges as favored.
In summary, ENSO-neutral conditions are expected to persist through the boreal
winter, spring, and summer of 2025.
DISCUSSION:
According to the most recent official
CPC
ENSO Outlook (issued on December 12, 2024), the La Niña onset is
forecasted in Nov-Jan 2024, with 59% chances; however, the objective IRI
model-based ENSO outlook forecasts indicate the continuation of ENSO-neutral
conditions for Dec-Feb, 2025. Thus, there is a notable difference between
the probability numbers in the early-month CPC Outlook and mid-month IRI
ENSO forecast. Going further forward, the CPC ENSO Outlook predicts a clear
preference for La Niña during the winter of 2025, followed by a return
to ENSO-neutral (61% chance in Mar-May) state during boreal spring of 2025.
In contrast, the objective IRI ENSO forecasts show a continuation of
ENSO-neutral conditions during the forecast period.
... Read more at the
IRI Technical ENSO Update,
IRI Model-Based Probabilistic ENSO Forecast,
IRI ENSO Predictions Plume, and
IRI Forecast Probability Distribution Based on the IRI ENSO Prediction
Plume sites, all updated at the same time in the mid-month.
** Note: IRI's Monthly Ouick Look updates twice
per month and presents the latest update between the (I) early-month CPC official Probabilistic
Forecast (shown in this section) and (II) mid-month IRI Model-Based Probabilistic Forecast
(shown in the following two sections).
(The update of the IRI ENSO forecast is scheduled for the 19th of each month. If the 19th falls on a weekend or holiday, it is released on the closest business day.)
December 19, 2024 (updated mid-month)
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... Read more
here, where
any specific model can be interactively examined, along with other detailed information.
(The update of the IRI ENSO forecast is scheduled for the 19th of each month. If the 19th falls on a weekend or holiday, it is released on the closest business day.)
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El Niño and La Niña events tend to develop during the period Apr-Jun and they
The spring predictability barrier: Forecasts made at some times of the year generally have higher skill than forecasts made at other times of the year -- namely, they are better when made between June and December than when they are made between February and May. This is a well-known challenge for forecaster and it can impact statistical models more than dynamical models.
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