method

NOAA CPC

The Climate Prediction Center of the American weather service. It publishes the weekly Nino indices, the official ONI, the Southern Oscillation Index and the tropical wind and convection indices.
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Description

The NOAA Climate Prediction Center (CPC) is a branch of the U.S. National Weather Service that specializes in monitoring and forecasting climate phenomena on timescales from weeks to seasons. It is best known for its authoritative tracking of El Niño and La Niña events, publishing the official Oceanic Niño Index (ONI) based on sea surface temperatures in the central Pacific. The CPC also releases weekly updates of the Niño 1+2, 3, 3.4, and 4 indices, the Southern Oscillation Index (SOI) based on atmospheric pressure differences, and various tropical wind and convection indices that describe the state of the atmosphere over the equatorial Pacific.

History

The CPC was established in 1995, succeeding the earlier Climate Analysis Center, which had been issuing El Niño advisories since the 1980s. Its operational forecasts have become the global benchmark for seasonal climate outlooks.

How it works

The CPC combines real-time observations from buoys, satellites, and weather stations with computer models to produce these indices. The ONI, for example, is calculated as the three-month running average of sea surface temperature anomalies in the Niño 3.4 region (5°N–5°S, 120°–170°W). When the ONI exceeds +0.5°C for five consecutive months, an El Niño is declared; below -0.5°C indicates La Niña. The SOI is derived from the standardized difference in surface air pressure between Tahiti and Darwin, Australia.

In practice

Its indices are used worldwide to anticipate droughts, floods, and hurricane activity, guiding decisions in agriculture, water management, and disaster preparedness.

Fun fact

The CPC's weekly ENSO update is read by millions of people, but the 'official' ONI values are only updated monthly, and a single month's value can shift the classification of an entire season.

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