Kristen's Classroom: Introduction to climate patterns
AUSTIN (KXAN) - Several factors affect our day-to-day weather, including the amount of clouds versus sunshine, leftover rain in the ground, and a surface cold front, among others. But there are also a few larger-scale, longer-term climate patterns that can give us an idea of what the 'big picture' forecast could look like.
Below are three prominent climate patterns used in long-term forecasting:
El Niño Southern Oscillation (ENSO)
Perhaps the most commonly known atmospheric-oceanic pattern is the El Niño Southern Oscillation (ENSO). ENSO has three phases: “El Niño”, “La Niña,” and “Neutral”. These phases are defined by both atmospheric and oceanic criteria.
- El Niño: above-average sea surface temperatures (SST) in the central and eastern tropical Pacific Ocean and low-level surface winds, which normally blow from east to west along the equator, weaken or reverse direction
- Impacts: Drier over Indonesia but wetter over the tropical Pacific Ocean.
- La Niña: below-average sea surface temperatures (SST) in the central and eastern tropical Pacific Ocean and normal to stronger east-to-west winds along the equator
- Impacts: Wetter weather towards Indonesia while rainfall decreases over the central tropical Pacific Ocean.
- Neutral: tropical Pacific SSTs are generally close to average, or there is a disconnect between the ocean & atmospheric conditions
Madden-Julian Oscillation (MJO)
The Madden-Julian Oscillation is an eastward-moving disturbance of clouds, rainfall, winds, and pressure that travels around the planet in the tropics. From start to finish, it runs on average for 30 to 60 days. Unlike the ENSO pattern, which can last for a few seasons, the MJO varies on a week-to-week basis with the potential for multiple MJO events within a season. The MJO consists of two phases that typically split the planet into halves:
- Convective phase (enhanced rainfall)
- Suppressed convective phase (less rainfall)
The location of the convective phases is often grouped into geographically based stages that scientists number 1-8.
Pacific Decadal Oscillation (PDO)
The Pacific Decadal Oscillation (PDO) is described as a long-lived ENSO pattern that correlates sea surface temperatures with weather over North America. It is said that the pattern shifts every 20-30 years.
- Positive PDO: Cooler than normal temperatures in the interior North Pacific and warm along the North American Coast, and when sea level pressures are below average over the North Pacific
- Negative PDO: Warmer than normal SSTs in the interior North Pacific and cooler than normal SSTs along the North American coast, or above-average sea level pressures over the North Pacific
What are we in now?
As of August 2025, we are currently in a neutral ENSO phase, a negative PDO phase and a weak and a "weak" MJO pattern.
Last week, the odds of a La Niña winter were increased. Read more about that here.