Surreal illustration of a cyclone emerging from the Pacific Ocean.

El Niño's Wild Ride: Why 2016 Tropical Cyclones Defied the Forecasts and What It Means for You

Nico Varela in Climate & Environment August 2025 • 4 min read.

"Unraveling the mystery of extreme weather: How a strong El Niño year turned into a tropical cyclone surprise, challenging climate predictions and revealing the power of Pacific Ocean patterns."

El Niño, the climate phenomenon known for warming the Pacific Ocean, often brings predictable changes to global weather patterns. One common expectation is a quieter tropical cyclone season in the western North Pacific during El Niño's decaying years. However, 2016 defied those expectations. While sharing similar initial conditions with 1998, another strong El Niño year, 2016 saw unexpectedly high tropical cyclone activity, creating a puzzle for meteorologists and climate scientists.

Traditional climate models and forecasts struggled to capture this unusual shift. Several major meteorological agencies predicted an inactive cyclone season, only to witness a surge in activity that broke records and challenged established climate patterns. This unpredictability highlights the complex interplay of various climate factors and their influence on regional weather.

This article delves into the factors that contributed to the surprising tropical cyclone season of 2016. By comparing it against the expected patterns of El Niño years, like 1998, we uncover the key oceanic and atmospheric conditions that led to such a dramatically different outcome. Understanding these factors is crucial not only for refining climate models but also for improving our ability to anticipate and prepare for future extreme weather events.

El Niño's Expected Impact: A History of Quieter Cyclone Seasons

Surreal illustration of a cyclone emerging from the Pacific Ocean.

Typically, El Niño events, particularly in their waning phases, tend to suppress tropical cyclone formation in the western North Pacific (WNP). This is largely due to the development of an anticyclonic circulation (AAC) over the region, which inhibits the atmospheric conditions necessary for cyclone development. In years like 1998, the expected pattern held true: the WNP experienced an extremely quiet season, marked by a lack of cyclone formation during the early months and a significantly reduced number of named cyclones throughout the year.

However, the ocean's surface temperature in 2016 showed features distinct from that in 1998. During July-August, the extremely positive phase of the Pacific meridional mode (PMM) triggered an anomalous cyclonic circulation and negative vertical wind shear over the WNP, favorable for TC geneses, while during September-October, the combined effect of the equatorial western Pacific warming and the weak La Niña event enhanced TC geneses over the WNP.

Anticyclonic Circulation (AAC): A high-pressure system that suppresses rising air, inhibiting storm development.
Vertical Wind Shear: The difference in wind speed and direction at different altitudes, which can disrupt cyclone formation.
Pacific Meridional Mode (PMM): A climate pattern characterized by sea surface temperature variations that can influence atmospheric circulation.

The question then becomes: what factors disrupted the typical El Niño pattern in 2016, leading to such a contrasting cyclone season? The answer lies in the specific sea surface temperature anomalies and atmospheric conditions that unfolded across the Pacific Ocean.

Beyond El Niño: Embracing Climate Complexity

The contrasting cyclone seasons of 1998 and 2016 serve as a powerful reminder that climate predictions are not always straightforward. While El Niño provides a valuable framework for understanding global weather patterns, it is only one piece of a much larger puzzle. Factors like the Pacific Meridional Mode, sea surface temperature anomalies, and even the potential influence of climate change can all interact to create unexpected weather outcomes. Embracing this complexity is essential for refining our climate models and improving our ability to anticipate and prepare for the challenges of a changing world.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1175/jcli-d-17-0263.1, Alternate LINK

Title: Salient Differences In Tropical Cyclone Activity Over The Western North Pacific Between 1998 And 2016

Subject: Atmospheric Science

Journal: Journal of Climate

Publisher: American Meteorological Society

Authors: Ruifen Zhan, Yuqing Wang, Qinyu Liu

Published: 2017-12-01

Everything You Need To Know

How does El Niño usually affect tropical cyclone formation in the western North Pacific?

El Niño typically suppresses tropical cyclone formation in the western North Pacific due to the development of an Anticyclonic Circulation (AAC). This high-pressure system inhibits the atmospheric conditions necessary for cyclone development, leading to quieter cyclone seasons. This pattern was observed in years like 1998, which experienced an extremely quiet season.

What specific oceanic and atmospheric conditions contributed to the unexpected surge in tropical cyclone activity in 2016, despite it being an El Niño year?

The 2016 cyclone season defied the typical El Niño pattern due to several factors. During July-August, the positive phase of the Pacific Meridional Mode (PMM) triggered an anomalous cyclonic circulation and negative vertical wind shear over the western North Pacific, which is favorable for tropical cyclone formation. Later, in September-October, the combined effect of the equatorial western Pacific warming and a weak La Niña event further enhanced tropical cyclone formation in that region.

What are Anticyclonic Circulation (AAC) and Vertical Wind Shear, and how do these atmospheric factors impact tropical cyclone development?

Anticyclonic Circulation (AAC) is a high-pressure system that suppresses rising air, which is necessary for storm development. The presence of an AAC typically inhibits cyclone formation. Conversely, Vertical Wind Shear, which refers to differences in wind speed and direction at different altitudes, can disrupt cyclone formation by tearing apart the developing cyclone structure. Both factors play a crucial role in modulating cyclone activity.

Could you elaborate on the role of the Pacific Meridional Mode (PMM) in influencing tropical cyclone formation?

The Pacific Meridional Mode (PMM) is a climate pattern characterized by sea surface temperature variations that can significantly influence atmospheric circulation. A positive phase of the PMM can trigger anomalous cyclonic circulation, creating conditions favorable for tropical cyclone genesis. Understanding and monitoring the PMM is crucial for improving seasonal weather forecasts and anticipating extreme weather events.

If El Niño's effects are well-known, why did forecasts miss the mark in 2016, and what does this imply about the complexity of climate predictions?

While El Niño provides a framework for understanding global weather patterns, it is only one piece of a larger puzzle. Other factors, such as the Pacific Meridional Mode, sea surface temperature anomalies, and the influence of climate change, can interact to create unexpected weather outcomes. Climate models need to incorporate these complexities to improve our ability to anticipate and prepare for the challenges of a changing world. Furthermore, understanding the interplay between these factors allows for more nuanced and accurate predictions of extreme weather events.