You thought Arizona's summer was extreme? A 'strong' El Niño could supercharge winter

Following a record-hot summer, an unexpected west coast hurricane and an unpredictable Arizona monsoon, meteorologists are now watching conditions in the Pacific Ocean to see how El Niño might affect fall and winter across the West.

This year’s El Niño is expected to grow stronger and last longer, according to the latest outlook by the National Oceanic and Atmospheric Administration. There is a greater than 95% chance that the phenomenon will continue through early next year.

This El Niño is expected to continue strengthening until it reaches its peak sometime between January and March. That’s when the climate pattern can have the biggest effects on weather around the country, experts say.

Summer extremes: Maricopa County heat-associated deaths surpass 200 in 2023

What is El Niño?

El Niño is the name climate and weather scientists have given the warm phase of the El Niño-La Niña Southern Oscillation pattern. This phenomenon develops in a naturally occurring cycle when sea surface temperatures across the east-central equatorial Pacific Ocean climb above average. El Niño is typically associated with extreme weather and above-average precipitation in the western U.S.

ENSO is the most dramatic year-to-year variation of the Earth’s climate system, according to the National Oceanic Atmospheric Administration. The El Niño part of the cycle has the potential to rain down effects on a range of sectors including agriculture, public health, freshwater availability, power generation and economic activity in the United States and around the globe.

The warmer-than-average sea surface temperatures have already likely contributed to increased temperatures around the world, including a record-shattering heat wave in Arizona during July, which contributed to what ended as the hottest summer on record.

The global surface temperature for August was 2.25 degrees above average, making it the warmest August in NOAA’s 174-year global climate record. August was the fifth consecutive month that global sea surface temperatures hit a record high.

Sea surface temperatures across the Pacific can warm by 1–3 degrees Fahrenheit or more during an El Niño cycle, and these warmer conditions can last anywhere from a few months to two years. The unusual warmth is coupled with a slowdown of the easterly trade winds, as well as increased rainfall and a drop in surface air pressure in the central tropical Pacific.

What does an El Niño mean for the winter?

The effects of the El Niño cycle will stretch well beyond the summer months. According to NOAA’s most recent update, there is a 71% chance that this winter's El Niño will be classified as "strong."

The effects of an El Niño winter can vary across the country. The Pacific Northwest is expected to be drier and warmer during these events.

Typically, during El Niño winters, the powerful jet stream that develops over the equator will push more precipitation over the southern third of the U.S., including Arizona, New Mexico and California. NOAA says such conditions in the Southwest are most noticeable between October and March.

While the Southwest is known for its arid conditions, precipitation records over years to decades show dramatic swings from very wet to very dry years. Researchers at the University of Arizona say these yearly shifts, especially during the winter months, can be tied back to the El Niño.

Over the last few decades, scientists' understanding of the impact of El Niño has improved. Most notably scientists can often detect the development of these patterns months before they arrive.

There is still plenty of variability when comparing El Niño events, and there is no guarantee that any given El Niño event will lead to wetter than average conditions, scientists say.

While knowing an El Niño will be present during the winter months, the scientists say there is no guarantee of a wet winter for the Southwest. A very strong El Niño in 2016 did not bring much relief in terms of winter precipitation.

Extreme drought: Lake Mead swelled with winter runoff, but states will still bank Colorado River water

Will an El Niño winter contribute to drought relief?

While El Niño's exact effects on the Southwest remain uncertain, experts say a wetter winter would likely boost snowpack across the West. That could mean more runoff for the rivers that have struggled to keep up with demand in recent decades. Mountain runoff feeds major rivers, including the Colorado River and the Salt and Verde rivers in Arizona.

Experts say it would take more than one above-average winter to reverse a more than two-decade long drought.

Too much precipitation in a short time can also have negative effects, increasing the threat of flooding and landslides that can turn deadly and cause millions of dollars in damage.

The 1993 El Niño left an estimated $50 million in damage, according to the Arizona Geological Survey. U.S. Highway 95 east of Yuma was closed for nearly six months as the swollen Gila River carried heavy runoff from rain.

How has climate change affected ENSO patterns?

While these weather events have been occurring for centuries or longer, scientists believe climate change will likely influence the way the storms develop and the impacts they bring.

A report released earlier this year by the World Meteorological Organization found that worldwide, temperatures will likely surpass record levels within the next five years due to heat-trapping greenhouse gasses.

Earlier this year, Earth experienced its hottest day ever, when average global temperatures reached 62.92 degrees Fahrenheit.

With warmer atmospheric and ocean temperatures, rainfall extremes are projected to shift eastward along the equator in the Pacific Ocean during El Niño events. Arizona and California lie east of the wet band where El Niño typically forms.

Hot, hotter, hottest: NOAA, NASA say Earth endured the most sizzling summer on record in 2023

The 2015-2016 El Niño brought an increase in Pacific tropical storm activity likely due to a warmer climate, but that did not lead to more precipitation over land, experts said.

And while climate change causes shifts in ENSO, these patterns play a big role in global temperatures. Since the Pacific Ocean is the largest body of water on the planet, covering more than 30% of the Earth’s surface, its surface temperatures regulate amphoteric temperatures.

So when the Pacific is warmer than usual, it will push temperatures up across the planet. This year’s El Niño has likely played a role in the record-breaking temperatures experienced around the globe this summer.

But despite the naturally occurring phenomenon, sea surface temperatures have been rising for decades, due to an increase of greenhouse gas emissions. This means during El Niño years, there will likely be even warmer oceanic and atmospheric temperatures than El Nino cycles of the past.

How does NOAA monitor and track El Niño?

Scientists, governments and nongovernmental organizations all collect data about El Niño using a number of technologies, including a network of scientific buoys monitored by NOAA. These buoys measure ocean and air temperatures, currents, winds and humidity. The buoys are in about 70 locations in the southern Pacific Ocean, from the Galapagos Islands to Australia.

These buoys transmit data daily to researchers and forecasters around the world. Using data from the buoys, along with visual imagery from satellites, scientists are able to more accurately predict El Niño and visualize its development and effects around the globe. They hope this data will help develop more accurate predictions about the oceanic patterns in the future and better prepare people for what might happen.

Jake Frederico covers environmental issues for The Arizona Republic and azcentral. Send tips or questions to jake.frederico@arizonarepublic.com.

Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Sign up for AZ Climate, our weekly environment newsletter, and follow The Republic environmental reporting team at environment.azcentral.com and @azcenvironment on Facebook, Twitter and Instagram.

You can support environmental journalism in Arizona by subscribing to azcentral today.

This article originally appeared on Arizona Republic: After extreme summer, El Niño could stir up Arizona's winter weather