El Niño or La Niña? Here's the difference and what it means for Arizona weather

Meteorologists are monitoring a powerful weather event that could keep Arizona abnormally warm and dry through the winter.

The National Weather Service has issued a La Niña watch , with a 60% chance La Niña conditions will develop by November. If it does emerge, climatologists predict La Niña would continue through January to March.

“We are favoring La Niña conditions to come in,” said Jon Gottschalck, chief of the operational prediction branch at the National Oceanic and Atmospheric Administration.

While climatologists are confident La Niña will emerge within the next month or two, they cannot be certain.

“We’re still a little bit a ways away from having those impacts,” Gottschalk said. “We’re still waiting for those conditions to officially develop in the ocean and then the atmosphere has to respond.”

Here's what to know about the El Niño and La Niña patterns and how they affect the weather in Arizona.

What is La Niña?

La Niña, and its counterpart El Niño, are climatological events that are part of a natural cycle called the El Niño-Southern Oscillation, or ENSO. It represents the relationship between ocean temperatures and atmospheric conditions stemming from the Pacific Ocean.

During a La Niña event, trade winds that blow east to west near the equator intensify. Stronger winds push warm water from the eastern Pacific toward Asia, warming surface temperatures in the western Pacific. This shift summons deep, cold waters in the central and eastern Pacific.

Cool water drawn up from the ocean depths due to the wind shift triggers a chain reaction of weather events. Once the atmosphere responds to the changes in oceanic temperature, there tends to be more tropical rainfall in areas like Indonesia, the Philippines and northern Australia.

During La Niña, the Pacific Ocean tends to have a weaker hurricane season, with a busier season in the Atlantic.

More: La Niña could turn Arizona's hot, dry summer into a warm, dry winter. What to know

What is a La Niña winter like? Is La Niña warm or cold?

La Niña influences weather around the world, but its impacts differ depending on the region.

It tends to produce warmer and drier winters in the Southwest, the central Rockies, the Gulf Coast and the eastern seaboard.

In the Pacific Northwest, New England and the Great Lakes regions, La Niña usually creates wetter winters.

What would La Niña mean for Arizona weather?

If La Niña conditions emerge, Arizona will likely see a drier and warmer winter, but scientists expect this to be a weaker event.

“Typically in the Southwest, with La Niña as you go into the fall or winter, temperatures generally are warmer than normal,” he said. “There’s a pretty strong signal during La Niña events of below normal precipitation in the southwest and southern plains.”

NOAA recently decreased its La Niña odds from 71% to 60% and predicts it will not produce extremely dry and warm conditions in the Southwest.

"La Niña is forming quite slowly, and the slower it forms, the less time it has to actually peak," said Michael Crimmins, a climatologist at the University of Arizona.

While it likely won't be the driest or hottest winter on record, La Niña could still have negative impacts on Arizona.

After an abnormally dry monsoon, Arizona's soils and vegetation are drier. Below-normal winter precipitation could further strain water supplies and worsen next year's wildfire season.

"We're always in a drought, and a La Niña event on the horizon doesn't spell any relief," Crimmins said. "It most likely spells some continued deterioration or sliding towards short-term drought."

More: Can forecasters predict weather 90 days out? Why long-term outlooks are so complicated

This article originally appeared on Arizona Republic: El Niño or La Niña? Here's the difference and what it means for Arizona weather