When meteorologists make seasonal forecasts, one of the things they turn to is a relatively reliable, but not perfect, long-term predictor of seasons — water temperatures in the Pacific Ocean.
When the equatorial Pacific is colder than normal, a La Niña climate pattern may develop. When those waters are warmer than normal, an El Niño influence is more likely.
A La Niña contributes, in its classic form, to colder, snowier conditions in parts of the northern United States, while an El Niño tends to send warmer, wetter weather across the southern part of the country.
However, over the past year, the Pacific Ocean temperatures have frustrated forecasters' efforts to generate seasonal outlooks because the patterns haven't followed usual trends.
In recent months, forecasters had believed an El Niño might be developing because waters were warming. That would have been good news, because it could have encouraged weather systems that would ease the drought.
But that hasn't happened, so the thought of an El Niño is off the table for now.
Instead, waters have begun cooling in the eastern Pacific Ocean, hinting that a La Niña could develop.
A La Niña pattern tends to encourage the weather to shift into a drier state, despite its contributions to snow in the north.
The good news is that forecasters aren't projecting a La Niña at this point, because the ocean hasn't gotten chilly enough to make it likely.
Source: National Oceanic and Atmospheric Administration's Climate Prediction Center