The wet winter the American southwest has hoped for as it battles extreme drought and heat is increasingly unlikely to materialize as scientists at the CLIMATE PREDICTION CENTER/NCEP/NWS now predict that a phenomenon known as La Nina will develop for the second year in a row.
Basically, La Nina is colder than normal sea-surface temperatures across the Pacific ocean and balances out the El Niño half of the Southern Oscillation (ENSO). The Oscillation rotates between warm, or El Niño, conditions to cold, La Niña, conditions every two to seven years on average.
As strong trade winds push warm water closer to Asia, this causes an upsurge of cold water from deep below the ocean to the surface off the western side of the Americas. These chilly waters push the Jet Stream northward, making for a warmer winter in the South and a cooler than normal one in the North.
It did not come as a surprise to scientists that we will be seeing a second La Nina winter this year. It began forming in July this year, and NOAA scientists started to see the conditions increasingly develop over the past month. They often occur over a period of two years.
What does this mean in laymen’s terms for winter weather?
For the United States, it looks like La Nina will be bringing us some “unsettling weather,” including a boost in hurricane-favorable conditions that will last longer into the fall. There will be a worsening of already dramatic droughts across the Southwest and a very good chance for a cold and stormy winter in the Northern U.S.
There will also be a possibility of some increased tornado activity in other parts of the U.S. come spring. The South, however, may end up having a warm and dry winter season.
Specifically, Washington state, Oregon, and possibly northern California could see wetter conditions than normal, possibly causing problems if the rain comes as a deluge.
“A lot of times when we talk about whether it was a wet year or dry year, you average the whole season,” said John Fasullo, a scientist at the National Center for Atmospheric Research (NCAR). “But with climate change, you have greater amounts of rainfall being delivered in shorter bursts.”
The La Nina weather system could also intensify the worst effects of the drought much of the American west is already experiencing, including higher wildfire risks and water shortages through 2022. “The warming of the climate has led to the drying of the southwest, so when you do have reduced rainfall the droughts get even worse and more intense,” said Fasullo, noting that a lack of precipitation is only one part of the problem.
