For the second year in a row, the world is heading towards a new La Nia meteorological phenomenon. It dries out parts of the already dry and raging western United States and fuels an already busy Atlantic hurricane season.
Only five months after the end of the La Nia event that began in September 2020, the US National Oceanic and Atmospheric Administration announced that a new cooling of the Pacific Ocean is underway.
The natural cooling of parts of the Pacific Ocean in La Nia is behind the warm El Nio pattern, which alters the world’s weather for months and sometimes years. However, changes vary from place to place and are not fixed, they are only trends.
According to a 1999 survey, the United States is more likely to suffer agricultural and drought damage from La Nia than from El Nio or neutral conditions. The study found that US agriculture in La Nias typically spends between $2.2 billion and $6.5 billion.
How strong and how long will it last?
Mike Harpert, deputy director of NOAA’s Center for Climate Prediction, said it has a 57% chance of becoming a moderate La Nia and only a 15% chance of strengthening. He added that La Nias’ second year in a row isn’t usually measured well until the first year, so it’s not likely to be as strong as last year.
Harpert said the La Nia event is expected to continue until spring.
What does this mean for the West?
For the entire southern third of the country, especially in the southwest, La Nia often means dry and hot weather. Western countries have experienced drought for more than 20 years and the situation has worsened in recent years.
But for the Northwest (Washington, Oregon, probably part of Idaho and Montana), the La Nia event means more rain and more relief from drought is likely, Harpert said.
“It’s good for them, but maybe not so good for Central and Southern California,” Harpert said.
The Ohio Valley and northern plane can be damp and cold. La Nia winters also shift winter blizzards farther north, but in places like the mid-Atlantic coast, blockbuster blizzards don’t happen as often.
What about Atlantic hurricane season?
During the La Nia event last year, the Atlantic set a record with 30 named storms. This year, without a La Nia event, the season is still busier than usual, with 20 named storms and only one name left unused on the list of major hurricane names: Wanda.
It’s been quiet for the past few weeks, but “I hope it recovers again,” Harpert said. “Just because it’s calm now doesn’t mean the storm will continue from October through November.”
The La Nia event makes Atlantic weather more active, as one of the major factors in hurricane formation is the wind near its peak. El Nio causes more crosswinds to reduce storm surges, while La Nia has fewer crosswinds, allowing storms to come and grow.
What about the rest of the world?
Much of both Southeast Asia and northern Australia are moist in La Nia — and this is already evident in Indonesia, Harper said. Central Africa and southeast China are dry.
It is expected to remain cold over Western Canada, South Alaska, Japan, the Korean Peninsula, West Africa and Southeast Brazil.
Follow Seth Borenstein on Twitter. @borenbears.
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