The world faces its first “triple dip” La Nina of the century, the World Meteorological Organization said, foreseeing that the weather event, which kicked off in September 2020, could last into 2023.
The United Nations agency, in a quarterly update on the so-called El Nino-southern oscillation (Enso) cycle, said that La Nina conditions in the key tropical Pacific monitoring zone had “strengthened”, with trade winds picking up and a key atmospheric pressure signal recovering, after a “sharp decline” last month.
“Anomalously dry conditions have been observed in the central Pacific, with enhanced convection and precipitation over Indonesia and the western Pacific.
“Climate models and expert assessment indicate that La Niña is likely to continue during [the] next six months becoming the first ‘triple-dip’ La Niña of the 21st century,” and only the third since 1950, the agency said.
‘Likely La Niña will persist’
The WMO rated at 70% the chance of La Nina lasting through the September-to-November period, with a 55% chance of it persisting into December-to-February.
“It is likely that the La Niña will persist through boreal [northern hemisphere] winter 2022-23.”
The assessment tallies with those of other observers, such as Australia’s Bureau of Meteorology and the US NOAA, although not all regard the La Nina as having lasted unbroken since September 2020.
The Bureau of Meteorology, for instance, declared an end in June to La Nina conditions, only two weeks ago to declare a La Nina “alert”, meaning it was likely that the weather event would return.
‘Could be worrisome’
The Enso cycle is closely watched by agricultural markets for its influence on weather in major agricultural producing regions.
La Ninas are linked, for instance, to dryness in some eastern parts of Argentina, Brazil and the US, including major corn and soybean-growing areas, but to heavy rains in South East Asia’s palm oil-growing heartland, and in eastern Australia, which is poised for third successive bumper crops of canola and wheat.
In Brazil, the top exporter of the likes of coffee, soybeans and sugar, official weather service Inmet last week issued a long-range weather forecast warning of below-normal rains for southern Brazil, particularly in October and November, important growing months.
If this forecast, which cited La Nina, verifies “the troubling pattern is that it could get drier as they approach the end of the year instead of the normal pattern of getting wetter as the year ends,” said Dr Michael Cordonnier, the respected South America crop watcher.
“A weather pattern such as this could be worrisome for the first corn crop and for the soybeans as well.”
“Last year the first corn crop and soybeans in southern Brazil were impacted by dry weather. It is difficult to predict which crop might be impacted and by how much, but as long as La Nina is present, it increases the unpredictability of the weather during the growing season.”
‘Very dry conditions’
In the US, NOAA meteorologists last week highlighted the impact of La Ninas in particular on the southern US state of Texas, of which 87.2% is in drought, according to official data.
The proportion reached 97.4% in late July.
“La Niña winters tend to bring dry winters and springs to Texas,” which in turn “tend to bring warmer-than-average summers.
“This summer met both criteria, with a persistent La Niña and very dry conditions in the winter and spring.”
Poor growing conditions in Texas, the top US cotton-growing state, have been blamed for disappointing prospects for the 2022 crop, and an official forecast for US supplies of the fibre shrinking to the tightest in nearly a century.