Photographer: Valery Hache/AFP via Getty Images

A Market-Roiling La Nina Is Dividing World Weather Forecasters

  • Weak Pacific trends leave lots of room for interpretation
  • Every nation has a different way to measure the beginning

A meteorological clash of nations is confounding the world’s commodity markets.

Global weather agencies can’t agree on whether to expect a La Nina event in coming months. The U.S. has backed off its prediction, Australia remains watchful, while Japan has decided La Nina is already here. Disagreements arise because each nation has different standards for measuring the weather.

The ocean-cooling phenomenon -- a shift from last year’s warming El Nino -- can roil commodities markets with dramatic shifts in weather that wreak havoc on demand and supplies. The yes-no-maybe confusion is giving heartburn to natural gas, coal and agricultural traders who depend on forecasts to place bets on whether prices will rise or fall.

“There are billions of dollars of capital at stake,” said Teri Viswanath, managing director of natural gas at PIRA Energy Group in New York.

Gas traders are already banking on a La Nina to help deliver the frostiest U.S. winter since the "polar vortex," a chill that sent prices surging across the U.S. in 2014. And Australia’s coal is headed for the first annual gain in six years, in part on speculation that a La Nina will curb supplies. The last La Nina flooded coal mines in Indonesia and Australia, the world’s two largest exporters of the fuel.

ENSO Phases

La Nina is just one phase in a larger three-part cycle known as the El Nino Southern Oscillation, or ENSO for short. La Nina represents the cool phase, El Nino is when the equatorial Pacific warms, and ENSO Neutral is in-between.

After 2015’s strong El Nino, the Pacific has been cooling, nudging the ocean toward borderline La Nina conditions, said Mike McPhaden, a senior scientist at the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle. The weak trend leaves plenty of room for interpretation.

“Different groups of experts are reading the tea leaves slightly differently and coming up with different evaluations of where we are headed,” McPhaden said. “It’s not like last year’s strong El Nino that rang all the bells and that had everyone in the scientific community on the same page about what was happening.”

Gas prices are so dependent on weather conditions, the market is craving some consistency among the forecasts, Viswanath said. So far, the Pacific isn’t cooperating. For a La Nina to form, the cooling ocean has to also trigger changes in the atmosphere.

Uncertainty Prevails

“ENSO is not an off-on switch,” said Michelle L’Heureux, a meteorologist with Climate Prediction Center in College Park, Maryland. “It is not like when you walk outside and it is raining on you and you can say ‘It is raining.’ It is an incredibly sprawling, complex phenomenon.”

While weather experts agree on what a La Nina is -- a cooling ocean pattern that affects the atmosphere -- where to set the boundaries for measuring the event is where disagreement lies, said Andrew Watkins, supervisor of climate prediction services for the Australian Bureau of Meteorology in Melbourne. “The differences in the operational definitions revolve around the variables and the thresholds we examine to make a declaration.”

Matter of Degree

Weather agencies in the U.S., Australia and Japan have different guidelines on how cool the Pacific needs to get, how long those conditions need to last, and even what parts of the ocean matter in declaring a La Nina. For instance, the U.S. looks for the ocean to cool by 0.5 degree Celsius (0.9 Fahrenheit), while Australia uses 0.8 degree (1.4 Fahrenheit).

Not surprisingly, nation’s often diverge in their conclusions. 

In 2014, Japan declared an El Nino had begun in the Pacific even though it hadn’t yet detected a reaction in the atmosphere. The lack of changes to the ocean’s skies kept the U.S. and Australia from following suit. The U.S. later declared an El Nino in March 2015, with Australia waiting until May to pronounce the event underway.

That’s how you get the Japan Meteorological Agency declaring last week that La Nina is already underway, at the same time the U.S. Climate Prediction Center dropped its watch saying La Nina is unlikely. Tuesday, the Australian Bureau of Meteorology said it’s going to maintain its La Nina watch because it thinks it might still happen.

Ocean Parsing

Japan, looking at a more easterly section of the Pacific than the U.S., determined ocean temperatures in that spot fit its guidelines for a La Nina, according the agency’s website. Based on its own model, the agency believes La Nina conditions will persist through winter.

Computer models show a variety of outcomes, including the failure of the La Nina to develop. The U.S. cited these possibilities in its decision to drop its La Nina watch. But that still doesn’t mean the U.S. is ruling it out. “The chance of a La Nina itself is definitely not zero,” the climate centers’ L’Heureux said last week.

“When you are in a transition period, it is fundamentally healthy for different agencies to have different opinions,” said Australia’s Watkins. It discourages “community group think, and hence keeps us all on our toes." And that will hopefully give everyone more confidence when the weather agencies do agree, he said.