La Nina Powers Big Storms

Cyclone Yasi barreled ashore on the Northeast edge of Queensland, Australia this week, where 190 mile-per-hour winds damaged towns guarding the gateway to the Great Barrier Reef. The category 5 cyclone — akin to a hurricane in the U.S. and a typhoon in Asia — was the biggest Australia has seen in over a century. Australian national troops are still trying assess the damage, which includes millions of dollars to sugar cane and banana plantations.

While the summer occurrence of a cyclone like this in Australia is not unusual, the perfect storm set up due to a strong La Nina ocean pattern and very high surface sea temperature, which helped to give the cyclone its energy.

Cyclone Yasi formed near the island of Fiji and blew west into the very warm Coral Sea, where the average sea surface temperature was well above 80 degrees, which is ideal for fueling a big tropical storm.

Just as Yasi was forcing people in northeastern Australia to hunker down, people across two-thirds of the U.S. were feeling the full force of the same La Nina but in a different way.

In the middle of winter, La Nina comes roaring across the U.S. like an icy freight train, delivering a frigid punch. This storm, which extended from New Mexico to Maine dumped over two feet of snow in many places, snarling airports and dragging snow-prone cities like Chicago to its knees.

But is this related to global warming?

Cyclone Yasi is not a direct piece of climate change evidence. But the higher than average sea surface temperatures are likely related to climate change. La Nina events historically bring floods and an increase in cyclones during the Australian storm season from November to April.

Alan Sharp, national manager, tropical cyclone warning services, of the Australian Bureau of Meteorology told Reuters, “We can’t say any particular cyclone is caused by climate change. There has been a slight trend towards more intense storms around the world.”

Scientists agree that there is a likely climate change link to the current La Nina in the form of higher sea surface temperatures. As the world’s oceans have warmed over recent decades that heating is giving monsoons and storms a little extra kick.

Now the naughty La Nina is being blamed for the Blizzard of 2011, which blanketed a large swath of the U.S. in feet of snow, inches of ice and brought major cities to a halt for several days.

Louis Uccellini, director of the government’s National Centers for Environmental Prediction told the Associated Press that this big snow event followed the classic La Nina pattern — moving from the Midwest to the Northeast and redeveloping off the eastern seaboard.

La Nina is a periodic cooling of the surface temperatures of the tropical Pacific Ocean, the opposite of the more well-known El Nino warming.

Both El Nino and La Nina patterns can have major impacts on weather around the world by changing the movement of winds and high and low pressure systems.

Meteorologists knew last fall that a sizable La Nina weather pattern was forming and that it was likely to be a harsh winter in much of the U.S.

Director Uccellini says that while the size and impact on populated areas the storm hit was significant the storm is not unlike other storms that have developed during similar winter weather patterns. He says the Blizzard of 2011 is not a product of climate change.

Mike Halpert, deputy director of the federal Climate Prediction Center says, “The storm is going where we would expect it, according to La Nina.”

The La Nina ocean pattern has peaked and is weakening but meteorologists warn that the little girl will likely stick around for another few months before oceans return to a neutral pattern.