Thursday, February 13, 2014

"Catastrophic" Ice Storm Slams the Southeast and Heads North

The US southeast from Alabama through South Carolina was hit with a very unusual ice and snow storm. Officials and forecasters in several states in the Deep South called the storm "catastrophic." The storm is being blamed for at least 15 deaths in the South and hundreds of car accidents.

The winter storm has impacted an area stretching from northern Florida all the way to Maine, but it is being felt most in the South where people are least accustomed to ice and snow. 

Already three quarters of a million people are without power and that number is expected to increase as more ice and snow fall. These power outages could leave people in the cold, dark for days. An ice storm in the Atlanta area in 2000 left more than 500,000 homes and businesses without power. After a snowstorm stranded thousands two weeks ago, the mayor of Atlanta, urged people to stay home. This left the business district virtually devoid of life. The area includes the headquarters for companies like Home Depot, UPS, Delta and Coca-Cola.

President Barack Obama declared a state of emergency in Georgia, ordering federal agencies to help the state and local response during the storm. Georgia also declared an emergency for around half of the state and the National Guard is on standby. More than 70 shelters are now open.

Winter weather woes were apparent all throughout the Deep South and extended all the way up the east coast to Maine. The storm closed much of Washington and dropped as much as 18 inches of snow in some areas. Most schools along the east coast were closed. About 5,771 domestic US flights were canceled and another 1,235 are delayed

Many states in the south have declared an emergency. In North Texas, at least four people died in traffic accidents on icy roads. In northeastern Alabama, two National Guard wreckers were dispatched to help clear jackknifed 18-wheelers on Interstate 65.

Parts of northeast Mississippi could see up to 4 inches of snow. South Carolina, which hasn't seen a major ice storm in nearly a decade, could get a quarter to three-quarters of an inch of ice and as much as 8 inches of snow in some areas. Thousands of flights have been cancelled due to the storm.

At the end of 2013 Toronto and much of southern Ontario suffered from the crippling effects of a massive ice storm. More recently the central European country of Slovenia was encased in a thick layer of ice.

Ice storms can arise whenever warm air is sandwiched between two pockets of cold air (see graphic on the left). one high up in the atmosphere and one at the surface. Precipitation begins as snow high in the atmosphere, it then turns to rain as it falls through the layer of warm air. As the raindrops fall through the cold air at the bottom, they become supercooled, dipping below the freezing point yet remaining in a liquid state. When the droplets of water make contact with a tree or electrical pylons they form a heavy sheet of ice.

Climate change skeptics like to point to cold weather as evidence that the globe isn't warming. However, global average temperatures clearly show that the globe is getting hotter. It is possible and even likely that climate change will increase the likelihood of periods of extreme cold. Despite these cold snaps the planet is still showing an unmistakeable warming trend.

While no individual weather event can be linked to climate change, there may be a paradoxical relationship between cold weather and global warming. In colder climates like Toronto and Slovenia, warmer winter temperatures can increase the intensity and quantity of freezing rain and wet snow. Whereas in warmer climates, such as the US southeast colder than normal temperatures are the catalysts for an ice storm.

A cold snap is thought to be caused by stratospheric warming which can slow the wind speeds of the arctic atmosphere and push the colder air (often called the polar vortex) further south. As the Arctic ice melts the sea absorbs more light/heat from the sun, which in turn alters the jet-stream and shifts the polar vortex southward.

© 2014, Richard Matthews. All rights reserved.

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