Unusual winter slams North Alabama

Florence experienced its third deepest snowfall on record last month.

Jason Lankford Staff Writer

North Alabama has experienced one of its coldest winters in recorded history and Florence received its third deepest snow on record last month, creating problems for an area ill-equipped for such conditions.

“I’m not used to driving on snow, so the road conditions have been very difficult,” said English major Shay Spurgin. “It’s also very frustrating when one day it’s really cold and the next day it’s warm again. I hate the unpredictability.”

Meteorologists are saying that the warm spell North Alabama has experienced during this week is only a break before more freezing temperatures. But what are the causes for this unusual weather and what implications does it have for global warming theory?

According to Dan Satterfield, chief meteorologist at WHNT NEWS in Huntsville, there are two different explanations for the cold weather the eastern U.S. has been experiencing, and both have to do with the storm track.

Satterfield said the first part of the winter was cold and snowy due to the negative phase of the North Atlantic Oscillation (NAO). The NAO is a fluctuation in atmospheric pressure in the North Atlantic Ocean. The negative phase is characterized by lower air pressure and height over the eastern U.S.

This results in lower temperatures and greater amounts of precipitation due to the shifting of the North Atlantic jet stream and storm track.

“The effects vary from year to year,” said Michelle Amin, a meteorologist at the National Weather Service in Huntsville. “In this particular winter, we have a set up in which the jet stream is very low, directing any storm system that develops right into our path.”

According to Satterfield, the lower temperatures and increased snow in late January and February are due to a positive Pacific/North American (PNA) pattern, which is strongly influenced by El Nino. The pattern has results similar to those produced by the NAO.

Kris White, a meteorologist at the National Weather Service in Huntsville who is currently researching how weather phenomena have impacted the Tennessee Valley, believes that the oscillation patterns are not the cause of the weather, but the effects of conditions in the Arctic.

“When you get a lot of high pressured, concentrated air continually building, and flowing out of the Arctic, you end up with an exchange of air between the poles,” he said. “We get the cold exchange here and some other parts of the world get the warm exchange.”

The lower temperatures have been confined to certain parts of the world, namely the U.S. and western Europe. Worldwide, January 2011 is tied for the ninth warmest January on record.

The same conditions that created heavy snowfall and freezing temperatures this winter may create a hot and humid summer with increased storm activity.

“We’re in a very strong La Nina event that may create tropical cyclones in increased frequency,” said Dr. Ricardo Nogueira, assistant professor of geography.

Nogueira thinks that it is difficult to assess what effects climate change has had on recent weather conditions on a global scale at this point.

Vladimir Petoukhov, a climate scientist at the Potsdam Institute for Climate Impact Research, recently did a study on climate change in winter. He found that as the ice shelves in the Arctic shrink, the sea absorbs more heat from the sun. The heat flows upward into the polar air, creating a high-pressure system that forces the frigid air into the NAO, channeling it into the U.S.

Biology major Kevin Woods doesn’t believe that the current winter conditions disprove climate change theories, but the changes are not necessarily caused by humans.

“I do believe there are definite implications that there has been climate change over the previous years,” he said. “But the fact of the matter is that the earth has experienced climate change for thousands of years.”