Weather extremes wrought havoc in ’12

Advocate file photo by ARTHUR D. LAUCK -- Residents of Laplace's Cambridge neighborhood flee rising floodwater caused by Hurricane Isaac, which crossed into Louisiana Aug. 28. It was one of the major weather  events of 2012 and left widespread flooding around southeast Louisiana. Show caption
Advocate file photo by ARTHUR D. LAUCK -- Residents of Laplace's Cambridge neighborhood flee rising floodwater caused by Hurricane Isaac, which crossed into Louisiana Aug. 28. It was one of the major weather events of 2012 and left widespread flooding around southeast Louisiana.

In a year that started and ended with severe weather, Louisiana’s 2012 top weather events included drought, Hurricane Isaac and severe storms that brought tornadoes to various parts of the state.

One weather event that affected a large part of the state was Hurricane Isaac, which slowly made its way through the state after making landfall Aug. 28 at the mouth of the Mississippi River.

It was part of a busy hurricane season that surpassed the National Oceanic and Atmospheric Administration’s Climate Prediction Center forecasts, which called for between 12 and 17 named storms. Instead, the 2012 hurricane season resulted in 19 named storms — of which 10 became hurricanes.

This was the third year in a row when the hurricane season, which is from July 1 to Nov. 30, produced 19 named storms.

This year, only four of those storms made landfall in the U.S. — Tropical Storm Beryl, Tropical Storm Debby, Hurricane Isaac and Hurricane/Superstorm Sandy. Both of the hurricanes that made landfall in the U.S. were classified as Category 1 storms, but both did extensive damage because of the storm-associated flooding.

Hurricane Isaac brought flooding to areas far above what used to be predicted in the Saffir-Simpson scale’s Category 1 storms.

Although storm surge heights are no longer tied to the Saffir-Simpson scale because it only measures wind speed, under the old scale a Category 1 storm was expected to produce a 4- to 5-foot surge.

But the slow-moving Hurricane Isaac pushed 13 feet of water into some areas of the coast, Barry Keim, state climatologist, said after the hurricane season ended in November.

Another weather event, a drought in the Midwest, caused low water levels in the Mississippi River.

“That has been a threat for a significant part of 2012. This is not a fleeting thing,” Keim said. “It’s still a problem even to this day.”

According to the U.S. Drought Monitor forecast through March, the drought is forecast to continue in most of the Great Plain states, Keim said.

“As a result, all those rivers that drain into the Mississippi River, there’s not enough water in them,” Keim said. “They’re not expecting a large improvement.”

The third major weather event was the drought that occurred in some parts of Louisiana during most of the year, Keim said.

“We’re probably going to end up with near normal rainfall,” Keim said. However, where and when that rain fell during the year meant that different areas of the state went through regional droughts all year, he said.

According to the U.S. Drought Monitor, as of Tuesday only about 1 percent of the state was considered in drought.

The next three weather events on Keim’s list were short-lived storms that brought severe weather, tornadoes and damage to various parts of the state.

On March 21 and March 22, a slow moving cold front traveled across Louisiana, creating severe weather, flooding and 13 tornadoes during a two-day period.

Heavy rainfall and flash flooding were also a problem across the state during that storm, including 15.9 inches of rain measured in Leesville, Keim said.

On Jan. 25, a winter coastal storm occurred when a warm front followed by a cold front produced nine tornadoes, primarily in the western coastal parishes.

Finally, the Christmas Day storm occurred when two cold fronts draped across the state producing severe weather, including tornadoes in Catahoula, East Baton Rouge, Jefferson, Rapides, St. Landry and Vernon parishes.

“It was a wild day,” Keim said.