Top five wild weather events of 2011

2011 was a year for extreme weather, with 96 declared disasters in the U.S. that caused $52 billion worth of damage and killed more than 1,000 people, according to the Federal Emergency Management Agency and the National Weather Service.

Why was 2011 such a devastating year in terms of storms?

M. Sanjayan, lead scientist at The Nature Conservancy, a non-profit conservation organization, called 2011 was a "perfect storm of events."

"This is not the media hyping something. Things were a lot worse -- three-to-four times worse in terms of big disasters than we've ever seen before. ... We had a la Nina year," Sanjayan said. "We had this thing called oscillation that drifted further South, but we have this underlying factor of climate change that makes everything warm and super-charges the atmosphere. Plus, people today are living in places that sometimes puts them in harm's way (such as a coastline or canyon) ... where we know people will come and rescue us."

What's with the wacky 2011 weather?

And now, The Nature Conservancy's top weather catastrophes of the year:

5. Droughts in the Southern United States

• The drought across the southern United States is the nation's costliest natural disaster this year, at a total of $10 billion (direct losses to agriculture, cattle and structures).
• According to one climatologist, more than 33 percent of the U.S. (excluding Alaska and Hawaii) was in a drought this year -- the nation's highest percentage in almost four years.

4. Arizona's Wallow Fire

• The "Wallow Fire" (part of the wildfire "dirty dozen") was the largest in Arizona history. It burned more than a half-a-million acres in eastern Arizona, forced the evacuations of thousands of people and cost almost $80 million to fight.
  
• Here are a few statistics: Arizona, New Mexico, and Texas all recorded their biggest fires in 2011. More than a million acres burned in Texas in one of them. The five biggest fire years in U.S. history have all occurred since 2004 (including 2011). And more acres were burned in the last decade (2001-2010) than any other decade -- by 28 percent.

3. July Heat Waves

• In July, each state broke at least one all-time temperature record at least one day of the month, affecting nearly 200 million people in the U.S.
• Specifically, 2,712 high-temperature records were either tied or broken in July, compared with 1,444 last year.
• Americans felt the impact through higher bills and reduced spending powe, seeing larger utility bills and having to make or unplanned purchases or get unplanned repairs of air conditioners and fans, which took a toll on disposable income and increased manufacturing costs for many businesses.

2. East Coast flooding from Hurricane Irene

• Hurricane Irene will most likely prove to be one of the 10 costliest catastrophes in the nation's history -- estimates could reach $7 to $10 billion, largely because the hurricane pummeled an unusually wide area of the East Coast.
• According to the National Weather Service, in the second half of the month of May 2011, almost a year's worth of rain fell over the upper Missouri River Basin. Extremely heavy rainfall in conjunction with an estimated 212 percent of normal snow pack in the Rocky Mountains contributed to this flooding event.

1. Deadly Tornadoes in the Midwest and Southeast

• The deadliest of this year's outbreaks occurred in late April. During a four-day period from April 25 to 28, more than 200 tornadoes touched down in five Southeastern states. The deadliest day was April 27, when 316 people died -- mainly in Alabama and Mississippi -- from 122 tornadoes.
• The National Weather Service's preliminary estimate is that there have been approximately 1,665 tornadoes this year. The previous yearly record number of tornadoes was set in 2004, with 1,817.
• The preliminary estimated number of tornado fatalities so far this year is 549.
• The tornado that hit Joplin, a city with a population of 50,000 at dinnertime on a Sunday, was the deadliest single tornado in the country since 1947. National Weather Service records indicate that there were 370 tornado fatalities before the Joplin event. There were 157 fatalities from the Joplin tornado. Roaring along a path nearly six miles long and about a half-mile to three-quarters of a mile wide, the tornado flattened whole neighborhoods, splintered trees and flipped over cars and trucks. Some 2,000 homes and many other businesses, schools and other buildings were destroyed.
• 2011 is preliminarily the fourth deadliest tornado year in U.S. history.

Looking ahead to 2012, Sanjayan predicted its weather is not going to be as severe.

"Climate changes will continue, so you will continue to see droughts," he said. "But I don't think we will suffer from as many tornadoes like last year. So that is the positive news."