Americans looked to the past when preparing for Hurricane Irene, and this preparation helped save both money and lives.

“I think people really learned their lesson after Hurricane Katrina,” said Cinzia Cervato, professor of geological and atmospheric sciences. “They learned that it’s better to be safe than sorry.”

Birth of a hurricane

Hurricane Irene, like other hurricanes, began as a tropical depression off the coast of Africa. A tropical depression is a low-pressure system of clouds and thunderstorms that occurs when there is a disturbance in the easterly waves.

“A hurricane first needs something to organize it,” said William Gutowski, professor of geological and atmospheric sciences. “Easterly waves organize thunderstorms, and rotates some.”

Once organized, a tropical depression has the potential of becoming a tropical storm. A tropical storm differs from a regular thunderstorm in that a tropical storm has rotation and, most notably, sustained wind.

The Azores High is responsible for the tracks that tropical storms or hurricanes take over the Pacific Ocean, Cervato said. A small high will cause tropical storms and hurricanes to remain over the Pacific Ocean. A large high will lead the storms into the Gulf of Mexico.

As a tropical storm travels across warm water, water evaporates, vapor forms and tropical storms use that water vapor for energy. When wind speeds increase to more than 74 mph, a tropical storm is then classified as a hurricane.

Hurricanes are classified on the Saffir-Simpson Hurricane Scale into five categories based on the storm’s sustained wind speeds. A Category 1 hurricane has winds speeds between 74 to 95 mph while a Category 5 hurricane has wind speeds more than 155 mph.

“It’s just a convenient way to classify,” Gutowski said of the scale. “It’s one aspect of it — the speed of wind.”

Problems with Irene

Gutowski said there are many more aspects to consider when trying to predict the potential damage that could be caused by a hurricane. For instance, in the case of Irene, the track of the storm was problematic.

“There’s this corridor of densely populated cities on the East Coast,” Gutowski said. “And Irene was traveling right along it.”

Another worry for public officials was the fact that hurricanes do not hit the East Coast as often as they do Florida or New Orleans, Gutowski said.

“There was concern that the infrastructure might not be prepared for it,” he said.

Heeding the warning

In the days before Irene made landfall, people on the East Coast prepared for the worst. Several governors declared states of emergency and asked residents in dangerous regions to evacuate. Even without being asked, many other people on the coast packed their belongings and headed inland.

“People paid attention,” Gutowski said. “People responded individually to the warnings.”

In contrast, when Hurricane Katrina occurred, many people in New Orleans ignored the warnings.

“They thought, ‘We’ve been through hurricanes before. It can’t be that bad,'” Cervato said. “Nobody moved. Very few people packed up and left.”

New Orleans is also below sea level, which means that the area is more susceptible to flooding. In addition to high winds, hurricanes also bring storm surges.

Storm surges are abnormal rises in sea level that result from strong winds. As a storm surge nears land, it become larger. Eventually, it crashes into the shore and the water spreads across the land, taking with it anything in its way.

“Storm surges do the most damage,” Cervato said.

During Hurricane Katrina, which was a Category 3 hurricane when it made landfall in Louisiana, storm surges reached more than 20 feet tall. These storm surges flooded New Orleans and caused collossal damage to the entire Gulf Coast region.

In fear of storm surges, New York City Mayor Michael Bloomberg ordered the mandatory evacuation of nearly 370,000 residents in low-lying regions of the city. When Irene made landfall in the Coney Island area of Brooklyn, after having already made landfall in North Carolina and New Jersey, the hurricane had been downgraded to a tropical storm.

“The combination of warnings and the down class to tropical storm was a good thing,” Cervato said.

Officials warned that storm surges could have reached more than 8 feet tall. However, Irene lost energy as it traveled up the East Coast, and the storm surges reached only about 5 feet across the region, which led to less damage that had been predicted.

Although critics say that Bloomberg acted unreasonably when he called for the mandatory evacuation of so many residents, Gutowski feels that Bloomberg made a smart decision.

“There could have been a small shift in the storm and storm surges could have been much worse,” he said.

Cleaning up after Irene

With the storm over, residents on the East Coast must now deal with the damage dealt by Irene. Flooding and power outages are two of the biggest problems that were caused by the storm, Cervato and Gutowski said.

“The cleaning up process is: wait for water to retreat, clean up debris and rebuild,” Cervato said.

Gutowski said that floodwaters are often contaminated. He said public officials must provide citizens with fresh, clean water. He said that officials must also provide food for people who do not have access to a working refrigerator due to power outages.

During the rebuilding process, Gutowski recommended that citizens avoid dangerous areas and doing actions that will put them at risk.

“If you do something dangerous, you put yourself at risk, but you also put emergency crews at risk,” he said. “And, you take them away from helping someone who is in danger from no fault of their own.”

As cleanup begins, many people will talk about the damage caused by Hurricane Irene. According to the Associated Press, there are 38 confirmed deaths due to Hurricane Irene. And Reuters reported that the storm could cost billions of dollars in damage.

However, those numbers are significantly lower than those produced by Hurricane Katrina. The National Hurricane Center reported that 1,836 people died in Katrina or from subsequent flooding and the total property damage amounted to $81 billion.

Cervato and Gutowski both believe that Americans learned from the catastrophe that occurred because of ill preparation for Hurricane Katrina. Although individuals and public officials can mitigate hurricane damage, no one can prevent hurricanes from occurring.

“They’re natural phenomenas,” Cervato said. “It’s just something we have to deal with.”