Hurricane Hunter Gets an Insider's View of Katrina
for National Geographic News
|September 16, 2005|
By the time Hurricane Katrina slammed into the U.S. Gulf Coast on the
morning of August 29, meteorologist Chris Landsea had become very
familiar with the deadly storm.
Landsea, a hurricane expert with the National Oceanic and Atmospheric Administration, made four flights aboard a "hurricane hunter" aircraft into Katrina between August 25 and August 29.
NOAA meteorologists fly into hurricanes aboard specially equipped aircraft to determine a storm's intensity, direction of travel, likelihood of strengthening, and other data.
Hurricane Katrina began August 23 as a tropical depression near the Bahamas. As it moved westward it strengthened into a hurricane.
The storm made landfall August 25 on the southeast Florida coast as a Category One hurricane with winds of about 80 miles an hour (130 kilometers an hour).
Landsea made his first flight into Katrina as it was coming ashore near his home in Miami, Florida, making his interest in the storm that night a little more personal than usual.
"The first flight was a little nerve-wracking," he said. "The storm was rapidly intensifying, and it was likely to become stronger quickly if it didn't hit land soon. It went right over my house."
Trees felled by the storm killed two people in southeast Florida.
The storm then crossed the Florida peninsula and emerged into the Gulf of Mexico in the early hours of August 26. Katrina began to strengthen almost from the moment it touched the Gulf's warm waters.
A hurricane draws its energy from warm water and warm humid air. Its power is diminished by cooler water and upper level windsknown as wind shearthat can hinder the storm's development or tear it apart.
Landsea was flying into the intensifying storm as it churned across the Gulf. It quickly became clear that Katrina was going to turn into a monster hurricane, he says.
"It was apparent [on Friday and Saturday] that when [Katrina] got back into the Gulf, it was going to intensify," Landsea said. "Saturday the conditions looked perfectwarm deep water, no wind shear, and moist air."
On August 27 Hurricane Katrina was a spectacular sight from above. The storm's clouds covered the entire Gulf of Mexico, Landsea said.
By 11 a.m. August 28 Katrina had become a Category Five storm, the most powerful type of hurricane. Its strongest winds were blowing at 175 miles an hour (280 kilometers an hour).
At 5 p.m. the National Hurricane Center issued an advisory describing Hurricane Katrina as a "potentially catastrophic" storm. The storm had started to push a wall of water from the Gulf of Mexico towards land, and the advisory warned of storm surge flooding of 18 to 22 feet (5 to 7 meters).
"It was clear that there was going to be a horrible storm surge across a large region," Landsea said.
Landsea made his last flight into Hurricane Katrina just as the storm was about to slam into the Gulf Coast. The storm's strength had diminished. But Katrina's winds were about 140 miles an hour (225 kilometers an hour) when the hurricane made landfall in Louisiana near the mouth of the Mississippi River.
"One thing that was nice to see was that it was starting to weaken," Landsea said. "It was no longer a Category Five.
"We're not really sure why it started to weaken," he added. "It may have had dry air coming off the continent that weakened it. There may have been wind shear."
Katrina also might have been undergoing an eye wall replacement cycle as it approached landfall, Landsea said. This phenomenon occurs periodically in extremely powerful hurricanes.
The eye wall is the term for the intense thunderstorms that whirl around the center of the hurricane. When a new eye wall starts forming around the existing wall, the event temporarily slows a hurricane's momentum. The storm's winds are weaker for a few hours until the replacement is completed.
"It looked a lot like [Katrina] was trying to go through one of these cycles," Landsea said. "Its eye was fairly lopsided at landfall with most of the rainfall on the north side of the eye wall. The south eye wall was falling apart."
But Katrina's storm surge diminished little, if any, as it came ashore.
"It was a larger system, and the storm surge was spread out over a larger area," Landsea said. "Even though Katrina was starting to weaken before it made landfall, because it was a large system, the ocean takes a while to relax."
Landsea and others aboard that last flight into Katrina initially thought the Gulf Coast had been spared at least some of the hurricane's wrath.
"We were upbeat at the end of the flight," Landsea said. "It wasn't until later that we found out how horrible it had been."
Hurricane Katrina's storm surge broke through the levees protecting New Orleans, flooding about 80 percent of the city. In Mississippi the beachfront cities of Biloxi and Gulfport sustained massive damage.
The death toll is still being tabulated, but it is already more than 700. Damage from Katrina is expected to exceed 200 to 300 billion dollars (U.S.), making it the most expensive hurricane in U.S. history.
Willie Drye is the author of Storm of the Century: The Labor Day Hurricane of 1935, published by National Geographic.
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