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A NASA Look Back at Hurricane Katrina
08.29.07
 
Hurricane Katrina is the most well known name in recent hurricane history. She was the costliest hurricane in U.S. history and one of the five deadliest hurricanes to ever strike the United States. Throughout her life in August 2005, NASA used satellites to watch her development and assist forecasters. In addition, NASA technology was deployed to aid officials in assessing the damage along much of the Gulf Coast.

These two images show New Orleans a week apart during the water pumping effort.


Images above: The floods that buried up to 80 percent of New Orleans had noticeably subsided by September 15, 2005, when the top image was taken by the Landsat 7 satellite. In the two and a half weeks that had passed since Hurricane Katrina flooded the city, pumps had been working nonstop to return the water to Lake Pontchartrain. As portable pumps were brought in to supplement the permanent pumps already hard at work, as much as 380 cubic meters (380,000 liters or 23,190,000 cubic inches) of water were being pumped out of New Orleans every second, according to the U.S. Army Corps of Engineers.

The progress in draining the city is evident when the September 15 image is compared with an image taken one week earlier. In the lower image, taken by the Landsat 5 satellite on September 7, black flood water covers much of the city. By September 15, the dark flood water had all but disappeared, lingering only in a few sections of the city. The September 7 image does not show the full extent of the flooding. Taken more than a week after the hurricane struck New Orleans, the image shows a flooded city that had already started to drain. In a similar (but cloudy) image taken on August 30, the flood water in St. Bernard Parish, image right, extends almost to the Mississippi River. + High resolution print still of Sept. 15 Credit: Images provided courtesy of the United States Geological Survey Center for Earth Resources Observation & Science (CEROS).


New Orleans floodwaters have long receded, but the population has struggled to return, even two years later. Coastal Louisiana and Mississippi are still rebuilding.

Katrina made first made landfall and crossed the state of Florida as a Category 1 hurricane, she moved back into the Gulf of Mexico and strengthened. Katrina made landfall as a Category 3 hurricane in the extreme southeast Louisiana bayou, near Buras, on August 29, packing maximum sustained winds of 110 knots. She made final landfall on the Louisiana / Mississippi border near the mouth of the Pearl River with sustained winds of 105 knots.

Damages and deaths caused by Katrina as she came ashore were tremendous in Louisiana and Mississippi. Florida's panhandle, Georgia and Alabama also felt significant effects.

On August 29, Katrina weakened rapidly into a Category 1 hurricane after moving inland over southern and central Mississippi. Six hours later, she weakened to a tropical storm just northwest of Meridian, Mississippi. The next day, Katrina turned northeastward over the Tennessee Valley and became a tropical depression. The depression continued northeastward and became an extratropical low pressure system on August 31. That low was absorbed by a frontal zone later that day over the eastern Great Lakes.

Katrina's Category 4 hurricane force winds were observed by NASA's QuikSCAT satellite on August 29, 2005, just before she made landfall. Image left: Katrina's Category 4 hurricane force winds were observed by NASA’s QuikSCAT satellite on August 29, 2005, just before she made landfall. The image depicts wind speed in color and wind direction with small barbs. White barbs point to areas of heavy rain. The highest wind speeds, shown in purple, surround the center of the storm. Measurements of the wind strength of Hurricane Katrina show sustained winds similar to those shown by these QuikSCAT observations, though not identical. This is because the power of the storm makes accurate measurements difficult. The scatterometer sends pulses of microwave energy through the atmosphere to the ocean surface, and measures the energy that bounces back from the wind-roughened surface. The energy of the microwave pulses changes depending on wind speed and direction, giving scientists a way to monitor wind around the world. + High resolution image Credit: NASA JPL

NASA satellites generate a lot of data and information that is used by hurricane forecasters all the time. NASA's satellites look at winds, sea surface temperatures, humidity, rainfall and clouds in storms to get a better understanding of how they're going to behave. After a storm makes landfall, NASA’s Experimental Advanced Airborne Research Light Detection and Ranging (EAARL) system is used to assess damages, as it was after Katrina made landfall.

NASA satellites include QuikSCAT. QuikSCAT provided images of Katrina's winds. Hurricanes need strong currents of rising air to produce strong thunderstorm activity. QuikSCAT can detect rotating surface winds before other instruments, providing early notice of developing storms to forecasters.

Warmer-than-normal sea-surface temperatures are a key player in hurricanes and their development. Ocean surface water temperatures of 80°F or greater fuel the evaporation of ocean water and rising air. That rising, moist air helps create the thunderstorms and helps give birth to tropical cyclones. Before, during and after Katrina, NASA’s Aqua satellite’s Advanced Microwave Scanning Radiometer (AMSR-E) and the Tropical Rainfall Measuring Mission (TRMM) satellite’s Microwave Imager looked at sea surface temperatures through clouds. The Jason-1 satellite altimeter provided data on sea surface height, a key measurement of ocean energy available to encourage and sustain hurricanes.

On NASA’s Aqua satellite, the Atmospheric Infrared Sounder (AIRS) instrument read daily air temperature and humidity. This may lead to improved weather forecasts, forecasts of storm strength, location and tracks, and winds.

TRMM also provided CAT scan-like views of rainfall in Hurricane Katrina. TRMM measures rainfall intensity. TRMM also sees "hot towers" or vertical columns of rapidly rising air that indicate very strong thunderstorms, such as were present in Katrina. These towers are like powerful pistons that convert energy from water vapor into a powerful wind- and rain-producing engine. The taller the towers are, the greater the likelihood of intensification. Once a storm develops, TRMM can help identify the eye beneath layers of clouds and shows how organized and tightly spiraled the rain bands are­key indicators of storm intensity.

This image depicts a 3 day average of actual sea surface temperatures for the Caribbean Sea and the Atlantic Ocean, from August 25 through 27, 2005. Image right: Warm ocean waters fuel hurricanes, and there was plenty of warm water for Katrina to build up strength once she crossed over Florida and moved into the Gulf of Mexico. This image depicts a 3-day average of actual sea surface temperatures (SSTs) for the Caribbean Sea and the Atlantic Ocean, from August 25-27, 2005. Every area in yellow, orange or red represents 82 degrees Fahrenheit or above. A hurricane needs SSTs at 82 degrees or warmer to strengthen. The data came from the Advanced Microwave Scanning Radiometer (AMSR-E) instrument on NASA's Aqua satellite. Click on image above to view an animation which depicts the sea surface temperatures for the period June 9 through August 9, 2005. Also note the different tracks of Hurricanes Dennis, Emily, and at the very end Katrina. + High resolution print still Credit: NASA/SVS

All of these satellites were providing imagery during Katrina, and helping forecasters refine their predictions for the tracks and intensity during the storm's lifetime.

After Hurricane Katrina, NASA’s EAARL system surveyed the Gulf of Mexico coastline. During the week of Sept. 5, 2005, the aircraft took high-resolution observations that can be used to assess the amount of damage to communities and the environment. This activity was conducted at the request of the U.S. Geological Survey in cooperation with the Federal Emergency Management Agency and the Army Corps of Engineers. While making its observations of the land, the EAARL system, carried on a Cessna 310, has the ability to "see" through vegetation, like trees and shrubs, to view the land underneath. Near the coast it can map the beach surface under water. This will help in the recovery of the shoreline and help determine hazard areas and areas where the environment was damaged.

 
 
Rob Gutro
Goddard Space Flight Center