An image produced by a University of Colorado at Boulder team shows the projected path of Hurricane Gustav as it approaches the warm waters of the Gulf of Mexico's Loop Current and heads toward the Gulf Coast.
"Rapid intensification of hurricanes in the Gulf is often caused by passage over these deep warm-water features," said Robert Leben, an aerospace engineering research professor at CU-Boulder's Colorado Center for Astrodynamics Research, or CCAR. "The most recent National Weather Service forecast track predicts that Gustav will pass close by the Loop Current," he said.
Processed at CCAR, the image was produced with data from satellites that use altimeters to measure sea-surface height to an accuracy of less than one inch. The altimeters bounce microwave pulses from the satellites to the ocean surface and back, allowing researchers to extrapolate ocean temperatures from subtle height changes in the water. According to Leben, the sea-surface height image shows the warm Loop Current standing 20 inches to 30 inches higher than the surrounding water.
"In the Gulf of Mexico, there is a tight correlation between the sea-surface height measured by the satellites and the temperature of the waters," said Leben. "The higher the sea surface is above the mean, the deeper the warm water underneath it."
He couldn't predict the impact the Loop Current might have on Gustav, but in 2005 his research team tracked Hurricane Katrina as it passed through the Loop Current. Katrina gained a huge amount of energy from the unusually warm waters that subsequently increased its maximum winds, said Leben. The storm evolved from a Category 3 hurricane to a Category 5 hurricane in just nine hours by converting heat from the Loop Current into energy, he said.
"A hurricane is like a steam engine," said Leben. "The more heat that is put into it, the faster it is going to run."
The CCAR researchers used data from the U.S.-French Jason-1 satellite, as well as the U.S. Navy's Geosat Follow-On satellite and the European Space Agency's Envisat satellite. They then combined the data with hurricane wind speed and position data from the National Oceanic and Atmospheric Administration to produce the unique image, Leben said.
The CCAR Web site for mapping ocean currents and eddies in the Gulf of Mexico is funded primarily by NASA's Jet Propulsion Laboratory and is used by petroleum corporations as well as educators and the general public, said Leben. The center produces daily maps of changing ocean currents around the world for governments and private businesses.
In both the 2005 image of Katrina's path and the image showing the projected path of Gustav, wind speeds are listed to the left of the path while on the right side are the days.