 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
| LSU researchers investigate sudden weakening of Hurricane Lili
As Hurricane Lili churned toward landfall on the night of October 4, she had escalated from a Category 2 to a Category 4 storm and there was real concern that she might go all the way to the most dangerous level, a Category 5.
In the LSU Hurricane Center, state climatologist Jay Grymes, LSU oceanographer Greg Stone, and others were intently watching the storm, tracking it through the center’s instruments and supplying advice to state emergency officials in preparation for the big hit. “This was a system that was ready to strengthen,” Grymes said. “It had all the factors in its favor. It took on a near perfectly symmetrical shape, which is representative of big storms.” Suddenly and against all expectations, Lili dropped down to a Category 2 storm approximately four hours before making landfall. The considerably weaker hurricane dragged a storm surge across the marshes of South Louisiana and blew through the towns of Kaplan and Abbeville less powerfully than anyone expected, confounding all the predictions and the hurricane models. Hurricane models are no good if they can’t predict how the storm will behave, so Lili’s sudden drop in intensity generated a lot of interest. “One idea was that Lili came over cool water that Isidore churned up, but Greg’s data showed otherwise,” Grymes said. Lili passed right over one of the instruments in Stone's Wave-Current Surge Information System (WAVCIS), one of a series of instruments that measures water temperature, wave height, direction, current speed, and meteorological conditions.
WAVCIS was developed to detect storms while they are still far away from land and gather real-time data from them. WAVCIS showed that the water temperature had indeed cooled because of Hurricane Isidore, which hit just a week prior to Lili. However, the water temperature had bounced back by the time Lili came through. Researchers had to look elsewhere to find the cause of Lili’s slowdown. Grymes has developed another idea about the cause. “A powerful storm is always symmetrical,” he said. “When Lili went from a [Category] 2 to a 4, she was very symmetrical. But an upper-level low [pressure area] on her western flank began to shear off the western edge of the storm. This slowed the winds and perhaps also dried some of the moist air.” Storm prediction has always been more of an art than a science, but systems such as WAVCIS and the Earth Scan Laboratory at LSU are providing data to make it more reliable. WAVCIS showed that Isidore generated 25-foot waves, and Lili generated 45 foot waves. Nevertheless, the waves from Isidore, which was only a tropical storm when he hit, caused more erosion. Data, such as that collected from real storms, will help make the computer models more accurate. Plugging these data into existing models and seeing how far those model predictions deviate from the actual path and intensity of the storm will help give researchers the ability to tweak the models and make them more accurate. It is on these occasions that the LSU Hurricane Center shows how valuable it is to the well-being of the state. With its real-time storm data and advisory capacity to the state Office of Emergency Preparedness, decisions can be made on road closures, evacuation routes, resource allocations, and other procedures that can save hundreds, possibly thousands, of lives. “With WAVCIS, Earth Scan, and the Hurricane Center, we're taking science out of the classroom and applying it to the real world,” Grymes said. Written by: Ron Brown | University
Relations Related Links: LSU Hurricane Center |
