Comparisons to Carla and Katrina
Ike is larger than Katrina was, both in its radius of tropical storm force winds--275 miles--and in it radius of hurricane force winds--115 miles. For comparison, Katrina's tropical storm and hurricane force winds extended out 230 and 105 miles, respectively. Ike's surge will probably rival the massive storm surge of Hurricane Carla of 1961. Carla was a Category 4 hurricane with 145 mph winds at landfall, and drove a 10 foot or higher storm surge to a 180-mile stretch of Texas coast. A maximum storm surge of 22 feet was recorded at Port Lavaca, Texas. Despite the fact that the center of Carla hit over 120 miles southwest of Houston, the hurricane drove a 15-foot storm surge into the bays along the south side of the city. Ike's maximum surge is not likely to reach the extreme values above 20 feet seen in Hurricane Carla, though.
The total energy of Ike
The amount of water Ike has put in motion is about 10% greater than what Katrina did, and thus we can expect Ike's storm surge damage will be similar to or greater than Katrina's. The way we can estimate this damage potential is to compute the total energy of Ike's surface winds (kinetic energy). To do this, we must look at how strong the winds are, and factor in the areal coverage of these winds. Thus, we compute the Integrated Kinetic Energy (IKE) by squaring the velocity of the wind and summing over all regions of the hurricane with tropical storm force winds or higher. This "Integrated Kinetic Energy" was recently proposed by Dr. Mark Powell of NOAA's Hurricane Research Division as a better measure of the destructive power of a hurricane's storm surge than the usual Category 1-5 Saffir-Simpson scale. For example, Hurricane Katrina hit Mississippi as a strong Category 3 hurricane, yet its storm surge was more characteristic of a Category 5 storm. Dr. Powell came up with a new scale to rate potential storm surge damage based on IKE (not to be confused with Hurricane Ike!) The new scale ranges from 1-6. Katrina and Wilma at their peaks both earned a 5.1 on this scale (Figure 2). At 12:30pm EDT today, Ike earned a 5.2 on this scale, the second highest kinetic energy of any Atlantic storm in the past 40 years. Hurricane Isabel of 2003 had the highest. Note that the figures I quoted in this morning's blog saying Ike had an IKE of 180, 50% higher than Katrina's, were found to be in error due to some bad data from one of the Hurricane Hunter observations (the IKE is an experimental product, after all). Thus, this morning's IKE was actually a little lower than Katrina's.