Hurricane intensity is a weird and in many ways still poorly understood. The Saffir-Simpson scale helps explain things but it doesn’t always tell the whole story:
Hurricane Ike’s winds remain at Category 2 strength, but Ike is a freak storm with extreme destructive storm surge potential. Ike’s pressure fell rapidly last night to 944 mb, but the hurricane did not respond to the pressure change by increasing its maximum winds in the eyewall. Instead, Ike responded by increasing the velocity of its winds away from the eyewall, over a huge stretch of the Gulf of Mexico. Another very unusual feature of Ike is the fact that the surface winds are much slower than the winds being measured aloft by the Hurricane Hunters. Winds at the surface may only be at Category 1 strength, even though Ike has a central pressure characteristic of a Category 3 or 4 storm. This very unusual structure makes forecasting the future intensity of Ike nearly impossible. The possibilities range from a Category 1 storm at landfall–as predicted by the HWRF model–to a Category 4 storm at landfall, as predicted by the GFDL.
The bottom line is scary:
We must assume Ike will intensify to a Category 3 hurricane by landfall, which would likely do $20-$30 billion in damage. The chances of hundreds of people being killed in this storm is high if people do not heed evacuation orders to leave low-lying areas threatened by high storm surges. Ike’s storm surge is going to be affect a huge area and be tremendously destructive.
