From ICAT's website (link below): "Once the total economic damages for each storm are known, we use changes in inflation, wealth, and population to normalize these damages. This normalization method helps to compare all storms equally as if they all struck land in the current year."
Based on the normalized damage $, if these storms struck in 2011, they would comprise the Top 10 Costliest Hurricanes:

http://www.icatdamageestimator.com/toptendamages
Couple of interesting points:
* The Great Miami Hurricane of 1926 would do almost as much damage today as Katrina and the 1900
Galveston hurricane combined if they both hit today too
* If it hit today, the 1900 Galveston Hurricane would be costlier than Katrina
* The 1944 hurricane was a Cat 1 and would do over $48 billion in damage if it hit today (landfall near Sarasota).
* From the rest of the Top 50 costliest storms below, it is clearly possible to have a $15-$25 billion tropical storm - Agnes and Diane hitting New York today would cause that much damage.
* Of the top 50 costliest storms in the U.S., 2 of them hit in June (both tropical storms) and 0 hit in July.
The rest of the Top 50 Costliest Hurricanes (normalized to 2011 $) are as follows:

http://www.icatdamageestimator.com/all- ... earchText=