As you described it here, you are right that it would subtract, but you were picturing the hurricane spinning the wrong way. It goes counterclockwise, so from south to north on the east side, north to south on the west side.
The part that Noah did not mention is the storm surge. On the east side of a north-moving storm, the wind blows toward the shore and piles water up, while on the west side it blows offshore. Instead of saying "the east side is worse," for the more general case, you should say "the right side" relative to the direction it is moving, so for a westward-moving Andrew, the north side is worse, or for a northwestward-moving North Carolina storm, the northeast side is worse.
One common fallacy about storm surge is that it balances with the low pressure of the atmosphere. If this were true, the isolines of storm surge height would exactly match the isobars of surface air pressure. Now, watch this: an extreme pressure drop of 100 mb would be balanced by a 1 m column of water--not so extreme. Instead, storm surge is due to wind stress pushing water horizontally toward shore--the storm surge is in balance when the wind stress equals the pressure gradient force due to the slope of the water surface; thus longer fetch means higher storm surge.
Brent
