HURRICANE IRENE - LESSONS FOR THE NORTHEAST

The very large wind field and high moisture content of Hurricane Irene posed a significant threat to the Northeast. Many here thought that this would be the long-awaited "Big One". However an intrusion of dry air in the Southeast began to weaken the storm. Although it had decreased to tropical storm intensity by New Jersey, damage was far greater than expected. When the moisture-laden winds were lifted up over the hills and mountains of the Northeast, rapid condensation resulted in very heavy rainfall. Regional flash flooding occurred because of the low infiltration rate through the predominantly bedrock surface of the region. Antecedent rainfall had softened the soil so that even tropical storm winds could cause great tree damage, resulting in massive power losses in the region. The heavily - paved surfaces in multiple northeast urban centers resulted in a short stream lag time and flash flooding.

Storm surge levels were just short of the elevation needed to flood the subsurface transport and communications facilities in New York City. Although Irene was only a tropical storm when it reached New York City, It did damage equal to historic Category 1 and 2 hurricanes that made a landfall here in 1821 and 1893. Once again, we saw the significant damage amplification that occurs in the landfall of a northern hurricane.