Some observations post-Irene.
1. Forecasting landfall for a hurricane approaching the Atlantic coast is quite difficult. As is usually the case for storms like Irene, the forecast track steadily slipped northward over a period of days, moving from the lower South Carolina coast to the middle of North Carolina. Had Irene's track been just 50 miles further east, it could have missed NC altogether (skirting the Outer Banks) and remained a stronger hurricane as it approached further north.
2. Likewise, forecasting hurricane intensity is difficult. Fortunately for NY and New England, Irene did strike NC first, taking out quite a bit of its energy. But even before it approached NC, Irene weakened a fair amount. In constrast, in 1989, Hurricane Hugo ramped up in intensity just hours before striking Charleston, SC. Better to err on the side of overpreparation, however.
3. There was more time to prepare for Irene than would be the case for some storms. Irene approached at a relatively leisurely pace for an Atlantic hurricane coming at the east coast (less than 15 miles per hour). The 1938 "Long Island Clipper" was going 60 miles per hour when it hit NY. In the future, there could easily be storms where the lead and warning time is half that of Irene.
4. A large storm like Irene is particularly dangerous. Irene was a good sized hurricane, with tropical storm force winds extending a good 200 miles from its center. A storm that size striking the east coast is always going to cause a lot of damage because there are so many people and cities concentrated in the region. Irene sent moderate storm surges over hundreds of miles of coastline; blew down trees over a huge area; and dropped flooding rains on at least ten states.
5. A slightly more powerful version of Irene could cause catastrophic damage. If, as forecast, Irene had strengthened to a Category three storm before landfall, and if it had just missed NC before turning toward the Atlantic Coast, it could have dealt a devastating blow to NY, NJ and/or New England. As it was, as a large tropical storm Irene managed to flood parts of New York City and devastate several NJ beaches. A more powerful storm on the same track could easily have upped the damage ante to $50 billion, or even $100 billion.
6. NYC is ready to take hurricanes seriously--NYC officials treated the threat soberly, as did many--but of course not all--New Yorkers. As illustrated in the Curmudgeon's novelization of a major hurricane striking NYC (Landstrike), the consequences of a major hurricane making a direct hit on the city would be devastating. We just hope there's no backlash in attitudes because the storm ended up a little weaker than advertised.
Fortunately, geography and climate make the odds of a major hurricane striking NYC at any given time quite small. Irene illustrated that point. But, when the big one does hit--and one day it will--the consequences will be devastating.