So, what happened to Irene? Did it fizzle or not? That seems to depend on where you live. If you're on the coast of North Carolina, you were probably pleasantly surprised by how little damage the storm did. But the storm did cause the deaths of 35 people and has 4.5 million people without power as of this morning. And if you're from Vermont or upstate New York, you got more Irene than you bargained for.
There, homes and bridges have been washed away and many roads are under water, making it difficult to get help where it's needed. The flooding is said to be the worst Vermont has experienced since 1927.
So, what happened to all the hype, the boarded-up windows, the shutdown of the subway and the evacuation of much of New York City? Irene just did what most storms do: she was unpredictable. One of the toughest things to predict about a hurricane is not so much its path but its strength. That's because of the number of variables that go into determining a hurricane's strength:
- Wind shear: Wind moving in different directions at different heights -- bad for a hurricane.
- Surface ocean temperature - Warmer water can evaporate more easily to give the hurricane more moisture.
- Deeper ocean temperature - Here again, warmer is better, especially for sustaining a hurricane as it churns up deeper water.
- Humidity - Humid air also gives hurricanes more power.
In Irene's case, what seems to have happened, according to CNN, is that the storm stagnated over North Carolina. Hurricanes can't last long over land -- they need constant nourishment from ocean water to stay intact. Even after the storm moved over the ocean again after leaving North Carolina, the critical eye of the hurricane had fallen apart and couldn't reform. Great news for New Yorkers.
And where was climate change in all this? Likely, it was playing a role in the extra-warm ocean temperatures (~2.5ºF warmer than normal) that stretched as far north as New York, which allowed the storm to make it further north than most hurricanes do.
But maybe the signal is clearer in the bigger picture: Hurricane Irene was the 10th billion-dollar disaster so far this year, putting 2011 over the top for the most $1 billion disasters ever recorded in a year. Other billion-dollar events included tornadoes (no climate change connection), as well as flooding, drought and wildfires, all of which are expected to get worse in a climate changed-world.
So, farewell to Irene as she heads off towards Greenland and hello, Katia. Let's see what you bring...