At the beginning of August, NOAA reaffirmed its prediction that we’d have a “very active” hurricane season this year. But the season began June 1 and we are already into September without a single hurricane. If you go back to 1950, when hurricanes started getting names, there have been only three times that the first hurricane of the season waited until September to form - 2002, 2001, and 1984. So what's up?
One thing that’s up is that based on historical trends, the peak of hurricane and tropical storm activity doesn’t usually come until Sept. 10. And, on average, there tend to be significantly more storms after the peak than before it. Sandy, the second most damaging storm ever to hit the U.S., struck at the end of October.
Still, the season has been awfully quiet—for a few different reasons. One, rounds of dry, dusty air blowing off Africa have inhibited any tropical development. Two, the Madden-Julian Oscillation (MJO) has been in an unfavorable phase to support convection over the open Atlantic. Three, stronger than average westerly winds have sheared tropical waves apart. Short-term weather trends can do that, but they can easily swing over to more favorable conditions for storm formation. The National Hurricane Center warns people who live where hurricanes strike not to relax yet.
Climate scientists, meanwhile, take a longer view: how will hurricane numbers and intensity change as the greenhouse gas emissions continue to warm the planet? The answer: not sure yet.
Since sea surface temperatures have been rising, and the warm ocean is the energy source for hurricanes, you’d think it's guaranteed that hurricanes would get more frequent and powerful as the century progresses. That’s what climate scientists thought at first too, as recently as the mid-2000’s. But recent research says it’s more complicated than that.
Warm water is important for hurricane formation, but wind shear is another factor— and some research shows that wind shear may increase in a warming world. So in recent years, climatologists began to think we’d have fewer Atlantic hurricanes on average, but that the ones that did manage to form would be stronger. Just a couple of months ago, however, even newer research has suggested there will be more and stronger hurricanes on the way.
None of this means the scientists can’t make up their minds. It means that the research is still in progress: the more scientists learn, the more confidence they have in their projections.
But whether or not storms get more or less frequent, or get stronger or weaker, there is one thing that we do know. Between rising sea levels and coastal population growth, whenever hurricanes do make landfall, the damages they inflict will likely be greater.