Those of us on the US East Coast were less than thrilled to hear in the spring that forecasting institutions across the board were calling for an active hurricane season. To add insult to injury, those that issue landfall forecasts also called for an above average chance of a landfalling hurricane along the Atlantic Seaboard. I didn't quite see the support for a repeat of the epic year of 2005, or even 2008, but there were certainly enough indications to suggest that we'd observe Atlantic activity levels comparable to the last 20 or so years.
Yet here we are, September, in the heart of the Atlantic hurricane season, and to date, our hurricane count sits at zero. If we look back just a few years, by this point in 2005, Hurricanes Dennis and Katrina had already struck the Gulf Coast, and by this point in 2008, Hurricane Gustav had made landfall in Louisiana and Hurricane Ike was just days away from devastating the Houston-Galveston metro area. So, in 2013, where are all of our hurricanes?
The answer lies in the tropics. Since June, the atmosphere over the tropical Atlantic has been as arid as the Sahara desert. In order to get a cluster of thunderstorms to develop into a hurricane, several conditions must exist; one of these is a moist atmosphere. The dry, dusty air that has been moving off the African coast since June is producing the opposite conditions over the tropical Atlantic. The African air is being complemented by dry air moving north from Brazil, which is currently experiencing an extreme drought. This one-two punch of dry air over the Atlantic is squashing all potential hurricanes at the moment, even though the ocean temperatures are sufficiently warm.
Is this a harbinger of things to come in the future, where more extreme and frequent droughts in the tropics could possibly lead to more dry air over the Atlantic Ocean, impeding hurricane development? It's way too early to answer that question definitively, but this season has raised new questions to how hurricanes in the Atlantic might respond to climate change.
Furthermore, the season is far from over. We are only now in the true heart of the season, with September being the most active month, and as we remember from years like 1992 and 2012, it doesn't matter how many storms you have. It only takes one hurricane to make a season truly memorable.
Category: Climate/natural disasters: Climate change, Floods/storms