Nearly a month ago the National Oceanographic and Atmospheric Administration’s Climate Prediction Center placed 90-percent odds that the current hurricane season would be more active than normal. Things seemed quiet for a while, but the Atlantic Ocean has come through in the past week or so, churning out Danielle, Earl, Fiona and now Gaston (the last three are visible in the accompanying satellite image).

Danielle wandered the high seas before petering out, threatening only an expedition to the Titanic. Earl battered a few islands in the Caribbean and is now menacing the eastern coast of the United States. Fiona remains a tropical storm as yet, and Gaston is just gathering steam as a young tropical depression, his future wide open.

How does this compare to the past? As is so often the case with this sort of question, it depends on your measure. August looks average in terms of the number of storms but produced two major hurricanes, which is double the average from 1944 to 2009. More significantly, “accumulated cyclone energy” – a measure of the overall energy packed into the full suite of storms and hurricanes – was 60 percent above average.

The key to all of this is the temperature of surface waters in the Atlantic (NOAA sums it up with two easy graphics, here and here). Warm waters serve as fuel for storms, so hurricane researchers can make reasonable projections months in advance based on a combination of temperature data and computer modelling. Given that a warmer climate could translate into warmer oceans, this also plays into discussions about hurricanes and global warming.

As far as the forecast goes, we’ll have to wait and see how things play out. Peak season runs from August through October, so we’re just getting started. In the meantime, you can keep tabs on all of the storms at the National Hurricane Center, which also features lots of cool satellite imagery.