Surprise! This hurricane season isn't really much more active than usual. It just feels like it:
Bottom Line: From time to time I address the human condition known as recentcy bias. We're all naturally inclined towards it...it's a completely natural thing to think that whatever is significant that's going on right now is somehow or another more meaningful, impactful, extraordinary etc. Truth is, that's almost never the case.
Due to the recent spate of tragic hurricane activity, there's been an inclination to assert that something highly unusual is going on. That's not really the case. Each month during hurricane season I break down how much activity typically takes place and how far through the season we really are based on historical activity. This is from my story from September 1st:
It's the most active month of hurricane season historically...and the absolute historic peak of hurricane season is September 10th. So, let's take a look at how much of the season is really left by using historical storm activity as a guide.
Going back to 1851 and tracking the Atlantic hurricane season there have been 574 tropical storms in September. That accounts for 35% of all tropical storms. The hurricane development is even more skewed towards September activity. There have been 396, or 40%, of all hurricanes that have formed in September.
That's an average 3.5 tropical storms and 2.5 hurricanes during the month. But back to the original question... How far through the season are we statistically?
The answer is only about 33% based on hurricane development and 38% based on tropical storm development. So, we've got a lot more ahead of us but once we cross the mid-point of September, the odds shift the other way quickly.
Ironically, we were hit by Irma on September 10th, the historical peak of hurricane season. Likewise, what we've seen throughout the month and throughout the season is actually, only slightly above average. Here's more information and another way to look at this season.
Since 1851 we've averaged ten tropical storms per year and six hurricanes per year (for an average 12 named storms per year). Right now, we're at number 13. Historically we only average 2.5 tropical storms in October and November and one hurricane. So, we're pacing around 16.5 named storms this season. Over the past twenty years the average has been 15 per year with a high of 28 in 2005 and a low of 8 in 2014.
So, what's different? We've been personally impacted and many of the islands we care about have been far too often in the cross hairs. Do you recall the 2010, 2011 and 2012 seasons being especially active? Probably not unless you were in the north-east during Sandy in the fall of 2012. Yet each of those years we had 19 named storms.
In years when the steering currents are favorable many don't even pay much attention to the tropical activity. In years like this one where storms are steered towards populated areas we care about it seems unusual. In Florida we'd been especially fortunate for more than a decade after being extremely unlucky for two years (04'&05'). Florida averages being hit a hurricane about every 4.5 years and a major hurricane about every 8 years. We went 11 years between hurricanes (Wilma in 05' until Hermine in 2016) and about 12 years between major hurricanes.