The Atlantic Hurricane Season is almost here, and the various research groups are rolling the dice, throwing their darts, or checking their magic eight balls. Of course I personally sneer at such primitive means and, following my natural inclinations as a student of ancient Rome, engage in augury. My research group tries to avoid the “guess the number of storms” game, especially since the rules on what is a storm change over time (Even some the culprits have admitted this in a recent Journal of Climate paper). Also, there is the not insignificant issue that even knowing the exact number of storms is meaningless from an emergency management perspective – the only thing that really matters is where they go, and even one hurricane will ruin your day. 1992 is the classic example – only 4 hurricanes in the Atlantic, well below average. Of course, one of those hurricanes was Andrew, which was the most expensive storm up to that time. That said, monitoring and forecasting the overall activity does have important research implications for monitoring climate change (assuming a consistent baseline can be established).
So what does this season look like? This year’s auspicia impetrativa is still in progress, however, the signs are there for a busy season since the Atlantic is warm, and it is likely that the El Nino-Southern Oscillation, a major climate cycle in the Northern Hemisphere, will remain in a Neutral state. Both conditions are favorable for strong storms in the Atlantic. Here is a graphic showing the average number of hurricanes per month for various climate states, along with the forecast for this year:
Shown are the two major conditions of the Atlantic (Warm AMO and Cold AMO), and the three ENSO states (La Nina, Neutral, and El Nino), based on historical data back to 1870. The forecast for 2013 in black, as predicted by an ensemble of computer models. As you can see, it is at the upper envelope of the curves, and well above average for all months except June.
What does this mean to the average person? Not much. If you live on the coast, you should prepare each spring as if you are going to get hit, because even in years with below normal activity, you might get hit with a bad storm, and in busy years, all the storms might stay offshore. For the insurance and financial industries (for which we prepare more detailed estimates), it does influence how you handle the issue of reserves. Otherwise, this is mainly just fodder for the 24 hour news cycle and the “everybody panic all the time!” crowd.