MIAMI – Tropical Storm Humberto over the far eastern Atlantic is forecast to become the first hurricane of the 2013 Atlantic hurricane season. The average date for the first hurricane in the Atlantic is August 10th. This is one indicator of 2013 being an inactive season so far.
I prefer to look at something called the Accumulated Cyclone Energy (ACE) index to determine the overall activity. The ACE index accounts for the number, intensity, and duration of storms. Technically, it is the sum of the squares of the maximum wind speed at six-hour intervals for all tropical storms and hurricanes. It is a much more robust parameter than just looking at the number of storms and hurricanes.
According to Dr. Ryan N. Maue's webpage, the average yearly ACE is 104 based on 1981-2010 climatology. If this were an average year, the ACE should be 48 by today. However, the actual ACE calculated for this season so far is only 9.
If you remember, most of the seasonal hurricane forecasters were calling for above average activity. Something will have to change soon or these seasonal forecasts will have a difficult time verifying. But I don't hear anyone complaining.