Looking Back at the Atlantic Hurricane Season Predictions

Four organizations produce predictions about the North Atlantic hurricane season each year. The most followed season forecast comes from the team at Colorado State University, including Dr. William Gray and Phillip Klotzbach. NOAA got into the act in the late 1990s. The Cuabn Meteorological Institute issues one. Lastly, a British risk management and insurance firm called Tropical Storm Risk (TSR) also produces a forecast.

Dr. Gray and Phil Klotzbach adjust their full season forecasts monthly at the first of August, September and October. The first forecast that you really pay attention to is the one issued at the end of May. In that forecast, the CSU team prognosticated 17 named storms, 9 hurricanes and 5 major hurricanes (category three and higher.)

In August, they called for 15 named storms, 8 hurricanes and 4 major hurricanes. They dropped the forecasted number of hurricanes to 7 on their early September update. The October update increased the projected number of named storms to 17, hurricanes kept at 7 and major hurricanes decreased to 3. The NHC has indicated that they will likely upgrade Karen to a hurricane on their post season analysis.

The long term averages are 10 named storms, 6 hurricanes and just under 2.5 major hurricanes each year.

So far, we have experienced 14 named storms, six hurricanes (if you count Karen) and 2 major hurricanes (both Cat 5.)

Another important measurement of the annual tropical cyclone activity is the accumulated cyclone energy average (ACE.) It is an approximation of the energy used by tropical cyclones. It takes into account the numbers, intensity and duration of tropical cyclones.

The long term average ACE for the North Atlantic season is 96.2. The ACE forecasts in May, September and October were 170, 150, 148 and 100 respectively. This means that although there has been a large number of named storms, the total energy released by this season’s tropical cyclones has been average.

These counts indicate that the 2007 North Atlantic Hurricane season has indeed been a busy one, above the long term averages. But fortunately, the environmental conditions over the Atlantic have been such that powerful, long lived hurricanes have been the exception rather than the norm.

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