Hurricane season, the period of elevated tropical storm activity from June 1 to Nov. 30, is upon us again, and the Colorado State University and National Oceanic and Atmospheric Administration (NOAA) teams have issued their annual hurricane season forecasts.  This year’s NOAA forecast warns of a 90 percent chance of an above-normal or near-normal season.

The other renowned name in hurricane forecasts, the Colorado State University team of Dr. Philip Klotzbach and Dr. William Gray, released their hurricane speculations on April 9.  As usual, the CSU predictions fall within the window of the NOAA forecast; their report calls for eight hurricanes and four major hurricanes.  The Saffir-Simpson scale defines a hurricane as a storm with winds above 73 m.p.h and a major hurricane (Category Three or higher) as a storm with winds above 110 m.p.h.

As for the chance of a major hurricane making landfall in the United States this year, the Klotzbach-Gray team estimated the probability at about 135 percent of the long-period average from 1950 to 2000.

In its own yearly release, the NOAA predicted a 65 percent chance of an above-normal season and a 25 percent chance of a near-normal season.  In the “most-likely scenario,” which the report characterized as 60 to 70 percent likely, we can expect to see 12 to 16 named tropical storms, including six to nine hurricanes and two to five major hurricanes.

The predictions of increased activity are based on increased temperatures in the tropical Atlantic Ocean as well as the lingering effects of La Nina, which the experts, including the NOAA Lead Hurricane Seasonal Forecaster Gerry Bell, credit with the decade-plus of increased hurricane activity since 1995.

The NOAA report was delivered with heavy qualifications.  It warns that the predictions are “probabilistic, not deterministic,” and that the “NOAA does not make seasonal hurricane landfall predictions.”

A spotty history

In the past five years, the NOAA and CSU teams have both been less than spot-on in their annual forecasts.  Last year, the NOAA prediction was for seven to 10 hurricanes with two to five major storms — the year had six and two respectively.  In 2006, the report predicted eight to 10 hurricanes with four to six major — there were five and two.  In 2005, the record-shattering year which saw 15 hurricanes and seven major hurricanes, the NOAA had only predicted seven to nine and three to five.

In every one of those years, the prediction of Gray’s CSU team fell within the NOAA window.  Gray’s predictions for number of hurricanes and major hurricanes have not both been within three since 2003.  A simple average would have done better, falling within three in seven of the last 10 years and three of the last five.

You’d also have to go back to 2003 to find a year when the actual number of hurricanes or major hurricanes fell within the “likely” window predicted by the NOAA.  Critics are understandably skeptical of the forecasts’ accuracy — Tom Terry, a meteorologist at Orlando’s WFTV station, was quoted in the Orlando Sentinel as calling the past forecasts “wildly inaccurate.”

The NOAA and CSU teams, however, insist that their methods are in a constant process of refinement, and that the current methods of prediction are the best to date.  In any case, everyone agrees that predicting the location and severity of a major storm landfall months ahead of time is next to impossible, and the best advice is to be prepared for the possibility of a disastrous storm every year.