The numbers are based on a weakening El Nino that kept things quiet last year as no hurricanes hit the US and only one hurricane made landfall, and that was as a Category 1 storm in Nicaragua in November 2009.
The actual report itself notes an 85% chance for an average to above average season.
NOAA’s 2010 Atlantic Hurricane Season Outlook calls for an 85% chance of an above normal season. The outlook indicates only a 10% chance of a near-normal season and a 5% chance of a below-normal season. See NOAA definitions of above-, near-, and below-normal seasons. The Atlantic hurricane region includes the North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico.Also, there's another factor in play, and that's the ACE formula.
This outlook reflects an expected set of conditions that is very conducive to increased Atlantic hurricane activity. This expectation is based on the prediction of three climate factors, all of which are conducive historically to increased tropical cyclone activity. These climate factors are: 1) the tropical multi-decadal signal, which has contributed to the high-activity era in the Atlantic basin that began in 1995, 2) exceptionally warm sea surface temperatures in the tropical Atlantic Ocean and Caribbean Sea (called the Main Development Region), and 3) either ENSO-neutral or La Niña conditions in the tropical Pacific, with La Niña becoming increasingly likely. In addition, dynamical models forecasts of the number and strength of tropical cyclones also predict a very active season.
The conditions expected this year have historically produced some very active Atlantic hurricane seasons. The 2010 hurricane season could see activity comparable to a number of extremely active seasons since 1995. If the 2010 activity reaches the upper end of our predicted ranges, it will be one of the most active seasons on record.
The NOAA Accumulated Cyclone Energy (ACE) index, which accounts for the intensity and duration of named storms and hurricanes during the season. We estimate a 70% chance that the 2010 seasonal ACE range will be 155%-270% of the median.That gives an idea of how much time a storm exists and its intensity and correlates with the number of storms.
Still, it sounds like an average to slightly above average season prediction and if such storm does make landfall near you, all the usual disaster preparation steps should be taken - meaning to prepare well in advance of the storm and not expect immediate help from authorities in the case of a major hurricane landfall.