The outlook for 2008 suggests there could be 12-16 named storms, 6-9 hurricanes and 2-5 major hurricanes. The article stresses that this is simply a prediction. Also, this prediction does not tell us how many tropical cyclones will hit U.S. shores (that is impossible to know).
Just for comparison sake, I checked out what Bill Gray at CSU is calling for this hurricane season. His April 2008 forecast suggests 15 named storms, 8 hurricanes and 4 major hurricanes. He also suggests that the entire U.S. coastline has an above average risk for being struck compared the the 20th century mean.
Why will the season be so active?
1. We are in the middle of the peak in the Atlantic Multidecadal Oscillation (1, 2), which simply means we are in a period where sea surface temperatures and wind speeds are favorable for tropical cyclone development.
2. The moderately strong La Nina what brought cooler weather this winter to the easter half of the US, soaking rains to the Ohio and Mississippi River Valleys and a great snow season to the west will also help hurricanes out over the Atlantic this fall. Research has shown that strong vertical wind shear is typically associated El Nino conditions. Strong vertical wind shear is bad for hurricane development because it 1. spreads out the latent heating occurring due to cloud production which needs to be concentrated over for hurricane development and 2. upsets the large-scale vortex of the hurricane. La Nina conditions often produce much weaker vertical wind shear = good for hurricane development.
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