Cool water and low salinity tend to dampen this ocean circulation and hurricane activity. Despite the team's belief that hurricane activity is increasing, team members called for numbers only slightly above average this year. The 1998 season predicted 10 named storms, six hurricanes and two intense hurricanes in their third and final update issued in August. Long-term statistical averages yield 9.3 tropical storms, 5.8 hurricanes and 2.2 intense hurricanes annually. Given the variables we had and prior historical records, there is no way we could have predicted such an active hurricane season.
Easterly winds tend to inhibit tropical storm formation.
A very dry season in the Sahel region of West Africa in both 1997 and through July 1998. Dry conditions historically are linked with relatively few tropical storms. Residual El Ni o effects in the eastern equatorial Pacific through July. Westerly winds from El Ni o tend to shear the tops off tropical depressions and prevent them from becoming full-fledged storms. The 1998 forecast fell short because global circulation variables that had good predictive value in prior years just didn't work this time.