Intradecadal Variations in Atlantic Hurricane Activity
Strategic Element: Decadal to Centennial Change
Principal Investigator: Chris W. Landsea
Objective: Basic physical understanding and forecasts of seasonal to multidecadal tropical cyclone activity. Climatological atmospheric and oceanic conditions. Economic and societal impact.
Narrative: The North Atlantic is the only ocean in which there is a net northward flow of warm water in all latitudes. Sometimes the flow is saltier and warmer than usual; other times it is fresher and not quite so warm. The salty/warm and fresh/cool phases appear to alternate every 20 to 30 years. During the salty/warm phase, rain falls abundantly in West Africa south of the Sahara, European winters are cold, and hurricane activity increases. During the fresh/cool phase, there are droughts in Africa, mild European winters, and fewer hurricanes.
The period of the late 1940s through the 1960s was a time of many hurricanes. In the 1970s and 1980s, the thermohaline circulation was in the fresh/cool phase and fewer major hurricanes formed. Apparently, the circulation changed back to the salty/warm phase some time between the late 1980s [when Hurricane Hugo devastated South Carolina, and Gilbert set a record (888 mb or 26.22 inches of Mercury) for the lowest sea-level pressure observed in the Western Hemisphere] and the hyperactive 1995 (11 hurricanes, 5 major hurricanes) and 1996 (9 hurricanes, 6 major) seasons. If the thermohaline circulation has truly changed, we would expect the active phase to last through the first decade of the next century. A particulary ominous aspect of this prediction is that the increase in activity appears most clearly as an increase in devastating major hurricane landfalls from one every other year to one every year.
Duration: 1981 through the present.
Goldenberg, S. B., L. J. Shapiro, and C. W. Landsea, 1997: Are we seeing a long-term upturn in Atlantic Basin major hurricane activity related to decadal-scale SST fluctuations? Preprints, Seventh Conference on Climate Variations, Long Beach CA, 2-7 February 1997, American Meteorological Society, 305-310.
HURRICANES, TYPHOONS AND TROPICAL CYCLONES FREQUENTLY ASKED QUESTIONS (FAQ)
TROPICAL CYCLONE PUBLIC AWARENESS PROGRAMS: PREPARING FOR THE TWENTY-FIRST CENTURY
SEASONAL FORECASTING OF TROPICAL CYCLONES, TROPICAL RAINFALL AND THE EL NINO-SOUTHERN OSCILLATION
CLIMATE VARIABILITY OF TROPICAL CYCLONES AROUND THE WORLD