Global Effects of ENSO

Tropical Cyclone Activity

Introduction

Hurricanes are severe tropical storms that form in the tropical waters of the Atlantic Ocean and the Eastern Pacific. In other oceans, they are known by different names: typhoons (Western North Pacific), tropical cyclones (Indian Ocean and Soutwestern Pacific). Here, we use the term tropical cyclone to refer to all severe tropical storms in general. Tropical cyclones are among most dangerous natural disasters. Their destructive potential is due to their strong winds, flooding caused by strong rainfall, and storm surges in coastal regions.

El Niño-Southern Oscillation (ENSO) is known to affect tropical cyclones in different ways around the globe. ENSO alters the global atmospheric circulation affecting tropical cyclone frequencies by changes in the lower troposphere vorticity sources and the vertical wind shear (differences in wind between upper and lower levels) (Landsea 2000 ). The response of the different basins to ENSO vary, some show changes in the frequency of events, while others have shifts in the initial location of the tropical cyclones (Landsea 2000). There many reasons for these different responses: the relation between time of year of peak tropical cyclone activity to the ENSO annual cycle, the location of the basin in relation to the eastern equatorial Pacific and the climatological characteristics of each basin (Landsea 2000). While the Pacific region tropical cyclone activity can be forced directly by the sea surface temperature changes, the other basins are affected only indirectly through teleconnections (Landsea 2000).

Influence of ENSO on Tropical Cyclones

• North Atlantic Ocean Hurricanes

Links and References

Web Sites with Information and forecasts of Tropical Cyclones

• National Hurricane Center (US)  
• Joint Typhoon Warning Center
• Central Pacific Hurricane Center
• Central Weather Bureau, Taiwan
• Tropical Cyclone Advisory - Japan Metereological Agency
• Cyclone information - Australian Bureau of Metereology
• Hurricane/Tropical Data - Unysis Weather
• Tropical Cyclone Homepage  - NRL Monterey Marine Meteorology Division
• The Tropical Meteorology Project  - Colorado State University
• Atlantic Hurricane Outlook - Climate Prediction Center
• Tropical Cyclones  - Hawaii University
• Tropical Cyclones  - University of Wiscosin-Madison
• West Pacific Tropical Cyclone Prediction  - City University of Hong Kong
• Canadian Hurricane Center
• Tropical Cyclones  - Metereological Office (UK)

General Review of Tropical Cyclones

• Gray, W.M. Hurricanes: Their formation, structure and likely role in the general circulation. In Metereology over the Tropical Oceans, D.B. Shaw, Ed., Royal Metereological Society, p. 155-218 (1979).

A Summary of the Influence of ENSO on Tropical Cyclones

• Landsea, C.W. El Niño/Southern Oscillation and the Seasonal Predictability of Tropical Cyclones. In El Niño and the Southern Oscillation: Multiscale Variability and Global and Regional Impacts, H.F. Diaz and V. Markgraf, Cambridge University Press, p. 149-181 (2000).