Effects of La Niña on Cyclone Tracks in the Western North Pacific
Nguyen Huu NinhCenter for Environment Research, Education, and Development
Hanoi, Vietnam
cered@netnam.org.vn
This contains cyclone tracks and key characteristics (maximum wind speed, central pressure, etc.) of all recorded tropical cyclones for the western North Pacific during the twentieth century. Data quality for recent decades is considered good, although some information is missing from this data set for the East Sea storms (particularly from the mid-1970s to the mid-1980s). We selected ten La Niña and ten El Niño events and plotted the cyclone tracks for each month during those years. The overall results are not sensitive to the number of events selected. The major impact appears in the months of October and November. During these months, the number of typhoons approaching the coast of Vietnam is twice as great during La Niña, as during El Niño years.
Conclusion
During La Niña events, there are more storms generated in the western part of the central North Pacific and fewer storms curve northward. During these years, conditions for typhoon formation are more favorable in the western Pacific and, combined with atmospheric circulation changes, this strengthens the tracks toward Vietnam. This variability has serious implications for the well-being of the Vietnamese people, because typhoon impacts are a major cause of loss of life and economic damage.