Cyclone Nargis Storm Surge Flooding in Myanmar's Ayeyarwady River Delta

Abstract

Tropical cyclones develop in the north Indian Ocean from 55 to 90°E and 5 to 20°N (Webster et al. 2005). The Joint Typhoon Warning Center (JTWC) maintains a “best-track” database for cyclones in the Indian Ocean in the time span of 1945-2007. The Bay of Bengal tropical cyclone center tracks in the database are shown in Fig. 1. Only track information is available prior to 1975. From 1975 to 1979, maximum wind velocity is not available for all cyclones or is only available for partial cyclone tracks. Since 1979, maximum wind velocity is available for all storms.

There are two cyclone seasons in the north Indian Ocean, namely, the pre-monsoon (May) and post-monsoon (October and November). Some cyclones form in the transitional months of June and September. More cyclones form in the Bay of Bengal than in the Arabian Sea based on a respective frequency ratio of approximately 4:1 (Singh et al. 2001). Intense cyclones have been extremely rare over the Arabian Sea with the exception of Gonu in 2007 (Blount et al. 2009; Fritz et al. 2009). Similarly, there is no tropical cyclone track in the JTWC database making a direct landfall at the Ayeyarwady River delta in the Union of Myanmar. In 2006, category 4 cyclone Mala impacted the Gwa coastline roughly 150 km north of the Nargis track.

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