Somali Piracy and the Monsoon

Abstract

Abstract Analysis of the weather and ocean conditions during recent pirate attacks in the Indian Ocean region suggests that the transition of the summer monsoon limits maritime piracy. A comparison of all known pirate attacks in the region in 2010–11 with surface observations from Socotra and the Somali jet index during the same period indicates that pirates attacking from skiffs are thwarted when winds blow in excess of 9 m s−1. The wind speeds and sea states encountered by pirates during individual attacks were reconstructed using satellite altimetry data for 2010–11. Mean daily wind speeds of up to 20 m s−1 during the two boreal summers resulted in consistently rough seas across the Arabian Sea and Indian Ocean. Surface wind speeds during pirate attacks were generally low (less than 8 m s−1), and once wind speeds exceeded 9 m s−1 no successful attacks occurred. The majority (94%) of pirate attacks took place in waves of sea state 4 or less (wave heights below 2.5 m), with pirates rarely attacking after the rough seas of the summer monsoon evolved. Wind speeds and wave heights during the winter monsoon, premonsoon [March–May (MAM)], and postmonsoon [September–November (SON)] seasons were not a deterrent for pirates operating in the Indian Ocean region.