A tropical low was analysed to the southwest of Sumatra from 16 April and intensified to cyclone Hamish by the afternoon of 20 April. Hamish moved to the southwest but approached a zone of high vertical wind shear to the south. The influence of the shear caused rapid weakening of the cyclone during the night of the 21st April.
For more details see the TC Hamish Report (pdf)
Track and intensity
All times in WST - subtract 8 hours to convert to UTC.