On 21 May 2009, the Joint Typhoon Warning Center reported a Tropical Disturbance had persisted about 950 kilometres (590 mi) to the south of Kolkata, in India and had developed.
During 22 May 2009, the disturbance developed further with a Tropical Cyclone Formation Alert being issued early the next day by the JTWC as the low level circulation center had become stronger and more defined.
Later that day, RSMC New Delhi reported that the deep depression had intensified into a Cyclonic storm and had been named as Aila whilst located about 350 kilometres (220 mi) to the southeast of Sagar Island.
Aila became a severe cyclonic storm at 06UTC on May 25 and made landfall at its peak intensity (60kt, 967hPa) between 08 and 09UTC.
Officials in India evacuated thousands of residents from coastal areas ahead of Cyclone Aila.
In addition, several warning alerts were issued before the cyclone hit Kolkata; however, no alarm bells were rung.
In the Bhola District of Bangladesh, an estimated 500,000 people evacuated to higher areas and shelters as Aila neared landfall.
Tourists were advised to stay in their hotels due to the short amount of time to prepare for the storm.
Resultant Damage Large number of water resources were contaminated by salination Crops were destroyed, parts of the land were waterlogged or effected by salination. Extensive loss of livestock and draught animals 80% of the forest cover as damaged badly along with plantations.
In India, at least 149 people were killed, and hundreds others were left homeless as torrential rains led to flooding.
In northern areas of the state, heavy rains triggered numerous landslides in that killed 22 people and left 6 others missing. At least 50,000 hectares of agricultural land was lost during the storm, costing an estimated Rs. 125 crore (US$26.3 million).
Throughout the state, an estimated 40,000 homes were destroyed and 132,000 others were damaged. At least 350,000 people affected by Aila.
Village after village lay submerged. According to experts, Sunderbans has never been hit by such a destructive storm in the last three decades.
Apart from the human tragedy, the cyclone and subsequent floods has badly affected the mangrove forests of Sunderbans and presumably caused a sizable damage to its animal life by sweeping away a large number of highly endangered Bengal tigers, crocodiles, wild boars and spotted deer.