Nov. 15 (Bloomberg) -- Indian and Bangladeshi authorities ordered thousands of people to evacuate as Tropical Cyclone Sidr headed across the Bay of Bengal toward the coast with winds of 250 kilometers (156 miles) per hour.

Sidr, a Category 5 storm, was 201 kilometers east-southeast of Kolkata at 11:30 a.m. local time today, according to the latest advisory by the U.S. Navy's Joint Typhoon Warning Center. The storm was moving north at 28 kilometers an hour.

The cyclone is expected to maintain strength as it approaches the coastal border region between India and Bangladesh. Sidr's eye is forecast to make landfall southeast of Kolkata, a city of 14.3 million people formerly known as Calcutta, at about 11 p.m. today, the center said.

Northeastern India and Bangladesh are regularly hit by cyclones that form in the Bay of Bengal, bringing flooding and devastation to local communities. A cyclone that hit near Cox's Bazaar in Bangladesh left 138,000 people dead in 1991, according to the New York Times.

At least one fisherman was killed and about 100 others were listed as missing in the region of Cox's Bazaar after Tropical Cyclone Akash came ashore in May. Sidr is the sixth storm of the north Indian Ocean cyclone season.

Authorities ordered people to evacuate coastal areas near Cox's Bazaar, Mongla and Chittagong and issued the highest alert in sixteen districts, K.H. Massod, director general of disaster management in Bangladesh, said by telephone today.

Warnings Issued

India's cabinet at a meeting at 7 p.m. local time discussed the cyclone as an ``emergency measure'', a government statement said. The Ministry of Home Affairs issued warnings to residents of West Bengal, Orissa and Andaman and Nicobar Islands, the statement said.

``People have been told to move to government shelters and fishermen are being told not to venture into the seas,'' Atanu Purkayastha, relief commissioner in West Bengal state government, said by telephone.

In neighboring Orissa, four coastal districts were put on alert, K.L. Mishra, deputy general manager of the state's disaster management office, said by telephone.

``Food stocks have been rushed to these districts and relief materials, such as blankets and temporary shelters, are being readied,'' Mishra said. About 9,000 people were killed in Orissa when a cyclone hit the state in 1999, he added.

Sidr's winds were gusting to 306 kilometers per hour and waves in the vicinity of the storm's eye were 12 meters (40 feet) high, according to the advisory on the warning center's Web site.

Storm Surge

Hurricane-force winds of 119 kilometers per hour extend as far out as 111 kilometers from Sidr's eye, according to the Navy typhoon center.

Sidr may produce a storm surge of more than 5.5 meters when it comes ashore in one of the most flood-prone areas in the world. The border area of India and Bangladesh is where the deltas of the Ganges and Brahmaputra rivers meet.

In the Indian Ocean, the U.S. Navy uses the term tropical cyclone to describe all large circular weather systems built around an area of low pressure.

That differs from its conventions for the Pacific, where a three-level system is used. Cyclonic storms with winds less than 62 kilometers per hour are classified as tropical depressions, winds between 63 and 118 kilometers per hour are classified as tropical storms and winds of 119 kilometers per hour and greater are typhoons.

In the Atlantic, U.S. meteorologists refer to typhoons as hurricanes and classify them according to the five-tier Saffir- Simpson scale. Category 4 storms have winds of between 210 and 249 kilometers per hour.

-- With reporting by Bibhudatta Pradhan in New Delhi Editors: Johnson (pmt/wdg/jrs/hgc).

To contact the reporters on this story: Jay Shankar in Bangalore at Jshankar1@bloomberg.net; Aaron Sheldrick in Tokyo at asheldrick@bloomberg.net.

Last Updated: November 15, 2007 09:42 EST