Cyclone likely to form over Bay of Bengal in few days, rain alert for Andhra Pradesh, Odisha: IMD

A low pressure area over the eastcentral and adjoining southeast Bay of Bengal is likely to intensify into a cyclonic storm in a few days, the India Meteorological Department said on Friday, adding that the system is expected to affect coastal Andhra Pradesh and parts of Odisha.

The low-pressure area is likely to intensify into a depression on October 24, then into a deep depression on October 25 and a cyclonic storm over the westcentral Bay of Bengal by the morning of October 26, Monday, according to an IMD post on X on Friday.

The system is likely to move west-northwestwards towards the North Andhra Pradesh and adjoining South Odisha coasts over the subsequent two days, the IMD said.

In rainfall warnings, the IMD projected extremely heavy to heavy rainfall for coastal Andhra Pradesh and Odisha between October 27 and 29.

According to the roster that lists names of cyclonic storms, the next cyclone that forms in the North Indian Ocean will be named Arnab.

The name Arnab (which means "ocean" in Bengali) was contributed by Bangladesh to the regional tropical cyclone naming list maintained by the World Meteorological Organization (WMO) and the IMD.

A weather system last month also triggered cyclone watch but ended up not intensifying into a cyclonic storm. It, however, crossed Andhra Pradesh-Odisha coast as a deep depression and brought heavy rain. The system had intensified into a deep depression over westcentral and adjoining northwest Bay of Bengal on September 23.

How are depressions, cyclones classified?

According to IMD website, the weather department classifies low-pressure systems based on their intensity, using pressure patterns over land and maximum sustained wind speed over the sea. A system is classified as a low-pressure area when it has one closed isobar, while a depression has two and a deep depression has three. A system with four or more closed isobars is classified as a cyclonic storm.

Based on wind speed, a system with maximum sustained three-minute surface winds of 17-27 knots (31-50 kmph) is called a depression, while 28-33 knots (52-61 kmph) is classified as a deep depression. Once maximum sustained winds reach 34 knots (63 kmph) or more, the system is classified as a cyclonic storm. Thus, a low-pressure area does not automatically mean a cyclone; it must intensify and cross the prescribed thresholds to be classified as one.