The Odisha-Andhra coastal zone was recently subjected to the impact of Cyclone Titli. This is the third substantial cyclonic event which has struck this region within the last five years—with each occurring in October. The other two cyclones were referred to as Phailin and Hudhud respectively. Name of Cyclone Titli was given by Pakistan.
Cyclones in Bay of Bengal and Arabian Sea
Both the Bay of Bengal and the Arabian Sea experience cyclonic events. However, it’s crucial to point out that the frequency and intensity of these events are significantly higher in the Bay of Bengal. In fact, nearly 58% of cyclones formed in the Bay of Bengal reach the coast, compared to a mere 25% in the Arabian Sea.
Spatial & Temporal Distribution of Cyclones
Cyclones such as Titli, Phailin (2013), and Hudhud (2014) tend to strike in October due to the low wind shear conditions prevalent during this period. Wind shear refers to differences in wind speeds and directions at different levels. The likelihood of cyclones increases during times when wind shear is low, and surface sea temperatures are above 26°C. Cyclones are rare during the monsoon season due to the high wind shear.
Factors Favoring Cyclonic Formation in the Bay of Bengal
Given that sea surface temperatures and humidity have a direct correlation with cyclone formation, the Bay of Bengal experiences more frequent cyclonic action. It benefits from high rainfall, and slow winds around it keep the temperatures relatively high—around 28 degrees throughout the year. Warm air currents boost the surface temperature, facilitating cyclone formation. Also, an inflow of fresh water from the Ganga and Brahmaputra rivers keeps refreshing the Bay’s surface water. This prevents mixing of warm surface water with cooler water below, creating an ideal environment for cyclone initiation.
Contrasting Conditions in the Arabian Sea
The Arabian Sea, on the contrary, experiences stronger winds that help dissipate heat. With no substantial source of fresh water, warm water mixes with cool water, thus reducing surface temperature which is unfavorable for cyclone formation.
Geographical Influence on Cyclone Formation
Due to the absence of a large landmass between the Bay of Bengal and the Pacific Ocean, cyclonic winds easily enter the Bay of Bengal. Once there, these winds encounter the Himalayas and Western Ghats, losing their strength, or getting trapped, but never reaching the Arabian Sea.
Prediction and Evacuation Challenges
Cyclone prediction poses a significant challenge due to budgetary and meteorological constraints. While countries like the US use dedicated aircraft to fly directly into cyclone clouds to gather data, India largely relies on satellite images. This limits the available data to a top view, which reveals little about the moisture content or intensity of the cyclone. Detailed information is often available only when the cyclone is 300-400 km from the coast, leaving minimal preparation time.
Evacuation also has its own challenges. There are three types of evacuation protocols followed – preventive evacuation, shelter-in-place evacuation, and vertical evacuation. Preventive evacuation involves evacuating the entire impact area, but this is rarely feasible in India due to poor roads and inadequate public transport. Shelter-in-place evacuation involves fortifying existing structures, requiring considerable financial resources. Vertical evacuation directs people to specially designed buildings within the impact area, a strategy largely employed during Cyclone Titli.