Cyclones get stronger, moving slower


Palash, a PhD researcher in meteorology and climate at the University of Saskatchewan in Canada, discusses the impact of cyclones, the role of the Bangladesh Meteorological Department (BMD), and seasonal patterns of cyclones, among others.

How did BMD perform before Cyclone Sitrang?

Unfortunately, the BMD did very poorly in providing a forecast of Cyclone Sitrang to the people of Bangladesh with sufficient lead time. In fact, BMD gave a forecast on October 22, four days after a low pressure system formed on October 18. Just then, I don’t remember any strength from BMD. BMD’s weaknesses are many, including lack of human resources with at least a degree in meteorology or atmospheric science, absence of a broadcast meteorologist, very outdated forecast communication techniques, poorly managed meteorological instruments (e.g. most radars are non-operational), and limited weather observation stations, etc. The issues listed above must be addressed immediately to ensure effective and efficient weather forecasting.

Is there a possibility of another cyclone in December?

In the Bay of Bengal, there are two hurricane seasons per year. The first season runs from April to June and the second from October to December. It should be noted that cyclones rarely form in the northern Bay of Bengal before the third week of October, as the monsoon circulation does not recede until after October 15. Additionally, cyclones do not hit the northern Bay of Bengal after the second week of December because the sea surface temperature becomes too cold to support the development and maintenance of the Cyclone. Therefore, a cyclone forming during the first two weeks of December is possible, but the chances of a cyclone developing in December are very low. Instead of December, the probability of a cyclone developing in the last ten days of November is relatively high.


Have cyclones occurred more frequently in recent years due to climate change?

Scientists need observational data on cyclones for 100 to 200 years to identify a statistically significant trend in the frequency of cyclones in the world’s oceans. Unfortunately, the lack of high-quality, long-duration cyclone datasets prevents scientists from establishing a relationship between cyclone frequency and climate change. Instead of cyclone frequency, scientists found strong evidence of the impact of global warming on the strength of cyclones, the speed cyclones move (translational speed), and the amount of precipitation. Scientists have found that anthropogenic warming of the atmosphere has made cyclones stronger in recent decades. In addition, cyclones take longer to make landfall. Cyclones have moved slower in recent decades compared to previous decades. Since cyclones take longer to make landfall, cyclones in recent decades have produced more precipitation than before.

What will happen in the next 10 to 20 years in terms of extreme weather events like cyclones, flash floods, heavy rains and droughts?

Most tropical cyclone experts agree that in general, people will witness stronger cyclones more frequently, producing a massive amount of precipitation and causing catastrophic damage to lives and property. Due to global warming, the atmosphere retains more water vapor than 30 years ago. Thus, thunderstorms or cyclones in total produce higher precipitation than before. According to a report by the Intergovernmental Panel on Climate Change (IPCC), wetlands will get wetter and dry areas will get drier. This means that humid places like Bangladesh will receive more rainfall in the future, and dry regions like sub-Saharan countries (Mali, Sudan, Libya, etc.) will become drier.


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