‘Coastal flooding is major threat after cyclone’
In an email interview with Hindustan Times, Jonathan E Martin, professor of atmospheric and oceanic sciences, University of Wisconsin–Madison, USA, spoke about the impact of Cyclone Nisarga over Mumbai, which is expected to make landfall 19 km south of the city on Wednesday. Martin has carried out extensive research for almost 30 years on the evolution of cyclones across the world.
Will Cyclone Nisarga cause severe damage to Mumbai’s infrastructure?
Cyclone Nisarga is likely to develop into a major tropical storm and may possess sustained winds of 35 mph (56-60 kmph) over Mumbai on Wednesday. Such winds can damage tall buildings, but our experience in the US shows that such damage is often not drastic. We suffer much more substantial damage with hurricane-force winds (at or above 120 kmph). Nevertheless, winds will be destructive to structures in a major city like Mumbai.
Has Mumbai ever witnessed a cyclone landfall in history?
This storm may be the first tropical cyclone to strike Mumbai or move very close to the city in 129 years. However, there are stray reports of a cyclone landfall near Mumbai in 1948 and one that was quite close in 2009.
What are some of the most critical measures to be taken while tackling intense cyclones?
Coastal flooding is a major threat from a hurricane landfall. The biggest errors in the past have involved lack of adequate evacuation plans which often traps large numbers of people in desperate situations during flooding. The impact of flooding on the most impoverished areas of the Mumbai Metropolitan Region needs to be the primary response. Providing adequate shelter for those who are displaced by such floods is very important for recovery.
Are pre-monsoon and post-monsoon cyclones increasing in the Arabian Sea?
Cyclones preferentially form in the eastern portion of the Arabian Sea as opposed to the western portion as the waters are much warmer in the east and warm sea surface temperature is a key ingredient for cyclone formation. Considering storms that eventually affect the Arabian Peninsula, there is a slight increase in their frequency over the last 40 years (two in the year 1980, six in 1990, five in 2000 and 12 in 2010) but this trend needs to be further studied.
Are tropical storms intensifying much faster which climate models are failing to identify?
Rising sea surface temperatures encourage more frequent and more intense tropical cyclone development. Modern numerical forecast models including those used by the Indian Meteorological Department is generally quite good at tropical cyclone forecasting. Some developments are missed by these models, but since the storms have life cycles of over a week, even if the models miss their initial development they catch on during the lifecycle.