Six weeks after Intense Tropical Cyclone Idai caused 600 fatalities in Mozambique, a second storm, Cyclone Kenneth, made landfall in northern Mozambique on 25 April 2019 (OCHA, 2019). Cyclone Kenneth was ranked as a Category 4 storm on the Saffir-Simpson scale, with gust wind speeds reaching a maximum of 270kph and average wind speeds of 185kph (World Meteorological Organization, 2019).
Figure 1: The areas highlighted in blue represent the extent of flooding due to Cyclone Kenneth. The flood extent data was processed by Copernicus using Sentinel satellite data. (Data source: Copernicus Emergency Management Service)
Cyclone Kenneth is the strongest cyclone to make landfall on the African continent since records began (OCHA, 2019). This latest weather system was predicted to result in twice as much rainfall as compared to Tropical Cyclone Idai (BBC, 2019), which caused 900 fatalities and approximately USD $2 billion of damage based on the impact to infrastructure (Reinsurance News, 2019). Further information on Tropical Cyclone Idai can be found in JBA’s previous report, available here.
Summary of Cyclone Kenneth
Figure 2: Rainfall accumulation (mm) for north-east Mozambique and Comoros from 25-30 April 2019, based on daily precipitation data collected by NASA Precipitation Measurement Mission. (Data source: NASA PPM, 2019)
Cyclone Kenneth formed in the Mozambique Channel, near northern Madagascar and on the east of Aldabra Atoll, on 23 April 2019. It hit Comoros on 24 April 2019, causing seven reported deaths and 200 serious injuries, with more than 20,000 people being displaced (UNICEF, 2019). More than 80% of agricultural farmland was destroyed, significantly threatening the primary economy and food security in Comoros (UNICEF, 2019). Based on reported figures, 3,818 houses were destroyed and an additional 7,013 houses and 608 schools were damaged by the cyclone (UNICEF, 2019).
The cyclone travelled further west and made landfall in northern Mozambique between the districts of Macomia and Mocimboa da Praia in Cabo Delgado province (OCHA, 2019). It made landfall towards the end of the wet season in Mozambique, when water levels in rivers were already high and the ground saturated. The cyclone was slow-moving and so the additional rainfall due to the cyclone exacerbated flooding in areas already vulnerable to flood risk (OCHA, 2019). Quisanga, Macomia and Ibo districts, of Cabo Delgado state, were the worst affected based on government reports. As Figure 2 illustrates, these districts received high amounts of rainfall over a five-day period between 25 to 30 April 2019. Pemba, the regional capital of Cabo Delgado, recorded total rainfall of 168.7mm within 24 hours between 27 and 28 April 2019 and 254.7mm between 28 and 29 April (World Meteorological Organization, 2019).
Figure 3: Rainfall accumulation for Mozambique due to Tropical Cyclone Idai from 13-18 March 2019 (left) and rainfall totals from Cyclone Kenneth between 20-25 April 2019 (right).
Cabo Delgado province is not as densely populated or low-lying as the port city of Beira, which was particularly affected by Tropical Cyclone Idai. This is likely to mean that economic losses for Cyclone Kenneth will be lower than for Idai. In addition, the area affected by Tropical Cyclone Idai has several rivers converging together before flowing into the Mozambique Channel, making it more susceptible to large scale flooding (CNN, 2019). Figure 3 illustrates the rainfall distribution for Cyclones Idai and Kenneth respectively. Based on NASA Satellite data, the maximum total five-day rainfall observed near Beira city as a result of Cyclone Idai was approximately 600mm (recorded between 13-18 March 2019) (Figure 3). This was not exceeded by Cyclone Kenneth, with observed rainfall more in the range of 230-250mm near the Quisanga and Ibo districts from 20-25 April 2019 (Figure 3).
Impact of climate change on tropical cyclones
The World Meteorological Organization highlights that Mozambique has not experienced two high intensity cyclones within the same season before, based on historical records (World Meteorological Organization, 2019).
There are several factors which can influence the frequency and intensity of cyclones formed. Sea surface temperature is one important factor in the formation of storms with high intensity. Warmer sea surface temperatures mean that more energy is available for storms to develop as they begin to form further away from the equator (McGrath, 2019). In addition to climate change, there are other local weather mechanisms such as the El Nino Southern Oscillation, Indian Ocean Dipole and the Madden-Julian Oscillation which can result in higher sea surface temperature in the southern Indian Ocean (Fitchett, 2019). The increase in sea surface temperatures increases the range at which cyclones can form. Cyclone Kenneth made history as the northernmost cyclone to affect Mozambique (Fitchett, 2019).
Sea surface temperature is not the only factor contributing to cyclone formation. In general, six conditions must be present for the formation of hurricanes, cyclones and typhoons: high sea surface temperature, sufficient Coriolis force, low vertical wind shear, high humidity, pre-existing disturbance and atmospheric instability (NOAA Hurricane Research Division, 2019). These weather events were rare in the past as it was unlikely that the conditions would coincide in space and time. However, due to climate change these conditions occur more frequently and so it is likely that the frequency of large storms will increase, not only in the Southern Indian Ocean basin (McGrath, 2019).
Recent research published in the journal Nature examines how future changes in air and ocean temperatures will impact tropical cyclones, in terms of rainfall and wind-speed. In comparison with pre-industrial conditions, climate change has already enhanced the mean and maximum rainfall for recent hurricane events. For instance, climate change increased the mean and extreme rainfall for Hurricanes Katrina, Irma and Maria, but there is no evidence to support that climate change also increased the hurricane events’ wind-speed intensity (Patricola and Wehner, 2018).
The study concludes that rainfall from tropical cyclones is likely to increase by 33%, while wind speeds may increase by 25 knots (46kph), if global average temperatures increase by 3-4°C (Milman, 2018). To illustrate further, the intensity of a storm comparable to the 2004 storm that hit Madagascar, causing 300 deaths, would increase by 40% if global temperatures were to rise by 3°C this century.
Flood losses based on historical events and current insurance penetration rates
The wet season in Mozambique is typically from December to April. On average, 1.5 cyclones hit Mozambique during the annual cyclone season in the southern Indian Basin (Leahy, 2019). Floods and cyclones contribute to a significant proportion of economic loss caused by natural catastrophes. 45.6% of the fatalities occurred in a natural catastrophe were related to floods. Storms, cyclones and floods caused 97% of all reported economic losses for catastrophe events between 1990 and 2014 in Mozambique (PreventionWeb, 2019).
Some of the strongest cyclones in the southern hemisphere include Tropical Cyclone Idai (2019), Cyclone Eline (2000) and Cyclone Gafilo (2004) (Miller and Adebayo, 2019). Cyclone Kenneth is the strongest cyclone to make landfall in Mozambique in recorded history, which was preceded by Tropical Cyclone Idai six weeks earlier (CNN, 2019). The economic losses incurred by Idai are likely to be one of the costliest events in Mozambique’s history, with estimates ranging from USD $656-$773 million (Reuters, 2019) (Table 1). This value represents the direct losses incurred from damaged infrastructure, buildings and losses to agricultural production. Indirect losses from business disruption and decreased productivity are not included in the figure provided by the World Bank. However, the World Bank also estimates that USD $2 billion will be required by the affected districts to aid recovery (African News, 2019).
Table 1: A summary of several historical flood events and economic losses. (Data source: Swiss Re, 2019 and World Bank, 2019)
A significant proportion of the incurred losses are likely to be borne by the individuals, government and humanitarian organisations as insurance penetration rate is fairly low (1.4%) in Mozambique, although it is relatively higher than other countries in the African continent (Swiss Re, 2017) (Figure 4). With climate change projected to increase the intensity of cyclones in the region, it is possible that the country will need to adapt to more severe wind and flood events in the future and it will be interesting to see what role insurance may play in this.
Figure 4: Non-life insurance penetration rates for countries in Africa. (Data source: Swiss Re, 2017)
JBA Risk Management has nationwide return period flood maps available for Mozambique at 30m resolution. For more information, get in touch.
References
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Leahy, S. 2019. Why Cyclone Idai was so destructive. [online] Available at: https://www.nationalgeographic.com/environment/2019/03/why-mozambique-cyclone-idai-was-so-destructive/ [Accessed 7 May 2019].
McGrath, M. 2019. Cyclone Idai: What's the role of climate change?. BBC. [online] Available at: https://www.bbc.com/news/science-environment-47638588 [Accessed 7 May 2019].
Miller, B. and Adebayo, B. 2019. Cyclone Kenneth: Thousands evacuated as Mozambique is hit with the strongest storm in its history. CNN. [online] Available at: https://edition.cnn.com/2019/04/25/africa/cyclone-kenneth-mozambique-evacuation-intl/index.html [Accessed 9 May 2019].
Milman, O. 2018. Climate change is making hurricanes even more destructive, research finds. The Guardian. [online] Available at: https://www.theguardian.com/environment/2018/nov/14/climate-change-hurricanes-study-global-warming [Accessed 7 May 2019].
NOAA Hurricane Research Division. 2019. How do tropical cyclones form? [online] Available at: https://www.aoml.noaa.gov/hrd/tcfaq/A15.html [Accessed 9 May 2019].
OCHA. 2019. Cyclone Idai and Kenneth. [online] Available at: https://www.unocha.org/southern-and-eastern-africa-rosea/mozambique [Accessed 7 May 2019].
Patricola, C. and Wehner, M. 2018. Anthropogenic influences on major tropical cyclone events. Nature. 563(7731), pp.339-346.
PreventionWeb. 2019. Mozambique Disaster & Risk Profile. [online] Available at: https://www.preventionweb.net/countries/moz/data/ [Accessed 29 Mar. 2019].
Swails, B. and Berlinger, J. 2019. Tropical Cyclone Kenneth death toll rises to 38 in Mozambique, officials say. [online] Available at: https://edition.cnn.com/2019/04/29/africa/mozambique-cyclone-kenneth-intl/index.html [Accessed 7 May 2019].
Swiss Re. 2017. Insurance penetration (Non-Life). [online] Available at: http://www.sigma-explorer.com/ [Accessed 7 May 2019].
UNICEF. 2019. UNICEF Comoros Humanitarian Situation Report3 – April 2019. [online] Available at: https://reliefweb.int/sites/reliefweb.int/files/resources/UNICEF%20Comoros%20Humanitarian%20Situation%20Report%20No.%203%20%28Cyclone%20Kenneth%29%20-%20as%20of%2029%20April.pdf [Accessed 7 May 2019].
Wood, C. 2019. World Bank pegs Cyclone Idai economic loss at $2bn. [online] Reinsurance News. Available at: https://www.reinsurancene.ws/world-bank-pegs-cyclone-idai-economic-loss-at-2bn/ [Accessed 7 May 2019].
World Meteorological Organization. 2019. Another unprecedented tropical cyclone and flooding hits Mozambique. [online] Available at: https://public.wmo.int/en/media/news/another-unprecedented-tropical-cyclone-and-flooding-hits-mozambique [Accessed 7 May 2019].