Death Toll From Idai Rises Above 800: 3rd Deadliest Southern Hemisphere Cyclone on Record

April 1, 2019, 10:03 AM EDT

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Above: Cyclone Idai as seen at 12Z March 14, 2019, approaching landfall in Mozambique. Image credit: NASA.

The death toll from horrific Cyclone Idai in southeast Africa has risen above 800, making the storm the third deadliest tropical cyclone on record in the Southern Hemisphere. Only Tropical Cyclone Flora of 1973 (1650 killed in Indonesia) and the 1892 Mauritius Cyclone (1200 deaths in Mauritius) were deadlier.

The official death for Idai on Monday morning stood at 826, with 501 dead in Mozambique, 259 in Zimbabwe, 56 in Malawi, 7 in South Africa, and 3 in Madagascar. According to EM-DAT, Idai is the deadliest flood on record for Zimbabwe, exceeding the toll of 251 in January 2017 from Tropical Cyclone Dineo.

The final death toll from Idai will never be known. Media reports detail that many bodies have been buried without being registered with authorities. The bodies of many other victims have been eaten by crocodiles or washed out to sea, and many will never be found.

Africa’s Hurricane Katrina

Tropical Cyclone Idai made landfall on March 14 as a Category 2 storm with 110 mph winds just north of Beira, Mozambique (population 530,000) near the time of high tide, driving a devastating storm surge into the city. The cyclone also caused enormous wind damage, ripping off hundreds of roofs in Mozambique’s fourth largest city. Since the cyclone was large and moving slowly at landfall, near 6 mph, it was a prodigious rainmaker, with satellite-estimated rainfall amounts in excess of 2 feet in portions of central Mozambique. Idai stalled and died over the high terrain of the Zimbabwe-Mozambique border region, bringing heavy rains of over a foot to eastern Zimbabwe. Runoff from these rains submerged huge portions of central Mozambique. One estimate, based on Sentinel-1 data acquired on March 19, indicated that water covered roughly 2,165 square kilometers (835 square miles) of eastern Africa, an area half the size of Rhode Island.

Idai precipitation
Figure 2. Seven-day satellite-estimated rainfall amounts for Idai from March 13 – 20, 2019. Rainfall in excess of 500 mm (19.68”) fell in central Mozambique, with over 250 mm (9.84”) in eastern Zimbabwe. This map does not show the heavy rains in excess of a foot that Idai’s precursor tropical disturbance dumped over northern Mozambique and southern Malawi prior to March 13. Local rainfall amounts can be significantly higher than these satellite estimates. Image credit: NASA Earth Observatory.

The third deadliest Southern Hemisphere tropical cyclone on record

Idai is among the deadliest Southern Hemisphere deadliest tropical cyclones on record. Using data from EM-DAT, the international disaster database, plus other official and unofficial sources, the 826 deaths officially attributed to Idai so far would make it the third deadliest Southern Hemisphere tropical cyclone on record. As is usual for catastrophic storms, there is considerable uncertainty in these numbers:

                   Deadliest Southern Hemisphere Tropical Cyclones
Rank   Deaths   Storm             Location                                               Year

  1.  1650   Unnamed        Flores, Indonesia                                           1973               
  2.  1200   Unnamed        Mauritius                                                        1892
  3.   826    Idai                  Mozambique, Zimbabwe, Malawi                  2019
  4. ~800    Eline                Mozambique, Madagascar, Zimbabwe          2000
  5.   517    Unnamed        French Polynesia                                           1903
  6.   500    Unnamed         Madagascar                                                  1951
  7. ~500    Unnamed        Madagascar                                                   1927
  8.   418    Gafilo              Madagascar                                                   2004
  9.   300+  Unnamed        Madagascar                                                   1959
  10.   300+  Mahina            Australia                                                         1899

Notes: The deadliest tropical cyclone on record for the Southern Hemisphere was a 1973 storm informally named Cyclone Flores, which hit the Indonesian island of Flores. The cyclone is blamed for 1650 deaths, including 1500 fisherman lost at sea. Mozambique’s deadliest cyclone was Eline of 2000, which hit southern Mozambique as a Category 4 storm with 130 mph winds on February 22, 2000. Eline dumped torrential rains on a region that was already suffering severe flooding from over a month of heavy rains, and the combined floods killed over 700 people in Mozambique, according to Meteo-France (thanks go to Philippe Caroff for this link). Eline also killed 12 people in Zimbabwe and 64 in Madagascar, bringing the storm’s total death toll to approximately 800. There is some uncertainty on how many of the deaths in Mozambique can be attributed to the flooding that came before Eline, though.

The January 13, 1903 cyclone that killed 517 people in Tahiti and surrounding islands is well-documented in a detailed history of tropical cyclones in the Pacific, the 2012 book Furious Winds and Parched Islands: Tropical Cyclones (1558–1970) and Drought (1722 – 1987) in the Pacific, by AnaMaria d’Aubert and Patrick D. Nunn. There are also two newspaper accounts (here and here) of the January 13, 1903 cyclone, saying that it brought a 40-foot high wave that inundated Tahiti and neighboring islands, killing as many as 5,000 – 10,000 people. However, another newspaper article mentions that a significant earthquake occurred that day as well, and the extreme wave observed during the cyclone may have been a tsunami from an earthquake. Thanks go to Jeffrey Callaghan for these links.

Idai the 17th deadliest weather disaster in African history

Idai currently ranks seventeenth on the list of deadliest weather disasters in African history. According to EM-DAT, that list is dominated by catastrophic droughts. As usual, there is considerable uncertainty in these numbers:

                                          Deadliest African Weather Disasters
      Deaths           Event               Location                                                          Year

  1. 450,000           Drought           Ethiopia, Sudan                                              1983 – 1985
  2. 100,000           Drought           Ethiopia                                                          1973 – 1978
  3. 100,000           Drought           Mozambique                                                   1981 – 1985
  4.  85,000            Drought           Niger                                                               1910 – 1914
  5.  30,000            Drought           Cabo Verde                                                     1946
  6.  24,000            Drought           Cabo Verde                                                     1920
  7.  20,000            Drought           Cabo Verde                                                     1940 – 1944
  8.  20,000            Drought           Somalia                                                           2010 – 2011
  9.  19,000            Drought           Somalia                                                           1974 - 1976
  10.  11,000            Drought           Cabo Verde                                                     1900
  11.    3,000             Drought          Chad                                                               1981 - 1985
  12.    3,000             Flash flood     Algeria                                                             1927
  13.    2,311             River flood      Somalia                                                           1997
  14.    2,000             Drought          Ethiopia                                                           1965
  15.    1,102             Mudslide        Sierra Leone                                                    2017
  16.       921             River flood     Algeria                                                              2001
  17.       826             TC Idai           Mozambique, Zimbabwe, Malawi                    2019
  18.    ~800             TC Eline          Mozambique, Madagascar, Zimbabwe           2000    
  19.      730             River flood      Morocco                                                          1995
  20.      600             River flood      Egypt                                                               1994
  21.      600             Drought          Somalia                                                           1987

An indirect death toll of thousands more

The aftermath of a major tropical cyclone often results in a huge number of indirect deaths—people who don’t die due to the direct impact of the storm’s winds and floods, but from malnutrition, infectious disease, lack of medicine, and other causes. For example, when Hurricane Maria hit Puerto Rico and the U.S. Virgin Islands in 2017, the storm was blamed for approximately 65 direct deaths. However, multiple studies in the years following the hurricane found that the indirect death toll was in the thousands. NOAA now accepts that the U.S. direct and indirect death toll from Maria is 2971.

The direct death toll for Hurricane Katrina of 2005 is 520 – 822, but one 2007 study that drew on death notices in the New Orleans Times-Picayune estimated that there were 2358 excess deaths in the local area during the months of January - June 2006, compared to the years 2002 - 2004.

In less developed places like Mozambique, the indirect death toll from a catastrophic cyclone is likely to be much higher than for the U.S. Doctors Without Borders is reporting seeing 200 cases of the dreaded water-borne disease cholera per day in Beira, and the first cholera death in the city was reported on Monday. A significant cholera outbreak has the potential to cause large loss of life. Since 1983, Mozambique has suffered nine cholera outbreaks that have killed between 100 and 700 people each, according to EM-DAT. The World Health Organization said 900,000 oral cholera vaccines were expected to arrive Monday and a vaccination campaign will begin later this week.

The influence of climate change

Regular satellite imagery of the Southwest Indian Ocean began in 1998, so we only have about a 30-year data set to study historical trends in tropical cyclones. Since climate change is best studied using datasets of 30 years or longer, this makes it difficult to say specifically how climate change is affecting Southwest Indian Ocean tropical cyclones.

We should expect that Idai’s heavy rains were increased due to climate change, though, since one of the more confident predictions hurricane scientists can make on the future of tropical cyclones in a warmer climate is that they will dump heavier rains due to increased moisture in the atmosphere. We don’t have a specific attribution study on how climate change may have affected Idai’s rains, but a study done for Hurricane Harvey of 2017--Wang et al. (2018), Quantitative attribution of climate effects on Hurricane Harvey's extreme rainfall in Texas--found that warming of the atmosphere and ocean since 1980 could have increased Hurricane Harvey’s extreme precipitation by 13% - 37%.

A key reason for Idai’s extreme destruction was the very slow motion of the cyclone at landfall, 5 – 10 mph. This slow motion allowed the storm to dump prodigious rains. As detailed in our June 2018 post, Observed Slowdown in Tropical Cyclone Motion May Portend More Harvey-Like Rainstorms, a 4% slowdown in the forward speed of tropical cyclones in the Southwest Indian Ocean has been observed in recent decades. It is uncertain if this trend is due to human-caused global warming, but there are good reasons to believe that this could be the case.

Idai’s storm surge was terribly destructive, and was definitely worse because of climate change. Global sea levels are about 8” higher because of human-caused climate change than they were a century ago, and this extra rise allows the storm surge of all tropical cyclones to cause increased destruction.

Probably the most sophisticated study done yet on what the future may hold for tropical cyclones on the Southwest Indian Ocean was a 2018 paper, Projected Response of Tropical Cyclone Intensity and Intensification in a Global Climate Model,  which used a high-resolution global climate model (HiFLOR). The 2018 study predicted a dramatic increase in the global incidence of rapid intensification due to global warming, and a 20% increase in the number of major hurricanes globally in the climate of the late 21st century. For the Southwest Indian Ocean, the model did not predict a significant increase in the number of days Category 3 and stronger cyclones would affect Mozambique, but did for nearby Madagascar and Mauritius.

How to help

The weather is forecast to cooperate with relief efforts in the cyclone-ravaged area this week, with mostly dry weather expected.

The International Federation of Red Cross and Red Crescent Societies, the United Nations, and Save the Children have targeted donation links so you can help provide food, medical supplies, and shelter to victims of Idai in Mozambique. The United Nations says that more than 2.6 million people are in need of immediate assistance.

A spokesperson from the International Medical Corps wrote me to say that they have sent a response team to the disaster zone: “We have a longstanding presence in Zimbabwe, and our team is working to gain access to some of the most devastated areas to identify how best we can help people hurt by this destructive storm. Our experts are deploying to reach affected areas in the region to quickly expand support for health, hygiene and other needs.” Their targeted donation page for the disaster is here.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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Dr. Jeff Masters

Dr. Jeff Masters co-founded Weather Underground in 1995 while working on his Ph.D. in air pollution meteorology at the University of Michigan. He worked for the NOAA Hurricane Hunters from 1986-1990 as a flight meteorologist.

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