Category 4 tropical cyclone Batsirai heads for vulnerable Madagascar » Yale Climate Connections

The island nation of Madagascar, already reeling from torrential rains from Tropical Storm Ana on January 22 and a devastating drought in the south of the country, is preparing for the expected landfall of Tropical Cyclone Batsirai on Saturday.

As of 10 a.m. EST Thursday, February 3, Batsirai was a Category 4 storm with winds of 130 mph, tracking west-southwest at 5 mph, according to the Joint Typhoon Warning Center. Radar of Reunion showed that Batsirai had completed an eyewall replacement cycle early Thursday, and that the cyclone was not as organized as it was on Wednesday. Strong wind shear of about 20 knots was interfering with the intensification, and the atmosphere has been dry side, with an average relative humidity of 55%. Sea surface temperatures were a warm 28 degrees Celsius (82°F).

The Joint Typhoon Warning Center and most peak intensity models predict that Batsirai will continue its west-southwest track and gradually weaken, making landfall in east-central Madagascar around 12Z (3 p.m. local) on Saturday, February 5, as a category 2 storm. The coast there is moderately populated and damage from storm surges and wind is likely to be significant. However, the biggest concern for Batsirai will be its widespread rains of 8 to 16 inches which are expected to affect a populated area. The Batsari heavy rain zone may be just south of the country’s most populous city, the capital of Antananarivo, but the country’s third largest city, Antsirabe (pop. 250,000) is likely to receive rains in excess of 10 inches. Unfortunately, the Batsirai rains will especially miss southern Madagascar, where a multi-year drought has 1.6 million people in acute food insecurity.

The Batsirai rains are likely to cause major flooding and major damage to the country, and the storm has the potential to be one of the five costliest disasters in Malagasy history. The damage potential is higher than for previous storms of similar intensity, due to the considerable deforestation Madagascar has experienced over the past 20 years: Madagascar lost 24% of its forest cover between 2000 and 2020, according to globalforestwatch.org. Madagascar is quite mountainous and flood waters flow faster from the deforested mountains, reaching higher heights and causing greater damage.

Figure 1. Precipitation total forecast for Tropical Cyclone Batsirai ending at 12Z on February 8, 2022, from 6Z on February 3, 2022, HWRF model run. Widespread rains of 8 to 16 inches (bright yellow colors) are expected in east-central Madagascar, southeast of the capital Antananarivo. (Image credit: NOAA)

Madagascar already reeling from tropical storm Ana

The Batsirai rains will affect part of Madagascar which is already suffering from the impact of Tropical Storm Ana, the first named storm of the southwest Indian Ocean hurricane season. Ana crossed Madagascar in January as a tropical depression, bringing flooding that killed 48 people and left 71,000 homeless. Ana also killed 18 people in Mozambique and 29 in Malawi, after making landfall in Mozambique as a tropical storm with 60mph winds.

History of the tropical cyclone in Madagascar

Major tropical cyclones have struck Madagascar on average about once every three years since accurate satellite data began in 1997; there have been eight such landfalls between 1997 and 2021. The strongest and deadliest tropical cyclone to hit the island in the satellite era was tropical cyclone Gafilo, which hit the northern tip of Madagascar on March 7, 2004, as a Category 4 storm with winds of 150 mph. Galfilo dumped up to 20 inches of rain, and its winds and torrential rains killed 363 people and caused $375 million in damage (2022 USD), making it the fourth most expensive storm in the history of Madagascar. Prior to landfall, Gafilo’s central pressure of 895 mb was the lowest of any tropical cyclone on record in the southern Indian Ocean.

Six other Category 4 storms hit the island:

Cyclone Enawo, March 7, 2017, winds 150 mph;
Cyclone Givanna, February 13, 2012, winds 130 mph;
Cyclone Hudah, April 2, 2000, winds 130 mph;
Cyclone Gretelle, January 24, 1997, winds 130 mph;
Cyclone Bonita, January 10, 1996, winds 130 mph; and
Cyclone Geralda, February 2, 1994, winds 130 mph.

What’s more March 1927 cyclone that killed up to 500 people was possibly a Cat 4.

Madagascar’s costliest tropical cyclone was Tropical Cyclone Emilie, which made landfall on the island’s east coast on February 2, 1977, as a minimum tropical storm with winds of 40 mph. Emilie dumped torrential rains that caused $1.7 billion in damage (2022 USD).

Figure 2. Category 3 and stronger tropical cyclones making landfall in Madagascar, 1997-2021. Accurate satellite data for the southern Indian Ocean began in 1997. (Image credit: NOAA)

Batsirai rains set to miss Madagascar’s worst drought areas

Southern Madagascar is facing a severe drought-induced food security crisis, with the 2019/20 and 2020/21 rainy seasons bringing only 60% of normal rainfall. The lack of rain in the 24 months from July 2019 to June 2021 was estimated to be one dry event in 135 years, surpassed in severity only by the devastating drought of 1990-92. Drought friends more than 1.6 million people in acute food insecurity.

The Batsirai rains are expected to miss the most drought-ravaged parts of southern Madagascar most of the time, but will contribute to less severe drought conditions on the rest of the island.

Figure 3. Rainfall deviation from average for Southern Africa for the 90 days ending January 30, 2022. Southern Madagascar experienced well below average rainfall. (Image credit: NOAA/CPC)


Climate change is not the main driver of drought in Madagascar

The climatologists who authored a December study with the World Weather Attribution group, “Factors other than climate change are the main drivers of recent food insecurity in southern Madagascar,” found that “the occurrence of low rainfall observed from July 2019 to June 2021 in southern Madagascar has not increased significantly due to human-induced climate change”.

Even where rainfall has not changed, human-caused global warming has been found to make drought more intense in many parts of the world by increasing evaporation and drying out vegetation. However, the authors believe this is not the case for Madagascar. They quoted Kew et al. (2021)who found that in arid and semi-arid regions of East Africa, climate change-induced temperature increases do not appear to lead to significant increases in the likelihood of experiencing exceptional moisture deficits of the soil (and therefore to more intense droughts which dry out vegetation and harm crops).

The authors of World Weather Attribution also summarized recent climate modeling research, which suggests that “future warming during the 21st century could lead to small to moderate increases in rainy season precipitation in southern Madagascar, while the second half of the dry season (August-October) is expected to become drier and longer.

History of tropical cyclones in the southern Indian Ocean

NOAA’s Hurricane History Database lists 18 tropical cyclones in the southern Indian Ocean that have reached Category 5 since 1989. Since accurate satellite recording began in 1997, 14 storms Cat 5 events occurred in the southern Indian Ocean, an average of about one Cat 5 every two years.

The strongest of these storms, Tropical Cyclone Fantala in 2016, peaked with maximum sustained winds of 180 mph and a central pressure of 907 mb pressure. Fantala did not make landfall, although its eyewall affected Farquhar Atoll when the storm was Category 5. Fantala is also the all-time intensity record holder for the entire storm. Indian Ocean, as it leads the northern Indian Ocean record holder, Tropical Cyclone Fani of May 2019 (one-minute peak winds of 175 mph). Note, however, that some consider Tropical Cyclone Monica of 2006 (winds of 180 mph) tied as the strongest Indian Ocean basin storm on record. Definitions vary at the Indian Ocean boundary, however, and Monica peaked north of Australia in the Arafura Sea, which is considered by several sources, including the CIA World Factbookto be part of the Western Pacific Ocean, not the Indian Ocean.

No southern Indian Ocean tropical cyclone has ever been recorded to make landfall at Category 5 strength. At least 17 have made landfall at Category 4 strength: two in Mozambique, seven in Madagascar and eight in Australia western.

The most recent Cat 5 in the basin was Faraji (winds 160 mph, central pressure 925 mb) on February 8, 2021.

Bob Henson contributed to this post.

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