Cyclone Savannah
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Cyclone Savannah was a strong
tropical cyclone A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
that brought significant impacts to
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
and
Bali Bali () is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller neighbouring islands, notably Nusa Penida, Nusa Lembongan, and Nu ...
and minor impacts to Christmas Island and the Cocos (Keeling) Islands during March 2019. It was the sixteenth tropical low, sixth tropical cyclone and third severe tropical cyclone of the
2018–19 Australian region cyclone season The 2018–19 Australian region cyclone season was an average season that saw the formation of 11 tropical cyclones, six of which intensified further to become severe tropical cyclones. The season officially began on 1 November 2018 and concluded ...
. Savannah developed from a tropical low that formed well to the east of Christmas Island on 8 March. The system was slow to develop initially, but reached tropical cyclone intensity on 13 March after adopting a southwesterly track. Savannah underwent rapid intensification and reached peak intensity on 17 March as a Category 4 severe tropical cyclone on the Australian scale. Ten-minute sustained winds were estimated as , with a central
barometric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...
of 951 
hPa HPA may refer to: Organizations * Harry Potter Alliance, a charity * Halifax Port Authority, Canada * Hamburg Port Authority, Germany * Hawaii Preparatory Academy, a school in Hawaii, US * Health Protection Agency, UK * Heerespersonalamt, the Ger ...
(28.08 
inHg Inch of mercury (inHg and ″Hg) is a non- SI unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States. It is the pressure exerted by a column of mercury in heigh ...
). One-minute sustained winds reached at this time, equivalent to a Category 3 major hurricane on the Saffir–Simpson hurricane wind scale. Weakening commenced soon afterwards, and responsibility for the system passed from the Australian Bureau of Meteorology to
Météo-France Météo-France is the French national meteorological service. Organisation The organisation was established by decree in June 1993 and is a department of the Ministry of Transportation. It is headquartered in Paris but many domestic operatio ...
. As it moved into the new region, Savannah became the eighth of a record-breaking ten intense tropical cyclones in the 2018–19 South-West Indian Ocean cyclone season. Savannah was downgraded to a tropical depression on 20 March, and its remnants dissipated in the central
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
on 24 March. Savannah brought significant impacts to Java and Bali early in its lifetime. Prolonged heavy rainfall and river level rise led to widespread flooding and
landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
s throughout the region. Floodwaters impacted scores of villages, causing damage to thousands of homes, submerging thousands of
hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is a ...
s of agricultural land and cutting off access to key infrastructure and services. Thousands of families were affected during the event, with evacuations occurring both before and after the flooding. According to local media reports, the total damage and economic losses caused by the disaster exceeded Rp106 billion (US$7.5 million). Ten people were reported to have died during the event, making Savannah the deadliest tropical cyclone in the Australian region since Tropical Cyclone Cempaka in 2017. News reports also indicate that at least five people were injured and that one person went missing during the disaster.


Meteorological history

During early March, a moderate strength pulse of the Madden–Julian oscillation tracked eastwards across the tropical
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
and into the
Maritime Continent Maritime Continent is the name given primarily by meteorologists and oceanographers to the region of Southeast Asia which comprises, amongst other countries, Indonesia, Philippines and Papua New Guinea. Located between the Indian and Pacific Ocean ...
. The pulse brought with it weak
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
al conditions to the north of Australia, as well as an atmospheric environment that was favourable for tropical cyclogenesis. On 8 March, the
Australian Bureau of Meteorology Australian(s) may refer to: Australia * Australia, a country * Australians, citizens of the Commonwealth of Australia ** European Australians ** Anglo-Celtic Australians, Australians descended principally from British colonists ** Aboriginal Aus ...
(BOM) noted the formation of a weak tropical low (identifier 17U) within a monsoon trough stretching from
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
to the
Solomon Islands Solomon Islands is an island country consisting of six major islands and over 900 smaller islands in Oceania, to the east of Papua New Guinea and north-west of Vanuatu. It has a land area of , and a population of approx. 700,000. Its capita ...
—one of several tropical lows that would develop within this trough. Located south of
Bali Bali () is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller neighbouring islands, notably Nusa Penida, Nusa Lembongan, and Nu ...
,
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
, and approximately east of Christmas Island, the nascent tropical low began moving slowly westwards. Tracking roughly parallel to the southern coastline of Java, the system passed just to the south of Christmas Island at 06:00  UTC on 11 March, before turning to the northwest. The tropical low executed a poleward turn on 12 March, assuming a course to the southwest by the following day. Tracking away from Indonesia, the storm began to strengthen in a generally favourable environment. The BOM upgraded the system to a Category 1 tropical cyclone on the Australian scale at 18:00 UTC on 13 March as it was approaching the Cocos (Keeling) Islands, and gave it the name Savannah. Six hours later, the United States'
Joint Typhoon Warning Center The Joint typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force command in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North-West Pacific Ocean, South P ...
(JTWC) indicated that the system had reached tropical storm strength on the Saffir-Simpson hurricane wind scale. Intensification continued as Savannah passed approximately to the west of the Cocos (Keeling) Islands, and the system reached Category 2 late on 14 March. Savannah became a Category 3 severe tropical cyclone the following day, and adopted a track to the west-southwest under the influence of a high-pressure
ridge A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...
in the mid-
troposphere The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From ...
further to the south. The storm began to strengthen quickly on 16 March, reaching peak intensity as a Category 4 severe tropical cyclone on the Australian scale at 06:00 UTC the following day, making it the then-strongest storm of the
2018–19 Australian region cyclone season The 2018–19 Australian region cyclone season was an average season that saw the formation of 11 tropical cyclones, six of which intensified further to become severe tropical cyclones. The season officially began on 1 November 2018 and concluded ...
. The BOM estimated ten-minute sustained winds to be at , gusting to , with a central
barometric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...
of 951 
hPa HPA may refer to: Organizations * Harry Potter Alliance, a charity * Halifax Port Authority, Canada * Hamburg Port Authority, Germany * Hawaii Preparatory Academy, a school in Hawaii, US * Health Protection Agency, UK * Heerespersonalamt, the Ger ...
(28.08 
inHg Inch of mercury (inHg and ″Hg) is a non- SI unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States. It is the pressure exerted by a column of mercury in heigh ...
). The JTWC analysed the storm to be producing one-minute sustained winds of , making the system equivalent to a Category 3 major hurricane on the Saffir-Simpson hurricane wind scale. Savannah soon began to weaken, with ten-minute sustained winds decreasing to twelve hours later. By 00:00 UTC on 18 March, the system tracked over the 90th meridian east and into the South-West Indian Ocean cyclone region, and hence responsibility for the storm transitioned to
Météo-France Météo-France is the French national meteorological service. Organisation The organisation was established by decree in June 1993 and is a department of the Ministry of Transportation. It is headquartered in Paris but many domestic operatio ...
(MFR) at La Réunion. According to the scale used by MFR, Savannah was reclassified as a tropical cyclone. Immediately upon entering the region, increasing westerly vertical wind shear allowed dry air to become entrained in the storm's circulation. A rapid weakening trend ensued, despite the warm
sea surface temperature Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air mass ...
s in the vicinity. The system's deep convection proceeded to unravel, leaving the low-level circulation centre exposed, and ten-minute sustained winds decreased to by 00:00 UTC on 19 March. As the convective structure weakened further, Savannah was downgraded to a
gale-force The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. History The scale was devised in 1805 by the Irish hydrographer Francis Beaufort ...
remnant tropical depression at 06:00 UTC on 20 March. The system turned briefly east-southeastwards before adopting a track towards the west-northwest on 21 March. The JTWC downgraded Savannah below tropical storm status at 12:00 UTC that day. Ex-Tropical Cyclone Savannah was last mentioned by MFR on 23 March, and dissipated by 12:00 UTC the next day in the central Indian Ocean.


Impacts


Indonesia

The Indonesian islands of Java and Bali were significantly affected by Savannah's precursor tropical low during the first half of March. Very heavy rainfall occurred across large parts of the islands as the tropical low tracked westwards, causing rapid river level rise, flooding and many
landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
s. A total of ten people died during the disaster, making Savannah the deadliest tropical cyclone in the Australian region since Tropical Cyclone Cempaka, which killed at least 41 people in Java in November 2017. The Indonesian Agency for Meteorology, Climatology and Geophysics indicated that of precipitation fell in parts of
Yogyakarta Yogyakarta (; jv, ꦔꦪꦺꦴꦒꦾꦏꦂꦠ ; pey, Jogjakarta) is the capital city of Special Region of Yogyakarta in Indonesia, in the south-central part of the island of Java. As the only Indonesian royal city still ruled by a monarchy, ...
during 17 March. The regency of Bantul, located downstream from six major rivers, as well as the neighbouring Purworejo Regency, experienced widespread flooding with depths of up to . More than 5,000 residents were forced to evacuate, and access to electricity to was cut by the floodwaters. Numerous landslides in Bantul were also triggered by the extreme rainfall, causing damage and hampering rescue and evacuation efforts. One landslide in Bantul's
Imogiri Imogiri (ꦲꦶꦩꦒꦶꦫꦶ in Javanese script or ''Imagiri'' in standard Javanese spelling) is a royal graveyard complex in Yogyakarta, in south-central Java, Indonesia, as well as a subdistrict under the administration of Bantul Regency. Im ...
district destroyed two houses at the bottom of a cliff, killing three people, and leaving one more missing. Another person was later swept away by floodwaters, and another was killed when a wall collapsed. The economic losses that occurred in Madiun Regency were the worst in two decades, with damages and losses amounting to more than Rp54 billion (US$3.8 million), and more than 5,700 families affected by the disaster. 5,086 houses were damaged by floodwaters throughout the region, and flooding and landslides destroyed three bridges and covered many roads, impeding transportation. A car crash occurred on a wet road in Madiun, resulting in the death of a five-year-old boy and serious injuries to two adults. 497 
hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is a ...
s (1230 
acre The acre is a unit of land area used in the imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imp ...
s) of rice fields were submerged, causing crops to fail and farmers to harvest early to prevent further damage. Significant livestock losses also occurred, including cows, goats and more than 4,000 chickens. In the nearby village of Klumutan, inundation of up to in depth damaged hundreds of houses. Two residents in a village in Madiun died of illness during the event, but were unable to be buried initially due to the flooding of the local cemetery. Further damage and agricultural losses occurred in the regencies of
Ngawi Ngawi may refer to: * Ngawi Regency, an administrative division of Indonesia * Ngawi (city), capital of Ngawi Regency * Ngawi railway station, a station of Paron District, Ngawi Regency * Ngawi, New Zealand, a village in New Zealand See also * ...
,
Tulungagung ) , translit_lang1_info = ꦑꦧꦸꦥꦠꦺꦤ꧀ꦠꦸꦭꦸꦁꦲꦒꦸꦁ , image_skyline = Tulungagung Lead Image.jpg , image_caption = Top: Tulungagung Town Square ( id, Alun-Alun Tulungagung ...
, Bojonegoro and
Ponorogo Ponorogo Regency ( id, Kabupaten Ponorogo; jv, ꦑꦧꦸꦥꦠꦺꦤ꧀ꦦꦤꦫꦒ, translit=Kabupatèn Pånårågå) is a regency (''kabupaten'') of East Java, Indonesia. It is considered the birthplace of Reog Ponorogo, a traditional Indone ...
, totalling more than Rp51 billion (US$3.6 million). In Ngawi, flooding caused approximately of agricultural land to become submerged, and damages and economic losses in that regency alone reached Rp33.2 billion (US$2.35 million). of agricultural land was damaged by flooding in Tulungagung, with crops of rice, melon, chili, long bean and onion affected. In Bojonegoro, flooding of the
Solo River The Solo River (known in Indonesian as Bengawan Solo, with ''Bengawan'' being an Old Javanese word for ''river'', and ''Solo'' derived from the old name for Surakarta) is the longest river in the Indonesian island of Java, it is approximately 600 ...
resulted in widespread impacts. Inundation occurred in 48 villages, affecting more than 1,600 families and causing 50 families to evacuate. A total of of rice fields were submerged by the river water, as well as two kindergartens and three schools. Even after beginning to recede, the level of the Solo River was at above in Karangnongko District, causing the Indonesian National Board for Disaster Management to issue red alerts for riverine flooding for areas further downstream. Flooding in Ponorogo from the Solo River caused five bridges to collapse, and submerged of rice crops. Combined damage in the regencies of
Magetan Magetan Regency is a regency ''(kabupaten)'' of East Java Province, Indonesia. It is an inland regency, and lies in the west of the province, adjoining Central Java Province. It covers an area of 668.84 km2 and had a population of 620,442 at the 2 ...
,
Sukoharjo Sukoharjo Regency is a regency ( id, kabupaten) in the Central Java province in Indonesia. It covers an area of 466.77 km2 and had a population of 824,238 at the 2010 Census and 907,587 at the 2020 Census. Its capital is Sukoharjo, about 10 km so ...
,
Klaten Klaten Regency ( jv, ꦏ꧀ꦭꦛꦺꦤ꧀, Klathèn) is a Regencies of Indonesia, regency in Central Java province in Indonesia. It covers an area of 655.56 km2 and had a population of 1,130,047 at the 2010 Census and 1,260,506 at the 2020 ...
and Bulelung exceeded Rp2 billion (US$140,000). In Magetan, flooding of several rivers caused significant damage to infrastructure, agricultural land and residential areas. 100 people were stranded when nearly 500 houses were flooded in two villages, and damage to roads further inhibited access to affected areas. Losses were sustained on agricultural land, and livestock were killed by the flooding. of rice fields were inundates in Sukoharjo, and flooding of the Gamping River in Klaten submerged of rice fields. In Bulelung in northern Bali, heavy rainfall caused a river that was clogged with garbage and wood to overflow, damaging roads, bridges and electricity infrastructure. A government-subsidised housing complex sustained damage from the flooding, with one house being swept away by the floodwaters. Four tourists were killed and three others were injured in Magelang Regency in central Java on 13 March. The victims had been tubing along the rapids in a river when they were overcome by flash flooding. Several villages in the Pasuruan Regency were affected by flooding, with roads and residential areas becoming inundated. Water levels reaching as high as in Kebrukan Village.


Australia

The Australian territories of Christmas Island and the Cocos (Keeling) Islands experienced minor impacts as Savannah passed nearby. During 11 March, Savannah's precursor tropical low passed just to the south of Christmas Island. At that time, the system had ten-minute sustained winds of only about . As such, no strong winds were recorded on the island. A maximum gust of was observed at 20:05 UTC on 12 March once the system had strengthened further after moving away to the west. A total of of rainfall was recorded on Christmas Island during the seven days from 8–14 March. The system made its closest approach to the Cocos (Keeling) Islands on 14 March, after intensification into a Category 1 tropical cyclone. In preparation for the system's anticipated impacts on the islands, the BOM began issuing tropical cyclone advice products for residents and local authorities at 06:50 UTC on 13 March. Strong sustained winds were experienced on the islands, peaking at gale-force, and a maximum gust of was recorded at 21:35 UTC on 13 March. The wind caused defoliation and vegetation damage on the islands, as well as minor damage to property, but no injuries were reported. Tropical cyclone advice publications were discontinued at 06:50 UTC on 14 March as the system tracked further away from the islands. Over the ten days from 9–18 March, of rainfall was recorded at the
Cocos (Keeling) Islands Airport Cocos (Keeling) Islands Airport ( coa, Lapangan Terbang Pulu Koko (Keeling)) is an airport serving the Cocos (Keeling) Islands, a territory of Australia located in the Indian Ocean. The airport is on West Island, one of the South Keeling I ...
on
West Island The West Island () is the unofficial name given to the cities, towns and boroughs at the western end of the Island of Montreal, in Quebec, Canada. It is generally considered to consist of the Lakeshore municipalities of Dorval, Pointe-Cla ...
, the territory's capital.


Aftermath

Following the significant damage caused by the weather system, the Ponorogo Regency government committed to conduct
dredging Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing da ...
operations to widen the Solo River in order to mitigate future flooding impacts. The government also indicated that they would attempt to quickly rebuild damaged bridges through a special allocation of budget resources for the disaster response. Additionally, residents were urged to refrain from disposing of rubbish in the river, as it was noted that this could exacerbate the risk and impacts of flooding. Significant rubbish pollution resulting in river clogging was also observed in the Bulelung Regency in Bali, where it was regarded as a contributing factor to the flooding. The East Java government allocated Rp100 billion (US$7.1 million) in funding for local governments that declared states of emergency in their local regions due to flooding. The money was intended to cover logistics, equipment, human resources and other necessities for disaster relief and cleanup efforts. Farmers who were affected by the disaster were also able to access Rp6 million (US$420) in compensation from local governments for every hectare (2.5 acres) of damaged agricultural land on their property. With approximately of agricultural land submerged by floodwaters during the disaster, this would have amounted to a total of approximately Rp48 billion (US$3.4 million); however, some farmers were not able to benefit from this assistance as they did not have the necessary agricultural insurance policy provided by the government.


See also

*
Weather of 2019 The following is a list of weather events in 2019. Global conditions 2019 was Earth's second-warmest year on record, which goes back to 1880. It was the 43rd consecutive year of above-average temperatures. The year was 0.95 °C (1.71  ...
*
Tropical cyclones in 2019 During 2019, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 150 systems formed with 102 of these developing further a ...
* Severe Tropical Cyclone Oscar–Itseng (2004)—originated in the Australian region and took a similar track to Savannah * Cyclone Cempaka (2017)—a weak tropical cyclone that killed at least 41 people in Java during November 2017 * Severe Tropical Cyclone Ernie (2017)—took a similar track to Savannah * Intense Tropical Cyclone Kenanga—originated in the Australian region and tracked into the South-West Indian Ocean region


Notes


References


External links


Australian Bureau of MeteorologyMétéo-France at La Réunion
(in French)
Indonesian Agency for Meteorology, Climatology and Geophysics
(in
Indonesian Indonesian is anything of, from, or related to Indonesia, an archipelagic country in Southeast Asia. It may refer to: * Indonesians, citizens of Indonesia ** Native Indonesians, diverse groups of local inhabitants of the archipelago ** Indonesian ...
)
Joint Typhoon Warning CenterOfficial severe weather report on Severe Tropical Cyclone Savannah
{{DEFAULTSORT:Savannah (2019) Tropical cyclones in 2019 2018–19 Australian region cyclone season 2018–19 South-West Indian Ocean cyclone season Tropical cyclones in Indonesia Tropical cyclones in Western Australia Category 4 Australian region cyclones Intense Tropical Cyclones Floods in Indonesia