Tropical Cyclone Lili was a small and relatively weak off-season

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. Dep ...

that brought moderate impacts to the

Maluku Islands The Maluku Islands (; Indonesian: ''Kepulauan Maluku'') or the Moluccas () are an archipelago in the east of Indonesia. Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located ...

and

East Timor East Timor (), also known as Timor-Leste (), officially the Democratic Republic of Timor-Leste, is an island country in Southeast Asia. It comprises the eastern half of the island of Timor, the exclave of Oecusse on the island's north-we ...

, and mild impacts to other parts of eastern

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 far-northern Australia. It was the latest tropical cyclone to exist in 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 Au ...

's northern tropical cyclone region on record, surpassing Severe Tropical Cyclone Verna of 1977. Lili was the tenth 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 ...

, and the second of which to be named by the

Indonesian Agency for Meteorology, Climatology and Geophysics Meteorology, Climatology, and Geophysical Agency ( id, Badan Meteorologi, Klimatologi, dan Geofisika, abbreviated BMKG) is an Indonesian non-departmental government agency for meteorology, climatology, and geophysics. History Its history began ...

. Lili originated from a tropical low that formed over the

Banda Sea The Banda Sea ( id, Laut Banda, pt, Mar de Banda, tet, Tasi Banda) is one of four seas that surround the Maluku Islands of Indonesia, connected to the Pacific Ocean, but surrounded by hundreds of islands, including Timor, as well as the Halma ...

on 4 May 2019. The system gradually organised as it tracked slowly southwards, and strengthened into a Category 1 tropical cyclone on the

Australian scale Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basins they are located in. Only a few scales of classifications are used officially by the m ...

on 9 May. Lili reached peak intensity later that day, with ten-minute

sustained winds Sustain is a parameter of musical sound in time. Sustain may also refer to: * ''Sustain'' (album), a 2007 album by ska punk band Buck-O-Nine * ''Sustain'' (composition) a 2018 orchestral composition by American composer Andrew Norman * Sustain ...

of and 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 millibar ...

of 997

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 Ge ...

(29.44

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

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 ...

estimated one-minute mean winds at this time to be at . Weakening commenced soon thereafter, and the system fell below cyclone intensity on 10 May after turning to the west. Lili made

landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...

in northern

the following day as a weak tropical low, and dissipated shortly afterwards. Lili's precursor tropical low caused significant

flood A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...

ing in several villages in Indonesia's Maluku province as a result of heavy rainfall. Flooding also occurred in many locations throughout East Timor, causing damage to infrastructure and cutting off roads. Strong winds were experienced along the length of the cyclone's track, as well as on exposed coastal sections of far-northern Australia; namely the

Top End The Top End of Australia's Northern Territory is a geographical region encompassing the northernmost section of the Northern Territory, which aside from the Cape York Peninsula is the northernmost part of the Australian continent. It covers a ra ...

and northern

Kimberley Kimberly or Kimberley may refer to: Places and historical events Australia * Kimberley (Western Australia) ** Roman Catholic Diocese of Kimberley * Kimberley Warm Springs, Tasmania * Kimberley, Tasmania a small town * County of Kimberley, a ...

, and nearby islands. No injuries or fatalities were reported in connection with the cyclone.

Meteorological history

A moderate to strong pulse of the Madden-Julian Oscillation moved eastwards across 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 Oce ...

during early May, generating unseasonal monsoonal activity throughout the

Indonesian archipelago * See also: Names of Indonesia , location = Southeast Asia and Oceania , waterbody = * Indian Ocean * Pacific Ocean , total_islands = ± 17,000–18,000 islands , major_islands = , area_km2 = 8,300,000 , area_footnotes = , rank = , length ...

and far-northern Australia. The presence of the pulse generated favourable conditions for

tropical cyclogenesis Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs. Tropi ...

in the seas to the north of the Australian continent. This was despite May being outside the traditional bounds of the Australian region cyclone season, which officially concludes on 30 April each year. On 4 May, the

(BOM) noted the formation of a weak tropical low approximately to the north-northwest of

Darwin Darwin may refer to: Common meanings * Charles Darwin (1809–1882), English naturalist and writer, best known as the originator of the theory of biological evolution by natural selection * Darwin, Northern Territory, a territorial capital city i ...

, embedded within a low-pressure trough extending from

Borneo Borneo (; id, Kalimantan) is the List of islands by area, third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Isl ...

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torr ...

. Over the next few days, the tropical low moved slowly southwards over the

while its central

gradually deepened. The system was located within a very favourable environment for further development, with

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 ma ...

s of 29–30 ° C (84–86 ° F), an excellent upper-level poleward

outflow Outflow may refer to: * Capital outflow, the capital leaving a particular economy * Bipolar outflow, in astronomy, two continuous flows of gas from the poles of a star * Outflow (hydrology), the discharge of a lake or other reservoir system *Outflo ...

channel and low vertical

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizon ...

. The

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

(JTWC) issued a

tropical cyclone formation alert A Tropical Cyclone Formation Alert (TCFA) is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Fleet Weather Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone formi ...

at 17:30 UTC on 7 May, noting that formative cloud bands had begun to wrap around the consolidating low-level circulation centre. By this time, winds near

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 ...

had developed within deep

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...

in the system's western semicircle. The storm tracked through the southern

at just below tropical cyclone intensity on 8–9 May, and subsequently passed into the northeastern

Timor Sea The Timor Sea ( id, Laut Timor, pt, Mar de Timor, tet, Tasi Mane or ) is a relatively shallow sea bounded to the north by the island of Timor, to the east by the Arafura Sea, and to the south by Australia. The sea contains a number of reefs, ...

. The system intensified into a Category 1 tropical cyclone on the

at 03:00 UTC on 9 May—the tenth

of the

. Located just within

Tropical Cyclone Warning Centre A Regional Specialized Meteorological Centre (RSMC) is responsible for the distribution of information, advisories, and warnings regarding the specific program they have a part of, agreed by consensus at the World Meteorological Organization as ...

Jakarta's area of responsibility, the storm was named Lili by the

(BMKG). Following suit three hours later, the JTWC assessed the system as the equivalent of a

tropical storm 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. Depen ...

. Lili continued slowly southwards towards Australia during 9 May. Despite the otherwise favourable environmental conditions, the development of the storm was hindered by the presence of dry air in the middle and upper layers of the

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 ...

. Following only a small amount of further intensification, Lili reached peak intensity at 18:00 UTC on 9 May, while located halfway between

Timor Timor is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is divided between the sovereign states of East Timor on the eastern part and Indonesia on the western part. The Indonesian part, al ...

and the

Tiwi Islands The Tiwi Islands ( tiw, Ratuati Irara meaning "two islands") are part of the Northern Territory, Australia, to the north of Darwin adjoining the Timor Sea. They comprise Melville Island, Bathurst Island, and nine smaller uninhabited islands, wi ...

. As a mid-range Category 1 tropical cyclone, Lili had ten-minute

of , gusting to , and a minimum

of 997

(29.44

). The JTWC indicated that one-minute mean winds of were present at the storm's centre. Lili began to decay soon afterwards, as dry air continued to infiltrate the cyclone's inner core and the frictional effects of land interaction inhibited the storm's circulation. Wind velocity decreased steadily, and the BMKG indicated that the system had fallen below tropical cyclone intensity at 12:00 UTC on 10 May. Assuming a westwards track under the influence of a strong subtropical

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 ...

anchored over Australia, the system's structure continued to deteriorate. The JTWC issued their final warning on the system at 21:00 UTC, noting that deep convection had become almost entirely absent, leaving the storm's low-level circulation centre exposed. Lili accelerated west-northwestwards across the Timor Sea, before dissipating while making landfall in northern

, at 06:00 UTC on 11 May.

Impacts

Prior to development into a tropical cyclone, Lili's precursor tropical low tracked southwards across the southern Banda Sea, bringing the storm near

's Maluku Islands. Heavy rainfall and strong winds were experienced on the islands for several days, with impacts peaking at around 12:00 UTC on 8 May. The prolonged rainfall caused significant flooding in numerous places across the region, with the most severe effects occurring in the

Southeast Maluku Regency Southeast Maluku Regency ( id, Kabupaten Maluku Tenggara) is a regency of Maluku, Indonesia. It is coincident with the Kei Islands, except that the city of Tual, although within the Kei Islands geographically and the seat of the Regency's adminis ...

. In particular, the villages of Laitutun on

Leti Island Leti is an Indonesian island, the westernmost of the Leti Islands, and one of the 92 officially listed outlying islands of Indonesia. Leti is located in southwest Maluku province. The main town is Sewaru. The Leti language, a member of Au ...

; Tounwawan in Moa Lakor; and Luang Timur in Mdona Hiera, experienced major inundation to an average depth of . The flooding and strong winds resulted in widespread damage in the villages. Many houses and numerous public facilities sustained damage, causing many residents to be displaced. Lili's strong winds also generated dangerous sea conditions, reportedly causing a ship to sink. Despite not making landfall at tropical cyclone strength, Ex-Tropical Cyclone Lili caused significant impacts in East Timor. Protracted periods of heavy rainfall, with widespread 24-hour totals of , led to river level rise and subsequent flooding. Many roads, bridges and other pieces of infrastructure were damaged by flooding, especially in the eastern half of the country. Other roads and bridges were also cut off or threatened by floodwaters. The primary road link from

Lospalos Lospalos — sometimes erroneously written as ''Los Palos'', assuming a nonexistent Spanish etymology — is a city in East Timor, to the east of Dili, the national capital. Lospalos has a population of 17,186 (2006) and is the capital of L ...

to the national capital

Dili Dili ( Portuguese/ Tetum: ''Díli'') is the capital, largest city of East Timor and the second largest city in Timor islands after Kupang (Indonesia). It lies on the northern coast of the island of Timor, in a small area of flat land hemmed ...

was covered by mud and water, severely impeding the passage of traffic. Damage was sustained in the

Baucau Baucau ( pt, Baucau, tet, Baukau) is the second-largest city in East Timor, after Dili, the capital, which lies to its west. Baucau has about 16,000 inhabitants, and is the capital of Baucau municipality, located in the eastern part of t ...

municipality from riverine flooding. A truck was also submerged in a swollen stream in the south of the country. Damaging winds were experienced on the eastern tip of East Timor, with gusts of approximately . Mild impacts were also experienced across large areas of eastern Indonesia and sections of exposed coastline in the

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an Australian territory in the central and central northern regions of Australia. The Northern Territory shares its borders with Western Au ...

, northern

, and nearby islands. Strong winds and enhanced rainfall occurred throughout the region, as well as large waves and strong tides. McCluer Island, situated off the northern coast of the

; and

Troughton Island Troughton Island is an island located off the Kimberley coast of Western Australia, about north-west of Kalumburu and north-west of the Mungalalu Truscott Airbase. Troughton Island is used as a helicopter base for the Timor Sea oil rigs app ...

, located off

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to ...

's far-northern coast, both experienced sustained winds exceeding , with gusts reaching . Strong winds and moderate rainfall were also observed in the Indonesian provinces of

West Nusa Tenggara West Nusa Tenggara ( id, Nusa Tenggara Barat – NTB) is a province of Indonesia. It comprises the western portion of the Lesser Sunda Islands, with the exception of Bali which is its own province. Mataram, on Lombok, is the capital and largest ...

and

East Nusa Tenggara East Nusa Tenggara ( id, Nusa Tenggara Timur – NTT; pt, Sonda Oriental) is the southernmost province of Indonesia. It comprises the eastern portion of the Lesser Sunda Islands, facing the Indian Ocean in the south and the Flores Sea in the nor ...

, and in parts of Sulawesi. At peak intensity, the BMKG reported that Lili's winds were generating waves of up to in height in parts of the Timor and Arafura Seas. Waves of up to in height were also generated in the ocean and waterways surrounding several islands further to the west.

References

External links

Australian Bureau of MeteorologyIndonesian 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 ** Indonesia ...

)
Joint Typhoon Warning Center
Official severe weather report on Tropical Cyclone Lili
-> {{DEFAULTSORT:Lili (2019) 2018–19 Australian region cyclone season Tropical cyclones in Indonesia Tropical cyclones in East Timor Tropical cyclones in the Northern Territory Category 1 Australian region cyclones Off-season Australian region tropical cyclones