2017 North Indian Ocean cyclone season

The 2017 North Indian Ocean cyclone season is a current event in the annual cycle of tropical cyclone formation. The North Indian Ocean cyclone season has no official bounds, but cyclones tend to form between April and December, with the two peaks in May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean.

The scope of this article is limited to the Indian Ocean in the Northern Hemisphere, east of the Horn of Africa and west of the Malay Peninsula. There are two main seas in the North Indian Ocean — the Arabian Sea to the west of the Indian subcontinent, abbreviated ARB by the India Meteorological Department (IMD); and the Bay of Bengal to the east, abbreviated BOB by the IMD. The official Regional Specialized Meteorological Centre in this basin is the IMD, while the Joint Typhoon Warning Center (JTWC) releases unofficial advisories. On average, three to four cyclonic storms form in this basin every season.^[1][2]

Season summary

The season officially had a early start compared with the last two seasons with the formation of Cyclonic Storm Maarutha over the Bay of Bengal in mid-April.The strongest storm of the season so far was Severe Cyclonic Storm Mora, which formed in late May over the Bay of Bengal. The system made landfall in Bangladesh with three-minute sustained winds of 110 km/h (70 mph), and one-minute sustained winds of 120 km/h (75 mph). At this strength, its peak intensity, it was equivalent to a marginal Category 1 hurricane on the Saffir-Simpson hurricane wind scale. The cyclone produced severe flooding across Sri Lanka, India , Myanmar and Bangladesh and caused 15 deaths directly and 203 deaths indirectly. The floods persisted in Bangladesh since a Deep Depression over Bay of Bengal made landfall and killed 156 people in Bangladesh. A depression formed in northwestern Bay of Bengal and produced torrential rainfall. It was followed by a depression over Jharkhand which killed 16 people in West Bengal.

Systems

Cyclonic Storm Maarutha

Cyclonic storm (IMD)
Tropical storm (SSHWS)
Duration	April 15 – April 17
Peak intensity	75 km/h (45 mph) (3-min)  996 hPa (mbar)

On April 13, an area of low pressure formed in the South Bay of Bengal, under the influence of a persistent area of convection, in a span of six hours.^[3] Under favorable conditions, rapid deepening took place, and the system was classified as a depression on April 15.^[4] Later on the same day, it further intensified into a Deep Depression, and then into Cyclonic Storm Maarutha.The system moved very fast under the influence of mid-latitude trough in westerlies lying over India in the middle and upper tropospheric levels.^[5] However, strong vertical wind shear and unfavourable MJO inhibited rapid intensification or further intensification of the system. Moving northeastwards, it reached its peak intensity in the early hours of 16th. The system maintained its peak intensity till landfall near Sandoway (Thandwe) in Myanmar in the midnight. After landfall, the system weakened into a Deep Depression in early hours of 17th, into a Depression in the morning and well marked low pressure area over central Myanmar and neighbourhood in the forenoon of 17th.^[6]

Maarutha had already triggered heavy rainfall as a depression in Sri Lanka, as well as the Andaman and Nicobar Islands (India).Due to a heavy swell in the sea around the Andaman Islands, all ferries to Havelock Island from Port Blair were suspended on leaving nearly 1,500 tourists stranded. ^[7]In Kyaukpyu, Maarutha destroyed more than 81 households and total damages amounted to Ks31.8 million (US$23,400) as of April 18.^[8] Four people were reported to be killed in the Irrawady division of Myanmar.^[9][10] Maarutha developed as a depression in the first fortnight of April. Climatologically, the formation of tropical cyclones in the Bay of Bengal at this time of the year is rare. Only twelve cyclones have developed over the Bay of Bengal during 1891-2016.

Severe Cyclonic Storm Mora

Severe cyclonic storm (IMD)
Category 1 tropical cyclone (SSHWS)
Duration	May 28 – May 31
Peak intensity	110 km/h (70 mph) (3-min)  978 hPa (mbar)

Under the influence of a persistent area of convection, a low-pressure area formed over the southeast Bay of Bengal on May 26. It rapidly strengthened on May 28 with the IMD classifying it as a Depression and subsequently into a Deep Depression on the same day, designating it BOB 02. In the early hours of May 29, the IMD reported the storm to have reached Cyclonic storm intensity, naming it Mora. The storm followed a north-northeasterly track parallel to Myanmar coast.The system moved fast under the influence of mid-latitude trough in westerlies lying over India in the middle and upper tropospheric levels and the anti-cyclonic cyclonic circulation lying to the northeast of the system. Shortly before landfall, the storm reached its peak intensity as a severe cyclonic storm with winds of 110 km/h and a minimum central pressure of 978 hPa (mbar).The JTWC analysed it having reached Category 1 hurricane strength with winds of 120 km/h on the same day. At peak intensity, the storm made landfall on the southern coast of Bangladesh near Chittagong at IST 6:00 am. After landfall, the storm steadily weakened due to land interaction and dissipated into a well-marked low-pressure area over Nagaland on May 31.^[11]

A total of 31 people have been killed—9 in Bangladesh and 1 in Myanmar and 19 in Manipur^[12][13][14] Damage throughout Bangladesh reached 44 to 45 crore in taka and in Myanmar it reached to USD 1.5 million. In India it reached to 131 crore (USD 20 million).^[15][16][17] Two people were reported to be killed in Malda district of West Bengal.^[18]

Also, although not directly related to the storm, the precursor low of Mora strengthened the arrival of the monsoon, causing heavy flooding in Sri Lanka and the Andaman Islands that killed more than 200.

Deep Depression BOB 03

Deep depression (IMD)
Duration	June 11 – June 13
Peak intensity	55 km/h (35 mph) (3-min)  988 hPa (mbar)

A depression originated from a monsoonal low pressure area on June 11 in north west bay of bengal and was assigned the designation BOB 03 by the India Meteorological Department. The system strengthened into a deep depression before making landfall in Bangladesh at about 5:00 am local time on 12 June (23:00 UTC, 11 June).^[19] At peak intensity, the system had three-minute sustained winds of 55 km/h (35 mph), and a minimum central pressure of 988 hPa (29.18 inHg). At least 156 people have been confirmed dead following landslides caused in the Rangamati, Bandarban and Chittagong districts of Bangladesh along with 14 others in Northeast India caused by torrential rainfall.^[20][21] The IMD published its final bulletin on the system following its weakening below tropical depression intensity into a "well-marked low pressure area," at 02:30 UTC on 13 June.^[22] The system helped in the advancement of monsoon over the regions of West Bengal and Odisha. Damages included loss of Tk 1800 crore (USD $223 million).^[23]

Depression BOB 04

Depression (IMD)
Duration	July 18 – July 19
Peak intensity	45 km/h (30 mph) (3-min)  992 hPa (mbar)

A low pressure area consolidated into a depression over the northwestern and adjoining west-central Bay of Bengal off Odisha coast on July 17. The IMD began issuing advisories on a depression that it was very likely to cross the coast by night.The depression moved in a generally northwestwards direction without intensifying, and made landfall on India's Odisha coast, south of Puri, at about 15:00 UTC (20:30 IST) on July 18. Heavy rainfall and sustained winds of 45 km/h (30 mph) affected the region,^[24] causing at least a dozen villages to be submerged in floodwater and five bridges to be washed away.^[25] As many as 6,000 people were evacuated in Nabarangpur, and an estimated 65,000 people were directly affected by the dangerous weather.^[25] As of July 31, at least seven people have been killed as a result of the storm.^[25] Total losses were estimated at Rs 219 crore.^[26]

Land Depression 01

Depression (IMD)
Duration	July 26 – July 27
Peak intensity	45 km/h (30 mph) (3-min)  992 hPa (mbar)

A well-marked low-pressure area over Jharkhand and adjoining the Gangetic West Bengal intensified into a depression on July 26. It moved in a west-northwest direction until degenerated to a well marked low pressure area over east Madhya Pradesh during the next day.

The storm in its precursor low caused dangerous floods in West Bengal. At least 50 people died while nearly 20 lakh were affected in over 160 villages, which were inundated due to heavy rains. 2,301 people were evacuated from their houses and 2,02,957 hectare of agricultural land was submerged. Around 7,868 houses were entirely destroyed while 44,361 were partially damaged in West Bengal.^{[27] [28]} The state lost around Rs.553 crores(USD $86.6 million) due to the storm.^[29]Eleven people were reported to be killed in Jharkhand due to heavy rains.^[30]

Storm names

Within this basin, a tropical cyclone is assigned a name when it is judged to have reached cyclonic storm intensity with winds of 65 km/h (40 mph). The names were selected by members of the ESCAP/WMO panel on Tropical Cyclones between 2000 and May 2004, before the Regional Specialized Meteorological Center in New Delhi started to assign names in September 2004. There is no retirement of tropical cyclone names in this basin as the list of names is only scheduled to be used once before a new list of names is drawn up. Should a named tropical cyclone move into the basin from the Western Pacific, then it will retain its original name. The next six available names from the list of North Indian Ocean storm names are below.

Season effects

This is a table of all storms in the 2017 North Indian Ocean cyclone season. It mentions all of the season's storms and their names, duration, peak intensities (according to the IMD storm scale), damage, and death totals. Damage and death totals include the damage and deaths caused when that storm was a precursor wave or extratropical low, and all of the damage figures are in 2017 USD.

See also

• 2017 Atlantic hurricane season
• 2017 Pacific hurricane season
• 2017 Pacific typhoon season
• South-West Indian Ocean cyclone seasons: 2016–17, 2017–18
• Australian region cyclone seasons: 2016–17, 2017–18
• South Pacific cyclone seasons: 2016–17, 2017–18

References

External links

Wikimedia Commons has media related to 2017 North Indian Ocean cyclone season.

• India Meteorological Department
• Joint Typhoon Warning Center

Tropical cyclones of the 2017 North Indian Ocean cyclone season
	CS Maarutha SCS Mora DD BOB 03 D BOB 04 D LAND 01
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