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First look: India may have a good monsoon in 2020

Vinson Kurian January 23 | Updated on January 23, 2020 Published on January 23, 2020

Aerial image over the sea at sunset istock/nattrass

Early outlook from global models says positive IOD will help; summer should be cooler for the northern half of the country and warmer in the South

The earliest available (January-based) outlook for global weather indicates the possibility of a recurrence of a weak to moderate Indian Ocean Dipole (IOD) phase and a reasonably good monsoon for India this year. This follows one of the strongest ever episodes of a positive IOD on show in the year just past (2019-20) and an excessively wet Indian South-West (June-September) monsoon in 2019. (These are January-based outlooks from international models, and are due for updates every month. BusinessLine will carry these updates in February, March, April, May and into the monsoon).

Moderate positive IOD in works?

The Application Laboratory of Japanese national forecaster Jamstec noted in its January-based outlook that the strong positive IOD of 2019-20 has almost disappeared. However, its model predicts the evolution of another moderately positive IOD from the summer, while cautioning that there is huge uncertainty in the prediction at present due to the large spread in the prediction of the IOD index values.

The Ningaloo Nino, a marine heat wave off the West Coast of bushfire-hit Australia, has quickly emerged in December 2019. This wave is a warm surge within an ocean current that flows South from Indonesia. The model predicts that the Ningaloo Nino, which has bleached coral reefs and caused a massive fish die-off, will persist until late February. On a seasonal scale, Jamstec’s Application Laboratory predicts that most parts of the globe will experience warmer-than-normal conditions into March. The summer that follows may experience hotter-than-normal conditions.

Recurrence not very common, says Skymet Weather

Closer home, private forecaster Skymet Weather said that recurrence of positive/negative IOD episodes is not very common, though there have been exceptions (1982 and 1983, positive IOD). But the influence of a concurrent El Nino event in the Pacific made the difference; it has the power to neutralise IOD. Given this, it is not inconceivable that there will be another positive IOD evolving this year. The picture will become clearer around April.

Statistically, the IOD has a ratio of 1:1:4 with respect to positive, negative and neutral events, respectively. Since 1960, there have been 13 incidents of a positive IOD, 12 of a negative IOD and 35 of a neutral IOD. These events do not form during the southern summer (as it does currently in Australia) and autumn because the monsoon trough (or the Inter Tropical Convergence Zone, ITCZ) lies in the South over the tropical Indian Ocean.

In the Equatorial Pacific, the sea surface temperatures are near to above average in ascending orders in value from the East coast and westward to the Central Pacific, Skymet Weather noted. There is a probability of around 60 per cent of neutral conditions (neither El Nino nor La Nina) prevailing through March 2020 and 50 per cent chance that they will last into the ensuing Summer season.

El Nino being not around itself is great news for the Indian monsoon, the Skymet Weather analysis said. Last year (2019), a declining El Nino had not only delayed the onset of the monsoon but also impacted rainfall. June ended with a rain deficit of 33 per cent, equivalent to a drought-like situation, though reversed in style later by a strong positive IOD.

Preliminary outlook for weather and climate into the spring and summer from global models is as follows:

1. Application Laboratory, Jamstec (probability report on seasonal predictions):

Temperature from March-April-May: Most of India cooler than normal except western parts of Peninsular India and the West Coast, which are likely to be warmer.

June-July-August: Most of India warmer than normal except the monsoon-hit South. Most parts cooler than normal except Peninsular West, South and West Coast, West Maharashtra, Coastal Maharashtra, Coastal Karnataka, and Kerala.

Rainfall: Normal rainfall for both March-April-May and June-July-August

2. APEC Climate Centre, Busan, South Korea:

Temperature February-March-April: Cooler over most of northern India except East Jammu & Kashmir. Slightly above normal for most parts of the Peninsular South. Hotter over Karnataka, South Kerala and Coastal Tamil Nadu.

May-June-July: Hottest over West Rajasthan, Gujarat, Saurashtra, Kutch, West Coast and adjoining interior including Konkan (Mumbai), Goa, Karnataka, Kerala,

Rainfall in February: Above normal rain for Central and adjoining East India, northern parts of the peninsula. Below normal for Rayalaseema, Gujarat, Kerala, Tamil Nadu, South Interior Karnataka.

March: Almost the same scenario as in February but more parts of Central India and adjoining North-West India to see above-normal rain. Below-normal for Kerala, Karnataka, entire Karnataka (North Interior and South Interior) and Tamil Nadu.

April: Above normal for Central, North and North-West India. Below-normal for Gujarat, most parts of Peninsular India, East Coast, Kerala, Karnataka, Tamil Nadu, Andhra Pradesh, Telangana. Deficient over Vidarbha, Chhattisgarh and Odisha.

May: Above-normal for Kerala, Karnataka and most of Tamil Nadu. Very wet over South Kerala, Lakshadweep, Sri Lanka, Maldives, Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Nepal.

June: Very wet over Kerala, South Tamil Nadu. Slightly less wet over rest of Tamil Nadu, Andhra Pradesh, Karnataka. Very strong monsoon seen, Mumbai-Gujarat coast in particular. Probability of depression/cyclone.

July: Surplus monsoon all over country. Active Arabian Sea (focus over land in Gujarat) and Bay of Bengal (South Andhra Pradesh coast) seen. Deficient rain over West India, East and North-East India; particularly bad over North-East India.

March-April-May: Below normal for West Coast and adjoining West Madhya Pradesh, West Maharashtra, Central Karnataka, Kerala. Normal over the rest of the country and slightly above normal over Jammu & Kashmir, Himachal Pradesh, Uttarakhand.

June-July-August: Normal over South Peninsular India—Kerala, Karnataka, Andhra Pradesh, Telangana. Below normal over rest of the country except Chhattisgarh, Odisha, East Rajasthan and adjoining Delhi.

Deep colours shine in the sky as the sun sets over Lombok istock/CreativeMoments

 

3. The UK Met Office

Temperature: February-March-April: 40 to 60 per cent probability of cooler-than-normal conditions for the northern and eastern one-third of the country. Sixty to eighty per cent probability for slightly above-normal for the central one-third. 80-100 per cent probability for above-normal conditions for the southern one-third.

March-April-May: A patch of dryness from Bay of Bengal extending South-West to Sri Lanka and extending a limb into South Peninsular India, especially Kerala and adjoining South Tamil Nadu.

Rainfall in February-March-April: Above normal rain for almost the entire northern half of the country and adjoining East India, though not North-East India. No signal for Central India (likely normal).

March-April-May: No signal for most parts of the country (likely normal) except a narrow corridor of wetness along the hills of North-West India. Jammu & Kashmir, Himachal Pradesh, Uttarakhand and West Uttar Pradesh.

April-May-June: Wet over South Peninsula with onset of monsoon. Especially wet over Tamil Nadu, Karnataka, Andhra Pradesh, Telangana. Monsoon flows good off the Equator and around Horn of Africa. A blob of above normal rainfall off off the Oman-Yemen coast could suggest a weather system (depression/cyclone) from the monsoon system.

May-June-July: Very strong monsoon along the West Coast. Good rain for Kerala, Tamil Nadu, Karnataka, Andhra Pradesh, Telangana. Monsoon flows good South of the Equator and around Horn of Africa.

4. International Research Institute for Climate and Society, Columbia University

Temperature in February-March-April: No signal (therefore likely normal conditions) for most of the country except in West Rajasthan, Punjab, Himachal Pradesh and Jammu & Kashmir and parts of South Coastal Tamil Nadu where it could be above normal.

March-April-May and April-May-June: Almost similar conditions as in February-March-April. Parts of Goa, North Interior Karnataka could be exception (warmer) during April-May-June.

May-June-July: No signal for most parts of the country but cooler over West Madhya Pradesh and adjoining western parts of Maharashtra, and Goa.

Rainfall in February-March-April: Below normal for South Kerala and adjoining South Tamil Nadu, Chhattisgarh, Vidarbha. Above normal for Delhi, Chandigarh, Haryana, West Uttar Pradesh, East Uttar Pradesh, Bihar, and Bengal.

March-April-May: Normal for most parts of the country. Small areas of deficiency in West Madhya Pradesh, South Uttar Pradesh, and Odisha.

April-May-June: Above normal for South Kerala, South Tamil Nadu. Deficiency over North Tamil Nadu. Above normal for East Madhya Pradesh, parts of adjoining Bihar.

May-June-July: Normal for North Karnataka, adjoining Rayalaseema, Gujarat, Rajasthan, Delhi, Chandigarh, Punjab, Himachal Pradesh, Jammu & Kashmir. No marked deficiency anywhere.

Southeast Asia on a 3D model of Earth.

 

5. European Centre for Medium-Range Weather Forecasts

Temperature: Cooler than normal for most parts of the northern half of the country through February-March-April (coolest), March-April-May, April-May-June and May-June-July. Hot over South India and along West Coast, Rajasthan and Gujarat in April-May-June and May-June-July.

Rainfall in February-March-April: No marked deficiency anywhere. Above normal along the hills of North-West India, and adjoining plains. Heavy over Himachal Pradesh, Uttarakhand, West Uttar Pradesh, East Uttar Pradesh, Bihar. Below normal for Sri Lanka.

March-April-May: Normal for most parts. Slightly above normal over North-West, Delhi, Chandigarh, Haryana and adjoining East Rajasthan.

April-May-June: Mostly normal all over. Except North-East India, adjoining Bangladesh, Myanmar, and Indo-China.

May-June-July: Strong monsoon conditions for most of Peninsular India, including Konkan and Goa. Strong flows off Equator, Arabian Sea and Bay of Bengal.

 

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Published on January 23, 2020
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