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Posts Tagged ‘Indian Ocean

Winds of monsoon India

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This panel of four images shows: top left, winds at around sea level; top right, winds at about 1,460 metres altitude (around 4,780 feet); lower left, winds at 3,010 metres (9,880 feet); lower right, winds at 5,570 metres (18,280 feet).

These are the wind patterns that are bringing the monsoon to us from just above the equator, as they travel east-north-eastwards towards the Indian peninsula, and earlier north-north-westwards as they travelled from near Madagascar and the Mascarene Islands, which lie about 21 degrees south of the equator.

RG_India_monsoon_winds_20150613_bIn the top two images, the south-west (from our point of view) winds sweeping across the Arabian Sea are the dominant feature, with the winds at the higher of the two altitudes (right, at 850 millibars, or mb, which is around 1,460 metres) rushing in at just the direction and velocity they ought to. Winds at near-sea level are less powerful, and in both the two top images winds are also seen travelling due north up the Bay of Bengal.

In the lower two images, the vortex of Cyclone Ashobaa is clearly seen, with wind trails running due east across the Arabian Sea, then across peninsular India and out over the Bay of Bengal towards Burma. More markdly with the winds in the lower left image, which are at 700 mb or 3,010 metres, they scarcely touch central and north-western India and the Gangetic belt (whereas the winds at lower altitudes, as seen in the upper two images, do).

Finally, in the lower right image are the winds at 500 mb, or 5,570 metres. Here we see them streaming powerfully down from the Hindu Kush-western Himalaya, across north India and thence right across the Gangetic belt, through Assam and the north-east. These are the major wind patterns we have now in mid-July, and they will change in strength, direction and intent as El Nino changes and also as the Northern hemisphere summer continues over the Eurasian land mass.

These wonderful images are taken from the ‘earth’ weather observation visualisation which skillfully employs the forecasting by supercomputers of current weather data from the Global Forecast System (GFS) and the NOAA/NCEP climate and weather modelling programmes.


Written by makanaka

June 13, 2015 at 21:54

How El Niño plans to hijack monsoon 2015

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Whether the monsoon starts off on time, whether the June, July, August and September rainfall averages are met, and whether the seasonal pattern of the monsoon is maintained are expectations that must now be set aside.

According to the Climate Prediction Center’s ENSO probability forecast, there is a 90% chance that El Niño conditions will prevail through June to August of the northern hemisphere and a more than 80% percent chance El Niño will last throughout all of 2015.

What this means, especially when record warm global atmospheric temperatures (because we in South Asia and our neighbours in East Asia have continued burned coal as if the resulting CO2 and soot simply doesn’t exist) are being set, is the remaining months of 2015 – the monsoon period included – will bring strange, dangerous and extreme weather. We have already seen that over the last week, with the death toll from the heat wave having crossed 550.

The Ministry of Earth Sciences El Niño/La Nina, Indian Ocean Dipole Update (10 May 2015)

The Ministry of Earth Sciences El Niño/La Nina, Indian Ocean Dipole Update (10 May 2015)

For the first time since 1998 – ­the year of the strongest El Niño on record, which played havoc with the world’s weather patterns and was blamed for 23,000 deaths worldwide – ­ocean temperatures in all five El Niño zones have risen above 1 degree Celsius warmer than normal at the same time. That is read by climatologists and ocean scientists as presaging an El Niño that is moderately strong to strong. The forecast models updated in May are now unanimous that El Niño is going to keep strengthening through the rest of 2015. (See also the official forecast from the USA’s government climate science agency.)

El Niño’s home is in the tropical eastern Pacific, but we in India need to watch the waters to our south very closely. New research published in the journal Nature Geoscience has examined records going back to 1950 and noticed that Indian Ocean absorbed heat at a low level until 2003. Thereafter, the excess oceanic heat in the Pacific Ocean found its way through the Indonesian archipelago and into the Indian Ocean. This is the gigantic reservoir of watery heat that is going to dictate terms to our summer monsoon, or what our school textbooks call the south-west monsoon.

It is a worry for the entire South Asian region – India, Pakistan, Sri Lanka, Bangladesh, Nepal, the Maldives, Burma, Afghanistan and Bhutan. That is why when the Forum on Regional Climate Monitoring-Assessment-Prediction for Asia (FOCRA) issued its seasonal outlook for June to August 2015 it predicted weaker than normal Indian summer and East Asian monsoons. Precipitation over land is influenced by external factors such as the El Niño Southern Oscillation (the ENSO), the ‘Indian Ocean Dipole’, the ‘Arctic Oscillation’, and so on.

There may be a “timely onset” of the monsoon, as the venerable IMD is used to saying, but that doesn’t mean our troubles are over. Far from it.

India lowers its 2011 monsoon forecast

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India’s meteorological department has issued its second long range forecast for the 2011 monsoon and has lowered its estimate. Rainfall will be 95% of the 50-year average in the June-September season, which are the monsoon months. In April, the Indian Meteorological Department predicted a monsoon that would be 98% of the long-term average. Normal precipitation is considered to be 96%-104% percent of the long-term average.

India’s agriculture-dependent population has been hoping for adequate rainfall to harvest good quantities of foodgrain and lentils for a second year and bring down inflation, which has led the Reserve Bank of India – the central bank – to raise rates for a 10th time in 15 months. Agriculture accounts for 14% of the economy and a reduced harvest can further lower rural incomes and send food inflation higher than it already is. Inflation in India is the highest among Asia’s major economies.

Bloomberg reported that the wholesale price index in India accelerated 9.06% in May after having increased 8.66% a month earlier, according to official data released on June 14. An index measuring wholesale prices of farm products including milk and lentils rose 8.96% in the week ended June 4 from a year earlier, according to the commerce ministry. India imported record quantities of sugar, lentils and oilseeds in 2009 following the weakest monsoon that year since 1972.

The IMD’s ‘long period’ is 1951-2000 and the department considers probabilities for the country (all-India) and four major regions: north-west India, central India, north-east India and south peninsula. “Over the four broad geographical regions of the country, rainfall for the 2011 Southwest Monsoon Season is likely to be 97% of its LPA over North-West India, 95% of its LPA over North-East India, 95% of its LPA over Central India and 94% of its LPA over South Peninsula, all with a model error of ± 8 %.”

The IMD also employs a six-parameter statistical forecasting system to prepare probability forecasts for five pre-defined rainfall categories. These are deficient (less than 90% of LPA), below normal (90-96% of LPA), normal (96-104% of LPA), above normal (104-110% of LPA) and excess (above 110% of LPA). The forecasted probabilities for the 2011 southwest monsoon season based on this system in percentage for the above 5 categories are 19%, 37%, 37%, 6% and 1%

The department’s ‘Summary of the Update Forecasts for 2011 Southwest Monsoon Rainfall’ has said:

(1) Rainfall over the country as a whole for the 2011 southwest monsoon season (June to September) is most likely to be below normal (90-96% of LPA). Quantitatively, monsoon season rainfall for the country as a whole is likely to be 95% of the long period average with a model error of ±4%. The Long period average rainfall over the country as a whole for the period 1951-2000 is 89 cm.

(2) Rainfall over the country as a whole in the month of July 2011 is likely to be 93% of its LPA and that in the month of August is likely to be 94% of LPA both with a model error of ± 9 %.

(3) Over the four broad geographical regions of the country, rainfall for the 2011 Southwest Monsoon Season is likely to be 97% of its LPA over North-West India, 95% of its LPA over North-East India, 95% of its LPA over Central India and 94% of its LPA over South Peninsula, all with a model error of ± 8 %.

According to Reuters, government officials played down concerns that lower rainfall could fan inflation and dampen growth. “There is no need to press the panic button, as June rains are still above normal,” said Shailesh Nayak, the top civil servant in the ministry of earth sciences which controls the country’s weather office.

While rains could be slightly lower than normal in July, India’s chief forecaster said distribution was key. “There are chances the monsoon will pick up after July 15 once it covers the entire country,” said D. Sivananda Pai, director at the state-run National Climate Center. “Don’t go by the numbers, it is the distribution (of the rains) which we are still hoping to be good.” The weather office predicted 27 centimetres of rain in July compared with long-term average rainfall of 29 centimetres, and rains at 24 centimetres in August, when seeds start maturing, compared with long-term averages of 26 centimetres.

Weather office chief Ajit Tyagi remained optimistic. “Ninety five percent is a good forecast,” Tyagi said. “Had it been 90% of the long-term average then it would have been a cause for concern,” he said, adding that in the past slightly below normal monsoon rains had also seen adequate farm output because they were well distributed in the major crop growing regions.

Explaining climatic conditions over the equatorial Pacific and Indian Oceans, the department’s second long range said moderate to strong La Nina conditions that prevailed in the equatorial Pacific during mid-August 2010 to early February 2011 weakened during subsequent months and dissipated to neutral conditions around mid-May 2011. The latest forecasts from a majority of the dynamical and statistical models indicate strong probability for the present ENSO-neutral conditions to continue during the current monsoon season and the remaining part of 2011.

It is important to note that in addition to El Niño and La Niña events, other factors such as the Indian Ocean Sea surface temperatures (SSTs) have also significant influence on India monsoon. However, the latest forecasts do not suggest development of either a positive or a negative Indian Ocean Dipole event during the 2011 monsoon season. In the absence of strong monsoon forcing from both Pacific and Indian Oceans, intraseasonal variation may become more crucial during this southwest monsoon season and lead to increased uncertainty in the monsoon forecasts.