“This is the fifth article related to the monsoon season of 2013 and it will be followed by many more articles”
‘Indian Ocean is giving threats to the Monsoon!’
El Niño/La Niña–Southern Oscillation of Pacific Ocean is not the only thing that is an obstacle in the way of monsoon season but there is a similar phenomenon in the Indian ocean that has an impact on the monsoon seas though it affects less number of countries than the ENSO conidtions. What is it? It is the Indian Ocean Dipole (IOD), this year it is the only thing that is giving threats to the upcoming monsoon season especially to Pakistan!
Indian Ocean Dipole and monsoon
IOD is an irregular phenomenon in which the western equatorial of the Indian Ocean becomes warmer while the eastern equatorial cooler or vice-versa.It affects the Sub continent, Australia, Indonesia and many other surrounding countries. There are two phases of Indian Ocean Dipole; 1. Positive IOD 2. Negative IOD
- Positive Indian Ocean Dipole (IOD) causes sea temperatures to rise in the western Indian Ocean with heavy precipitation in Sub-continent while it makes the sea temperatures cooler in the eastern Indian Ocean with drought or very little to no precipitation in Australia and Indonesia.
- Negative Indian Ocean Dipole (IOD) causes cooler sea temperatures in western Indian Ocean with less rainfall in the Sub-continent while eastern Indian Ocean becomes warmer with heavy precipitation in Indonesia and some parts of Australia.
Early Monsoon – Danger during last months?
‘American and Australian saying bad monsoon ahead!’
According to the American and Australian experts, a negative Indian ocean Dipole is very likely this year that will remain towards the end of Monsoon season. According to their models which show that a sharp transition would take place during last week of May as shown in the above chart which will result in the formation of a negative Indian ocean Dipole hence the onset of monsoon would be delayed in western India and all over Pakistan, these areas will continue to witness below normal rains till the end of monsoon.
The Australian Meteorology also points towards cooler temperature in the Pacific Ocean that might led to a weak La-Nina later in the year. Four out of five Australian models hints towards a negative Indian ocean dipole during the upcoming monsoon season.
‘Japanese worry too – Little cautious at the moment!’
The Japanese on the other hand were the first to point out that negative Indian ocean Dipole would develop this year though they are little cautious this year as their model failed last year to predict the sudden development of positive Indian ocean dipole during last days of monsoon season that in return caused heavy flooding in parts of Sub-continent.
According to their model, monsoon could create some problems in some places of north-eastern, central and adjoining north-western parts of India though at the same time, the same model that is forecasting for Negative Indian Ocean dipole is forecasting a weak La-Nina later in the season.
‘South Korea believes a good monsoon ahead’
South Korea-based Asia-Pacific Climate Centre have ruled out that there will be below normal rains this year in the sub-continent. Their model expects overall normal to above normal monsoon rainfall during June and July while slight decrease in rain-coverage in the month of August.
‘Indians neglect -IOD’
The forecast of Indian Meteorological Department (IMD) has not mentioned the Negative India Ocean Dipole development, in simple words they have completely neglected the Indian ocean Dipole phenomenon therefore they believe on a normal monsoon season.
Breif Timeline of 2013 Monsoon season
It was feared that the low pressure that formed in the Arabian sea off the coast of Oman, if it intensifies then it would drag the moisture away from the sub-continent thus causing a delay in monsoon’s westward advancement but the monsoon was saved as the low pressure near Oman fizzled though some decrease in thunderstorm activity over western India coast did occur which will improve in few days and a second depression BOB 02 formed in the Bay of Bengal that moved towards north-eastern areas of Indian causing monsoon onset over many parts of India. Following are the important dates on which monsoon arrived over the sub-continent;
- May 17 – Andaman sea and south Bay of Bengal
- June 1 – Kerala, PWP had predicted that it will hit early than IMD’s June 3 forecast.
Two low pressures formed in the Arabian sea both were unimportant for the sub-continent. In the both of Bay of Bengal, two depressions formed, in which one of intensified into a cyclone ‘Mahasen’.
Early Monsoon has been vigorous
So far the sea surface temperatures of the Pacific ocean are neutral though later this year a weak La-Nina can develop during late July/August and during this period the negative India ocean dipole is expected to peak, both of these phenomenons will influence the monsoon season. So far the monsoon has been vigorous over India as 26% above normal rainfall has occurred. From June 9, the monsoon coverage in the sub-continent would increase significantly. Two low pressure from the Bay of Bengal can move towards central India, another circulation can form in the North Arabian sea.
Our View on the upcoming season
Pakistan Weather Portal (PWP)’s monsoon forecast that was issued on May 6 has been revised on June 6, following is the forecast of PWP;
“Monsoon 2013 would set in early this year in India due to the formation of a low pressures in Bay of Bengal, Monsoon will be very active in the month of June as there is a possibility of pre-monsoon in Sindh and Punjab, moderate to heavy downpour can occur in Punjab (including Lahore) and Sindh (including Karachi) during the late midweek and last week of June due to the weak Madden-Julian Oscillation (MJO) wave. Eastern & western winds interaction possible during this period of June and later in the season in upper areas of Pakistan which could lead to heavy rainfall over Khyber Pakhtunkhwa as well. Monsoon onset in Pakistan can take place in the last weeks of June/first week of July especially in the northern areas of the country. Pakistan can experience near to normal rainfall in June till early July on the wider-scale while normal to below normal rainfall after mid-week of July till August as a whole. North-eastern Punjab and Azad Kashmir can witness some frequent heavy downpour in the month of July. Due to the high possibility of the formation of negative Indian ocean Dipole, rain activity could be significantly hampered from mid-week of July and in August, a partial effect of weak La-Nina might be observable later in the monsoon season (which could weaken the effect of -IOD in September). However an event of isolated flash flooding/urban flooding (happens every year) can never be ruled out.”
Monsoon Special articles for 2013
You can read special monsoon article by Pakistan Weather Portal (PWP), here;
- Another Monsoon brewing for the same Sub-continent! – Part I
- Do we really need a monsoon season? – Part II
- Pakistan bakes in Oven: Bricks for Monsoon 2013 placed! – Part III
- Look back at Past: Pre-Monsoon rains are just around the corner? – Part IV
- Monsoon facing the biggest challenge from its own Ocean! – Part V
- Road map for ‘Monsoonistan’ laid: Rains move into Pakistan! – Part VI
TO BE CONTINUED……