The miraculous journey of IOD (Indian Ocean Dipole) has finally come to an end, with the prominent oceanic parameter becoming neutral. The latest IOD value has been recorded at 0.3 degree Celsius. But this journey of IOD, which is invariably linked with good Monsoon rains, has etched some records in the history of Indian Monsoon.
2019 has been exceptional year for the country in terms of rains. First it was excess Monsoon rains since 1974, followed by nine cyclones in the post Monsoon season that is highest ever in the Indian history.
Beginning of the season was not promising but picture changed entirely as we progressed further. The credit goes to IOD, which has been a game changer for Monsoon 2019 that was predicted to be below normal initially. It even defied the deadly phenomena of El Niño, whose mere presence holds the capacity to corrupt the entire Monsoon season.
For the fact, El Niño was quite strong during the initial months of 2019, due to which we saw poor pre-Monsoon rains, followed by delayed onset of Monsoon 2019 in June and drought like conditions in the onset month to the tune of 77%.
IOD was not only positive but was strongest ever in the history. This had driven the Monsoon crazy that finished with whopping figure of 110% i.e. excess.
Right from April, IOD was neutral on the positive side. However, May onward it gained strength and became strongly positive during the Monsoon months. According to statistics, it has been the longest spell which went on till December with IOD values maintaining above the threshold value that stands at 0.4 degree Celsius. Besides this, IOD value had reached maximum of 2.2 degree Celsius, which is also highest ever.
According to weathermen, the decline in IOD values this season has been very-very gradual, or we should say a delayed one.
Usually, post the departure of the Southwest Monsoon, the Intertropical Convergence Zone (ITCZ), which is primarily responsible for churning out Monsoon systems starts moving southwards to Southern Hemisphere. Simultaneously, IOD also does not remain of much significance.
However, any of such thing did not happen this year. Presence of IOD along with active ITCZ kept the weather conditions conducive for formation of back to back weather systems during the post Monsoon season. Not only sea conditions were favourable but ripe enough that maximum of the system wet ahead and attained the status of cyclonic storms.
Nine cyclones were recorded in the Indian seas during the year, with six forming in Arabian Sea and three in Bay of Bengal. Usually Bay of Bengal record a greater number of cyclones in comparison to Arabian Sea.
IOD AND SOUTHWEST MONSOON 2020
Coming back to present status of IOD, the weather models are projecting that IOD values are going to remain neutral at least till June.
Now, as we progress to another season of the Monsoon, again all eyes would be on development of IOD in the coming year. However, weathermen are of the view that back to back positive as well strong IOD is not witnessed in the history.
Nonetheless, nothing is written in the rulebook. So, who knows we could see another miracle in the upcoming Southwest Monsoon 2020.
Image Credit: NDTV
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