Much to everybody’s surprise, El Niño has turned out to be late bloomer this time. The probability percentage has gone for a toss, with sea surface temperatures (SST) soaring high during the last two weeks after dropping below average temperatures at 0.3°C on February 4.
El Niño is famous for not behaving in similar pattern or same place every time it appears. There is no rule book for the same, keeping meteorologists on toes as it affects large parts of world.
Since the beginning of February 2019, positive SST anomalies have strengthened across most of the equatorial Pacific Ocean, particularly last fortnight has seen significant increase. Even the sub surface temperatures up to about 200 meters have also shown rise in heat content. Here’s a look at the recent Niño Index (in °C):
According to weathermen, the reason behind the sudden rise can be attributed to the passage of active MJO (Madden–Julian oscillation), which had resulted in weakening of trade winds. With this, the probability of El Niño during the Spring 2019 has also increased from 50% in January to over 60% now.
The Oceanic Niño Index (ONI), which is three months running mean of SST anomaly in the Niño 3.4 region, has further cemented the possibility of El Niño making a comeback. El Niño is declared when ONI is higher than or equal to 0.5°C for overlapping 3 months for five consecutive episodes. The most recent ONI value DJF (December – February) is 0.8°C.
The average value of oceanic Niño Index (ONI) taken over a period of three months for the last four consecutive episodes are as follows:
Even for the last episode of ONI, we expect temperatures to be in favour of El Niño. According to meteorologists, precursors are indicating that ONI value for JFM (January-March) as on March 13 is around 0.7°C. And with just two weeks to go, we do not expect much changes in the average temperature for the same period.
Impact on Monsoon 2019
El Niño is a very complex phenomena to explain and is quite famous for its notorious behavior. Particularly for sub-tropical region that bears the maximum impact of this phenomena, invariably linked with below normal rainfall during the Southwest Monsoon.
Any form of El Niño, be it a weak or strong, has potential to suppress the Monsoon rains. Based on January projections of declining El Niño probabilities, Skymet Weather had announced highest probability of normal Monsoon 2019 but chances of below normal rains also being bright.
However, scenario has now changed. As per the January projections, El Niño was showing a devolving trend with probabilities going below 50%. However, now models are predicting that chances of El Niño would be more than 50% at the time of onset of Southwest Monsoon 2019 but on the declining side. However, this decline process would be a gradual one.
Monsoon rains contribute over 70% of the annual rainfall for India. Being an agrarian nation, much is on stake on account of Monsoon rains, be it soil moisture, sowing, transplantation or irrigation of crops.
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