Friday, March 10, 2023

9th March:

El Nino and The South West Monsoon...Instead of going into panic mode, let us first understand the  current phase and possibility of an "El Nino" situation.  

El-Nino:

El Niño refers to a warming of the central and eastern tropical Pacific Ocean that can have compounded effects on global weather patterns. El Niño events can have significant impacts on the SouthWest monsoon.


But, there is no one-to-one direct effect between El Niño and the Indian summer monsoon. The quantum of impact may vary depending on the strength and timing of the El Nino event.

Overall in history.👇
Data from 1951 shows there were 15 moderate and strong El Nino events between 1951 and 2022.

As per information form records, In this period, the Indian monsoon was deficient (-10%) in 8 years and in another 3 years the monsoon rainfall was on the lower side of the norm ( -5% to -10%).

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Technical Explanatory Note of Latest Scenario:

* La Niña has ended and ENSO-neutral conditions are expected to continue through the Northern Hemisphere spring (March/April)and early summer 2023.(May/June)(as per CPC)

*Equatorial sea surface temperatures (SSTs) are below average across most of the Pacific Ocean. 

*Niño 3.4 -0.2ºC

*The tropical Pacific atmosphere is consistent with La Niña. ENSO-neutral conditions are expected to begin within the next couple of months, and persist through the Northern Hemisphere spring and early summer.

**The ONI is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO. Defined as the three-month running-mean SST departures in the Niño 3.4 region.

 El Niño: characterized by a positive ONI greater than or equal to +0.5ºC. La Niña: characterized by a negative ONI less than or equal to -0.5ºC. By historical standards, to be classified as a full-fledged El Niño or La Niña episode, these thresholds must be exceeded for a period of at least 5 consecutive overlapping 3-month seasons. 

(CPC considers El Niño or La Niña conditions to occur when the monthly Niño3.4 OISST departures meet or exceed +/- 0.5ºC along with consistent atmospheric features. These anomalies must also be forecasted to persist for 3 consecutive months.)


The most recent ONI value (December 2022 – February 2023) is -0.7ºC.

Excerpts from National Oceanic and Atmospheric Administration (NOAA)

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Expected Position Explanation:(As per Vagaries)


A perfect forecast of El Nino and how it will impact the South West monsoon will be seen only by May-June. Besides El Nino, there are other factors too influencing monsoons. 

So, the earliest that an initial El Nino can be called as "setting" is in June/July 2023. 

But we should  now expect an full fledged El Nino event by August-September.

Let's be Alert rather than confused.




3 comments:

sset said...

Reports of severe heat wave from Kerala

sridu said...

Thanks Rajesh...

sset said...

El-Nino is good and blessing to some countries. For instance south america Peru, Argentina el-nino brings good rains due to warm waters over coast. Argentina for instance facing severe drought for 3 successive years due to triple la-nina. India own NEM is said to be better during el-Nino however various other influencing parameters.

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