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| India's Southwest Monsoon 2020 Will Average At least 99-101% Rainfall in India, Says Accuweather Senior Meteorologist - Jason Nicholls |
India:
The Southwest Monsoon Season is the main rainy season of the Indian Subcontinent. The Southwest Monsoon as its dominance over the whole country during June-September. It gives around 75% of the annual rainfall over the whole country during this period.
The Southwest Monsoon Season in India official begins from 1st June and last till 30th Septemeber that consists of four months (June, July, August, September). The month of June is an onset month, whereas the month of July and August are the two core months of the four-month-long monsoon season, while the month of September is a withdrawal month.
The Onset of Monsoon is declared when there is a sudden increase in the rainfall activity, it first hits the extreme southwestern tip of the country by the end of May or start of June and then progresses inland in phases and covers the entire country by the middle of the month of July.
The withdrawal of the monsoon starts from the extreme northwestern region of the country. In comparison with the onset process, the withdrawal process takes a long time.
Highlights:
- India's Monsoon Rainfall 2020 will average at least near normal i.e 99-101%.
- The onset date of Monsoon to be around 1st June(+/- 5).
- The Official Monsoon forecast to be released in April.
Jason Nicholls says they were watching several teleconnections to operate up the forecast.
1) Eurasian Snowcover:
He said whenever there Is below normal snow cover from late winter into spring it usually means good monsoon for the country. He noted that the February 2020 snow cover anomalies were at the third-lowest level only behind 2002 and 1995. He also stated that the seasonal 2019-2020 snow cover was lowest since 2007. Thus the first teleconnection is in the favor of good monsoon this season.
It is a measure of the winds in the stratosphere, he said that the paper shows the easterly (negative) QBO at 15 mb during winter means weakened monsoon, whereas during monsoon the easterly QBO at 50 mb means a weak monsoon. In winter this QBO value at 15 mb was ranging between (-265) to (-323). This indicates the winds were easterly, he also mentioned that we will be watching this factor closely. Thus the second teleconnection is right now not in the favor of the good monsoon season.
3) IOD(Indian Ocean Dipole):
IOD is an irregular oscillation of sea surface temperature in which the western part of the Indian Ocean becomes alternately warmer and then cooler than the eastern part of the ocean. when both sides have close to the average temperature then it is called neutral IOD.
The +ve IOD leads to a wetter monsoon season. The year 2019 saw the strongest +ve Indian ocean Dipole(IOD) that caused above normal rainfall in the country. The country saw 110% rainfall of LPA(Long Period Average), Most major models in the world were predicting below normal rainfall in the country due to the occurrence of El-Nino, but this +ve IOD reversed the condition and gave 110% rainfall highest since past 25 years. He said that this Monsoon season the IOD is likely to remain neutral or turn weakly negative. He also states that this means the IOD we have no significant role in this monsoon season. Thus the third teleconnection is in the favor of near-normal monsoon.
4) ENSO(El-Nino Southern Oscillation):
ENSO means irregular periodic variations in winds and sea surface temperatures over the tropical eastern pacific ocean. El-Nino conditions typically mean below normal rainfall in the country during the monsoon season. He said that the ENSO will remain largely neutral into early summer and also signaled that La-Nina conditions can be developed late in 2020. La-Nina conditions are related to good summer monsoon rainfall in India. Thus the fourth teleconnection is in the favor of normal to above normal monsoon rainfall.
5) Sea Surface Temperature of Atlantic Ocean:
He said that warmer water in the Atlantic ocean leads to active and wetter Indian monsoon season, it gets enhanced when it is sync with ENSO. The Atlantic waters are expected to remain warmer than the normal signaling towards good monsoon season. Thus the fifth teleconnection is in the favor of good monsoon season.
Lastly, he stated that the overall seasonal monsoon rainfall will average at least near normal 99-101% of normal, onset date is likely to be around 1st June (+/- 5).
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