2020 Indian Monsoon Season Is Off To A Strong Start

Written by on July 4, 2020 in Asia, Rest of World with 0 Comments

The 2020 Indian monsoon season has gotten off to a strong start thanks to the developing La Nina in the Pacific, favourable Madden Julian Oscillation and warmer than normal waters over the Indian Ocean. In fact we have seen very high rainfall totals across many areas of India already and we’re just a month in. The typically later northern areas have seen big rain amounts during the later half of June. Ahead of schedule.

Average arrival of the monsoon.

Date of monsoon covering entire country:

2012: July 11

2013: June 16

2014: July 17

2015: June 26

2016: July 13

2017: July 19

2018: June 28

2019: July 19

2020: June 26

(News Reports; IMD)

What is the monsoon and how does it work?

Put in simple terms.

Monsoon is an Arabic word meaning ‘season’. A seasonal shift in winds. During the spring months, the Indian land mass and Tibetan plateau heat forcing the lowering of atmospheric pressure. Temperatures widely peak at between 40-47C throughout India during May. The northwest corner of India and Pakistan typically exceeds 50C.

As India heats and atmospheric pressure lowers, so pressure rises over the warm Indian Ocean and therefore air is pulled from the ocean towards India.

The intertropical convergence zone (ITCZ) lifts north with the sun and through the Indian Ocean. This convective belt and southwest/southeast winds interact meet the ITCZ creating the ‘monsoon trough’.

Winds blow strong thanks to temperature and pressure imbalance between land and ocean. Vast amounts of water get lifted into the atmosphere.

Credit: Tropical Tidbits

By the time this heavy moisture laden air has reached the shores of Kerala on the southern tip of India, vast thunderstorm clouds have formed and these dump big amounts of rain, especially so when this moisture laden air bumps into the Western Ghats (mountains) and is forced to rise, cool and condense. This orographic lift enhances the rainfall.

Image via Skymetweather

Why are the Himalayan foothills amoung the wettest places on earth?

At the peak of the season, the ITCZ reaches it’s northernmost position, the Himalayas, where it cannot climb over and communities here, in the high foothills see the greatest rainfall on earth due the stalling of the tropical conveyor belt combined with orographic lift.

Why the early and energetic start this year?

There are several factors which can explain this good start.

  1. Waters in the Indian Ocean are warm with a neutral Indian Ocean Dipole (IOD).
  2. Waters north of Madagascar are warmer than normal which helps enhance the high pressure system and amount of moisture lifted into the atmosphere over the western Indian Ocean basin.
  3. The current Madden Julian Oscillation (MJO) is in an enhanced phase over E Africa and W Indian Ocean which combined with ‘warmer than normal SST’s’ fuel moister, stronger SW monsoon winds.
  4. Waters in the east equatorial Pacific are cooling which also enhances the monsoon pattern.

During El Nino, the monsoon is weaker. During La Nina, monsoons tend to be stronger.

As you can see from the below SSTA map of the Indian Ocean, we have a neutral Indian Ocean Dipole (IOD) and particularly warm waters just off north/northeast Madagascar.

Credit: Tropical Tidbits

June alone has seen some spots in the western ghats exceed 2,000mm.

Credit: Vagaries of the Weather

A LOT of rain to come over the next 2 weeks.

Credit: Tropical Tidbits

CFSv2 weekly precipitation anomaly

wk 1

Credit: Tropical Tidbits

wk 2

Credit: Tropical Tidbits

wk 3

Credit: Tropical Tidbits

wk 4

Credit: Tropical Tidbits

Tags: ,

Follow us

Connect with Mark Vogan on social media to get notified about new posts and for the latest weather updates.

Subscribe via RSS Feed Connect on YouTube

Leave a Reply