The Odd 2021
- According to data from the India Meteorological Department (IMD), the usual peak season for cyclones in India is October and November.
- This year, as many as 7 low-pressure areas (LPA) had been formed in the North Indian Ocean region since October 1, 2021 till mid November.
- However, none of them have intensified into a cyclone…!!!
- Surprise Surprise..!!
- If December 2021, also remains cyclone-free, it would be the first time since 1961 that the post-monsoon season would remain without a cyclone.
- This has happened only five times since 1891:
The Tropical Storms
Favourable conditions for Cyclones
- Continuous supply of Warm moist air
- Above 26 degree water temperature
- Coriolis force
- Absence of wind shear
- Pre existing Baroclinic instability
Read about: Cyclone Mandous
What has happened in 2021?
- At least 3 Low Pressure Areas were formed in October and 4 in November.
- A remnant of an one LPA that had formed in October in the Bay of Bengal entered the Arabian Sea on November 3 and re-intensified on November 6. This system further intensified into a depression on November 7. But the conditions in east-central Arabian Sea were not favourable for further intensification.
Then what was this?
Rains in AP, TN
- The depression formed on October 18 in Bay of Bengal and crossed over to land in the early hours of November 19. It caused torrents of rainfall along the Tamil Nadu and Andhra Pradesh coasts.
- Initially, the forecast for this system by the Global Forecasting System of the United States data had suggested it would intensify into a cyclone (Cyclone Jawad).
- But that did not happen…!!
- The IMD said that cyclone formation did not happen because of unfavourable land interactions of the system. In fact, when cyclones Gulab and Shaheen had formed successively around the end of September, it seemed like the cyclone season had started off.
- But that did not. Some scientists suggest that this is due to the impact of delayed summer monsoon rains. SW Monsoon Rains extending into October may have had a suppressing effect due to shear and energy dissipation.
- This year, monsoon finally retreated on October 26, 11 days later than the normal date of October 15. The extension of the monsoon rainfall may also be a reason for the lack of cyclones.