The document discusses the lack of cyclones forming in the North Indian Ocean region in October and November 2021, despite conditions generally being favorable for cyclones during this peak season. No clear reason for this anomaly has been identified, though some experts believe the late retreat of the monsoon may have inhibited cyclone development by acting as self-limiting factors. Further research is needed to fully understand the causes behind the absence of cyclones this season.

1. (1)
Why in news?
 As many as seven low-pressure areas (LPA) have formed in the North Indian Ocean region since October
1, 2021 — but none of them have intensified into a cyclone. This is unusual as October and November
constitute the peak cyclone season for India, according to data from the India Meteorological
Department (IMD).
o No cyclone formation in the rest of November would mean a first-time anomaly in the last 31
years for October and November.
o If December also remains cyclone-free, it would be the first time since 1961 that the post-monsoon
season would remain without a cyclone.
Why is this anomalous?
 This is happening despite the fact that the La Nina phase
of the El Nino Southern Oscillation (ENSO) phenomenon
is currently prevailing.
 The La Nina is the cooling phase of the ENSO and is
generally favourable for cyclone / hurricane / typhoon
formation all over the world, including in the North Indian
Ocean region.
 The North Atlantic Ocean experienced record storm and
hurricane activity due to the emergence of La Nina or due
to its potential emergence in the last two years. The
phenomenon creates an extended region of low vertical
wind shear, which is favourable for the intensification of
cyclones.
What is the possible reason?
 When cyclones Gulab and Shaheen had formed successively around the end of September, it seemed
like the cyclone season had started off. This had also come after the record-breaking formation of low-
pressure areas in September that continued in October and November and caused excessive rainfall and
floods in many parts of the country.
 The October floods in Kerala and Uttarakhand and the November floods in Tamil Nadu were caused
partly by low-pressure areas. Along with this, the southwest monsoon season extended into late
October.
 The monsoon finally retreated on October 26, 11 days later than the normal date of October 15.
Monsoon had even started retreating only on October 6. The extension of the monsoon rainfall
may be a reason for the lack of cyclones, according to experts.
 Its been observed that, low-pressure systems are only acting as self-inhibitors for strong cyclone
growth. This is possible reason for low cyclogenesis this year, as per the IMD
Why were there no cyclones in October and November this year?
Indian Meteorological Department (IMD):
• It is national meteorological service of the
country and chief government agency dealing
in everything related to meteorology,
seismology and associated subjects.
• It was formed in 1875.
• It functions under Ministry of Earth Sciences.
• It is headquartered in New Delhi.
History of IMD:
• Established in 1875 at Calcutta, by the British
Government.
• The first Director General of Observatories
was Sir John Eliot
The headquarters of IMD were later shifted to
Shimla, then to Poona (now Pune) and finally to
New Delh.
GUIDANCE
IAS

2. (2)
It is notable that, exact reason for this anomaly is not known, further research on this issue is required to
answer these questions.
Additional information:
What is a Tropical Cyclone?
 Tropical cyclones are low pressure systems that form over warm tropical waters. They typically form when the
sea-surface temperature is above 26.5°C. Tropical cyclones can continue for many days, even weeks, and may
follow quite erratic paths. A cyclone will dissipate once it moves over land or over cooler oceans.
 A more technical definition of a tropical cyclone is: “A non-frontal low pressure system of synoptic scale
developing over warm waters having organised convection and a maximum mean wind speed of 34 knots or
greater extending more than half-way around near the centre and persisting for at least six hours.”
How do tropical cyclones form?
 A cluster of thunderstorms can develop over
warm tropical oceans. If that cluster persists in an
area of low pressure, it can start rotating. If the
conditions are just right, the cluster of
thunderstorms can grow in size and sustain itself
and then develop into a tropical cyclone.
 Once developed, a tropical cyclone is like a giant,
atmospheric heat engine. The moisture from the
warm ocean acts as it's fuel, generating huge
amounts of energy as clouds form.
 The rotating thunderstorms form spiral rainbands
around the centre (eye) of the cyclone where the
strongest winds and heaviest rain are found (eye wall), transporting heat 15 km or higher into the
atmosphere. The drier cooler air at the top of the atmosphere becomes the exhaust gas of the heat engine.
 Some of the cool air sinks into the low-pressure region at the centre of the cyclone, hence causing the
relatively calm eye. The eye is usually about 40 km wide but can range from 10 to over 100 km, with light
winds and often clear skies. The rest of the cool air spirals outward, away from the cyclone centre, sinking in
the regions between the rainbands.
 As long as the environmental conditions support this atmospheric heat engine, the tropical cyclone can
maintain its structure and even intensify over several days.
GUIDANCE
IAS