Tornadoes

Context:

In recent years, many tornadoes have formed across India due to warming Bay of Bengal

Tornadoes:

• Tornadoes – Land-based vertical column of violently rotating air that extends from thunderstorm to ground.
• Origin –
  • Tornado formation typically needs 4 ingredients: Shear, Lift, Instability, and Moisture.
  • When there is wind shear, sometimes the winds begin to roll into a horizontal column of air.
  • Once there is a strong updraft of air being transported from the ground to the atmosphere, that column of air becomes vertical. That is when a storm usually develops in this scenario.
  • As the storm develops, it turns into a supercell thunderstorm. Supercells are storms that rotate and spin.
  • With both the vertical, rotating column of air and the supercell thunderstorm together, that may bring down a tornado from the storm cloud.

• Seasonal variations – Most common in spring and least common in winter. 
• Mostly occurred in – United States, Argentina and Bangladesh.
• Tornadoes in India – Reported in Eastern states of West Bengal, Odisha, and Jharkhand during pre-monsoon period.
  • However, Tornadoes, unlike cyclones, have a relatively low frequency of occurrence in India.

Tropical Cyclones and Tornadoes:

Parameters	Tropical Cyclones	Tornadoes
Size and Scale	Can span hundreds of miles and affect vast areas	Size is only a few hundred yards in diameter.
Wind Shear	Require very low values of tropospheric vertical shear.	Require substantial vertical shear of horizontal winds.
Temperature Gradient	Generated in regions of near-zero horizontal temperature gradient.	Produced in regions of large temperature gradient.
Area of Formation	Purely an oceanic phenomenon	Primarily developed over land.
Time-Scale	Lifetime that is measured in days	Typically lasts on the scale of minutes
Impact	Heavy rainfall, storm surges, and widespread flooding	Cause Localized destruction.

Source: The Indian Express

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Previous Year Question

Consider the following statements:
1. Jet streams occur in the Northern Hemisphere only.
2. Only some cyclones develop an eye.
3. The temperature inside the eye of a cyclone is nearly 10°C less than that of the surroundings.
Which of the statements given above is/are correct?

[UPSC Civil Service Exam – 2020 Prelims]

(a) 1 only
(b) 2 and 3 only
(c) 2 only
(d) 1 and 3 only

Answer: (c)
Explanation:
Statement 1 is incorrect. Jet streams occur both in the Northern Hemisphere as well as in the Southern Hemisphere.
Statement 3 is incorrect. The eye is the region of lowest surface pressure and warmest temperatures.

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