Tropical Cyclones Questions and Answers

Q: Tropical cyclones usually do not form close to the Equator primarily because

The main reason is that the Coriolis force is too weak.A tropical cyclone needs the inflowing air to be deflected into a rotating vortex. The Coriolis parameter \(f = 2\Omega\sin\phi\) is zero at the Equator and very small within about 5° of it, so converging air flows straight in and fills the low instead of spinning up; cyclones therefore rarely form there.The equatorial sea surface is warm, not too cold. Weak vertical wind shear favours cyclones rather than preventing them, and the beta effect influences cyclone drift, not cloud dissipation.

Q: Which one of the following is the main reason why tropical cyclones rarely form over the Bay of Bengal during the summer monsoon season?

The main reason is strong vertical wind shear.During the summer monsoon, low-level westerlies blow over the Bay of Bengal while the tropical easterly jet blows strongly in the upper troposphere. The large change in wind with height tilts and tears apart developing convective systems and carries away the heat that a warm-core vortex needs to build up. Disturbances therefore usually remain monsoon depressions rather than becoming cyclones. Cyclones over the Bay peak in the pre-monsoon and post-monsoon seasons, when the shear is weak.The other reasons do not apply in this season: the monsoon trough supplies strong low-level cyclonic vorticity, the mid-troposphere is moist, and the atmosphere is convectively unstable.

Q: A low pressure system is said to be a cyclonic storm if the wind speed exceeds :

A system is a cyclonic storm when the wind speed exceeds 33 knots.The India Meteorological Department classifies low pressure systems by maximum sustained wind: depression 17-27 knots, deep depression 28-33 knots, and cyclonic storm 34-47 knots, followed by severe cyclonic storm and higher categories. So a cyclonic storm is one whose winds exceed 33 knots.17 knots marks the start of a depression and 27 knots its upper limit, while 24 knots lies within the depression range. None of them is the cyclonic storm threshold.

Q: Which among the following is correct for a tropical cyclone ?

In a tropical cyclone the vertical pressure gradient is larger than the horizontal pressure gradient.Even in a cyclone the atmosphere stays close to hydrostatic balance. Pressure falls by about 1 hPa for every 8-10 m of height, that is roughly 100 hPa per km vertically, while the steepest horizontal gradient near the eyewall is of the order of a few hPa per km. The vertical gradient is therefore much larger.So the horizontal gradient is not larger, the two are not nearly equal, and the vertical gradient is never zero, since it balances gravity.

Q: Tropical storms (cyclones) over the Bay of Bengal & the Arabian Sea have a bimodal frequency having peaks during :

The peaks are in March-May and October-November.Tropical cyclones over the North Indian Ocean have a bimodal season: a pre-monsoon peak in April-May and a stronger post-monsoon peak in October-November. During the monsoon itself (June-September) strong vertical wind shear stops depressions from deepening into severe cyclones, and in winter the sea is cooler.January-February and December-January are the quiet winter months, and July-August falls in the monsoon, when monsoon depressions rather than cyclonic storms are the typical systems. Only the March-May and October-November pair spans both peaks.

Q: According to Dvorak classification T3.5 represents :

T3.5 represents a tropical cyclone of tropical storm strength.In the Dvorak technique a T-number estimated from satellite cloud patterns is converted to a maximum wind. T3.5 corresponds to about 55 knots, within the 34 to 63 knot range of a tropical storm, that is a named tropical cyclone (a severe cyclonic storm in the Indian scale).A tropical depression is below T2.5 (under 35 knots). Hurricane strength, 64 knots and above, begins at T4.0, so Category 1 starts there and Category 2 corresponds to about T5.0, both above T3.5.

Tropical cyclones usually do not form close to the Equator primarily because

A.sea surface temperature at the Equator is too cold.
B.beta effect dissipates clouds.
C.Coriolis force is too weak.
D.vertical shear of the zonal wind is weak.

Exam Year(s)

GATE XE - 2022,

Answer: C

The main reason is that the Coriolis force is too weak.

A tropical cyclone needs the inflowing air to be deflected into a rotating vortex. The Coriolis parameter \(f = 2\Omega\sin\phi\) is zero at the Equator and very small within about 5° of it, so converging air flows straight in and fills the low instead of spinning up; cyclones therefore rarely form there.

The equatorial sea surface is warm, not too cold. Weak vertical wind shear favours cyclones rather than preventing them, and the beta effect influences cyclone drift, not cloud dissipation.

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Which one of the following is the main reason why tropical cyclones rarely form over the Bay of Bengal during the summer monsoon season?

A.Strong vertical wind shear.
B.Weak low-level relative vorticity.
C.Dry mid-troposphere.
D.Stable atmosphere.

Exam Year(s)

GATE XE - 2025,

Answer: A

The main reason is strong vertical wind shear.

During the summer monsoon, low-level westerlies blow over the Bay of Bengal while the tropical easterly jet blows strongly in the upper troposphere. The large change in wind with height tilts and tears apart developing convective systems and carries away the heat that a warm-core vortex needs to build up. Disturbances therefore usually remain monsoon depressions rather than becoming cyclones. Cyclones over the Bay peak in the pre-monsoon and post-monsoon seasons, when the shear is weak.

The other reasons do not apply in this season: the monsoon trough supplies strong low-level cyclonic vorticity, the mid-troposphere is moist, and the atmosphere is convectively unstable.

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A low pressure system is said to be a cyclonic storm if the wind speed exceeds :

A.17 knots
B.24 knots
C.27 knots
D.33 knots

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: D

A system is a cyclonic storm when the wind speed exceeds 33 knots.

The India Meteorological Department classifies low pressure systems by maximum sustained wind: depression 17-27 knots, deep depression 28-33 knots, and cyclonic storm 34-47 knots, followed by severe cyclonic storm and higher categories. So a cyclonic storm is one whose winds exceed 33 knots.

17 knots marks the start of a depression and 27 knots its upper limit, while 24 knots lies within the depression range. None of them is the cyclonic storm threshold.

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Which among the following is correct for a tropical cyclone ?

A.Horizontal pressure gradient is larger than vertical pressure gradient
B.Vertical pressure gradient is larger than horizontal pressure gradient
C.Both are nearly equal
D.Vertical pressure gradient is zero

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

In a tropical cyclone the vertical pressure gradient is larger than the horizontal pressure gradient.

Even in a cyclone the atmosphere stays close to hydrostatic balance. Pressure falls by about 1 hPa for every 8-10 m of height, that is roughly 100 hPa per km vertically, while the steepest horizontal gradient near the eyewall is of the order of a few hPa per km. The vertical gradient is therefore much larger.

So the horizontal gradient is not larger, the two are not nearly equal, and the vertical gradient is never zero, since it balances gravity.

Discuss in Forum

Tropical storms (cyclones) over the Bay of Bengal & the Arabian Sea have a bimodal frequency having peaks during :

A.Jan.-Feb. & March-May
B.Dec.-Jan & March-April
C.March-May & Oct.-Nov
D.July-August & April-May

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: C

The peaks are in March-May and October-November.

Tropical cyclones over the North Indian Ocean have a bimodal season: a pre-monsoon peak in April-May and a stronger post-monsoon peak in October-November. During the monsoon itself (June-September) strong vertical wind shear stops depressions from deepening into severe cyclones, and in winter the sea is cooler.

January-February and December-January are the quiet winter months, and July-August falls in the monsoon, when monsoon depressions rather than cyclonic storms are the typical systems. Only the March-May and October-November pair spans both peaks.

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According to Dvorak classification T3.5 represents :

A.Tropical Depression
B.Tropical Cyclone
C.Cat 1 Hurricane
D.Cat 2 Hurricane

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: B

T3.5 represents a tropical cyclone of tropical storm strength.

In the Dvorak technique a T-number estimated from satellite cloud patterns is converted to a maximum wind. T3.5 corresponds to about 55 knots, within the 34 to 63 knot range of a tropical storm, that is a named tropical cyclone (a severe cyclonic storm in the Indian scale).

A tropical depression is below T2.5 (under 35 knots). Hurricane strength, 64 knots and above, begins at T4.0, so Category 1 starts there and Category 2 corresponds to about T5.0, both above T3.5.

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