MPSC 2025 Prelims Paper-I · Question 25 of 100

Correct — option (4), 'Only b and d.' Statement d fails outright: in the Northern Hemisphere, air circulating into a low-pressure system, which is what a tropical cyclone is, is deflected to its right by the Coriolis force, which produces an anticlockwise (counterclockwise) rotation around the low, not a clockwise one — clockwise rotation is the Southern Hemisphere's pattern. Statement b overstates the standard figure for cyclone size. India Meteorological Department reference material describes a tropical cyclone as a vast, violent whirl typically 150 to 800 km across; the option's claimed range of '300 to 1500 km and even more' both raises the floor above what IMD gives as the lower end and nearly doubles the usual upper bound, so it does not match the standard figure used in Indian meteorological sources and is marked not correct here. Statements a and c, by contrast, hold up: tropical cyclones form within roughly 5° to 30° latitude of the equator in both hemispheres (never closer than about 5°, because the Coriolis force needed to spin up a vortex is too weak nearer the equator), which is squarely what statement a's '30° latitude region North and South of the equator' is describing; and IMD's own wind-speed classification opens the 'cyclonic storm' category at 34 knots (about 62 km/h) and only intensifies from there through severe, very severe, extremely severe and super cyclonic storm categories, so statement c's '50 to 60 km per hour and even more' sits at the right order of magnitude for a system on the threshold of becoming a cyclone and beyond. With a and c standing and b and d both failing, option (4) is the only choice that isolates exactly the pair that is wrong.

• (1)Only a — Statement a is not the false one — it correctly locates tropical cyclone formation within roughly the tropical belt bounded by about 30° latitude on either side of the equator (more precisely 5°–30°, since the zone within 5° of the equator lacks enough Coriolis force to spin up a cyclone). Selecting only statement a as incorrect misses the two statements — b and d — that actually contain errors, on cyclone diameter and rotation direction respectively.
• (2)Only b and c — This correctly flags statement b's overstated diameter figure but wrongly adds statement c to the list. Statement c's wind-speed range of '50 to 60 km per hour and even more' is close to the threshold India Meteorological Department uses to classify a system as a cyclonic storm (34 knots, about 62 km/h, and rising through more severe categories beyond that), so it is not a false statement — the false pair is b and d, not b and c, since this option omits statement d's rotation-direction error entirely.
• (3)Only d — This correctly identifies statement d's rotation-direction error but misses statement b's diameter error. Standard reference figures put a tropical cyclone's diameter at roughly 150 to 800 km, not the '300 to 1500 km and even more' claimed in statement b, so b is also a false statement and must be included alongside d — picking only d leaves one of the two actual errors unflagged.

A tropical cyclone is an intense, rotating low-pressure system that develops over warm tropical oceans (sea-surface temperature typically above 26–27°C), drawing energy from the latent heat released as moist air condenses around its centre. Three of its defining physical parameters recur across exam questions: the latitude band where it can form (roughly 5°–30° North and South of the equator, since the Coriolis force is too weak within about 5° of the equator to start a rotating system), its typical size (India Meteorological Department gives 150–800 km diameter as the standard range), and its rotation direction, which the Coriolis force fixes as anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere — the opposite of what many candidates instinctively guess.

MPSC builds this kind of 'which statements are not correct' item specifically to test whether a candidate has memorised precise reference figures rather than a vague general impression of cyclones. The rotation-direction trap (d) is a classic and frequently repeated error to guard against, since it inverts a fact many candidates otherwise know correctly for hurricanes reported in Western media (which are Northern Hemisphere storms, so getting the direction backwards here is a genuine, testable mistake). The diameter trap (b) is subtler: '300 to 1500 km' sounds plausible and is in the right general order of magnitude, which is exactly what makes it a good distractor against a candidate who has not fixed the specific IMD figure of 150–800 km in memory.

• Tropical cyclones form within roughly 5°–30° latitude North and South of the equator; within about 5° of the equator, Coriolis force is too weak to start the rotation.
• India Meteorological Department reference material gives a typical tropical cyclone diameter of 150 to 800 km, not the higher range sometimes quoted informally.
• In the Northern Hemisphere, tropical cyclones rotate anticlockwise (counterclockwise) around their low-pressure centre; in the Southern Hemisphere, they rotate clockwise — both are consequences of the Coriolis force.
• IMD classifies a system as a 'cyclonic storm' once sustained wind speed reaches 34 knots (about 62 km/h), rising through severe, very severe, extremely severe and super cyclonic storm categories as wind speed increases further.
• Tropical cyclones need a sea-surface temperature of roughly 26–27°C or higher to form and sustain themselves, drawing their energy from the latent heat of condensation in rising moist air.

• Assuming tropical cyclones rotate the same way in both hemispheres, or guessing the Northern Hemisphere direction backwards as clockwise
• Accepting a diameter or wind-speed figure because it 'sounds about right' rather than checking it against the standard IMD reference range
• Confusing the outer latitude limit of cyclone formation (about 30°) with the inner limit near the equator (about 5°), and describing the formation zone as starting at the equator itself

MPSC's climatology questions on tropical cyclones tend to bundle several precise, memorisable parameters — latitude band, diameter, wind speed thresholds, rotation direction — into a single multi-statement item, exactly as here, rather than asking about any one of them in isolation. The efficient way to prepare is to fix each parameter as a specific number or range (5°–30° latitude, 150–800 km diameter, 62 km/h cyclonic-storm threshold, anticlockwise in the Northern Hemisphere) rather than a loose qualitative sense of 'tropical cyclones are big, fast, rotating storms', since that loose sense is exactly what a plausible-sounding wrong figure like '300 to 1500 km' is designed to catch.

No directly related past PYQ was found.

• practice — not a real PYQ

  In which direction do tropical cyclones rotate around their centre in the Southern Hemisphere ?

  • (a)Anticlockwise (counterclockwise)
  • (b)Clockwise
  • (c)They do not rotate in the Southern Hemisphere
  • (d)The direction varies randomly by storm

  Answer(b) Clockwise — the Coriolis force deflects moving air to the left in the Southern Hemisphere, producing clockwise rotation around a low-pressure centre there, the opposite of the anticlockwise rotation seen in the Northern Hemisphere.

• practice — not a real PYQ

  As per India Meteorological Department's standard reference figures, the typical diameter of a tropical cyclone falls in which range ?

  • (a)50 to 100 km
  • (b)150 to 800 km
  • (c)1000 to 2000 km
  • (d)2500 to 3000 km

  Answer(b) 150 to 800 km — this is the range India Meteorological Department's own reference material gives for a tropical cyclone's diameter, describing it as a vast, violent whirl of that size.