Maarg Manthan · Topic 8.9

Tropical Cyclones versus Temperate Cyclones

Geography › Storms, Cyclones, Jet Streams and Air Masses · Topic 8.9

Tropical and temperate cyclones are both low pressure systems with winds spiralling inward, but they differ in origin, energy source, structure, size, movement and season. A tropical cyclone forms over warm tropical seas, has an eye and draws energy from latent heat, while a temperate cyclone forms along fronts in the middle latitudes and draws energy from temperature contrast.

5 min read · UPSC Prelims · Geography · Storms, Cyclones, Jet Streams and Air Masses

At a Glance

Tropical origin Warm oceans, 5 to 20 degrees
Temperate origin Polar front, 35 to 65 degrees
Energy Latent heat versus temperature contrast
Eye Only in tropical cyclones
Movement East to west versus west to east
Exam link UPSC Prelims, Geography: Storms, Cyclones, Jet Streams and Air Masses

Where Does It Fit?

This is the ninth topic of the category on storms, cyclones, jet streams and air masses. The previous topics described tropical and temperate cyclones one by one, and this one sets them side by side. The last topic of the category covers the polar vortex. Previous topic: Temperate Cyclones. Next topic: Polar Vortex.

How Do Tropical and Temperate Cyclones Compare?

In short: a tropical cyclone is a compact heat engine over warm seas, and a temperate cyclone is a large wave on a front.

Basis	Tropical cyclone	Temperate cyclone
Region of origin	Warm tropical oceans, between about 5 and 20 degrees latitude	Middle and high latitudes, about 35 to 65 degrees, over land and sea
Cause and energy	Latent heat released by condensation of vapour from a warm sea	Contrast of temperature between air masses, and the jet stream aloft
Fronts	No fronts; air mass is uniform	Has a warm front, cold front and warm sector
Eye	Has a calm, clear eye	No eye
Size	Smaller: 300 to 1,500 km across	Larger: 1,000 to 3,000 km across
Wind speed	Very high; can exceed 200 km per hour	Usually moderate; less intense winds
Movement	From east to west in the tropics, then recurves	From west to east with the westerlies
Speed of movement	Slow: about 10 to 30 km per hour	Faster: 30 to 50 km per hour or more
Season	Late summer and autumn, when the sea is warmest	All year, but strongest in winter
Over land	Weakens and dies quickly	Can travel over land and sea
Duration	A few days to about two weeks	Several days to a week
Rain pattern	Intense rain in a small area, with spiral bands	Widespread, long rain over a large area
Main hazards	Storm surge, winds, flooding	Rain and snow, cold waves, floods, gales
Examples	Hurricanes, typhoons, Amphan, Fani	European windstorms, western disturbances

What Are the Main Similarities and Why Do the Differences Matter?

Both are areas of low pressure with winds that blow inward and upward in an anticlockwise spiral in the northern hemisphere and a clockwise spiral in the southern hemisphere, because of the Coriolis force. Both bring clouds, strong winds and heavy rain and both can cause serious damage. Yet the differences are crucial. The tropical cyclone is symmetric and warm-cored: it is warmest at its centre, and it needs the sea to keep going. The temperate cyclone is asymmetric and cold-cored, with fronts, and it needs the temperature gradient between air masses, as in Temperate Cyclones. A tropical cyclone can change into a temperate cyclone after it moves out of the tropics into the westerlies: this transition, called extratropical transition, often makes the storm larger and faster, and sometimes brings damaging winds to places such as Japan or western Europe. For the formation of the tropical storm, see Tropical Cyclones – Formation and Conditions.

How Should You Answer a Comparison Question?

Start with one line of definition: both are low pressure systems with cyclonic winds.
Use the table points that carry marks: origin, energy source, fronts, eye, size, direction of movement and season.
Add a hazard and India link: storm surge and coastal Odisha, Andhra Pradesh and West Bengal for tropical cyclones; western disturbances and winter rain for temperate ones.
Do not mix with tornadoes: a tornado is much smaller, with a width of hundreds of metres, forms from a thunderstorm, and lasts minutes, as in Tornadoes.

As an analytical point, the two storms point to two different risk systems: the tropical cyclone is a sudden, coastal hazard for which evacuation is the main response, while the temperate cyclone is a broad hazard of rain, snow and cold in which infrastructure and forecasting matter more. Climate change is expected to strengthen the intensity and rainfall of tropical storms, and to shift the mid-latitude storm tracks, so both storms are becoming more important in planning for resilience.

Why Is This Topic Important?

Format Comparison tables are common
Concepts Origin and energy asked
Application Hazard planning

What Came Next?

The last topic of the category describes the polar vortex, a very large circulation over the poles. Next topic: Polar Vortex.

Key People and Terms

Warm-core Warmest at the centre, as in tropical cyclones
Cold-core Coldest at the centre, as in temperate cyclones
Latent heat Energy from condensation
Front Boundary between air masses
Extratropical transition Tropical cyclone turning into a temperate one
Storm surge Sea rise driven by a tropical storm

Exam Corner

Points to Remember

Tropical: eye, no fronts, latent heat.
Temperate: fronts, no eye, temperature contrast.
Tropical cyclones move east to west at first.
Temperate cyclones move west to east.
Temperate cyclones are larger.

Do Not Confuse With

Warm-core and cold-core Tropical versus temperate
Eye and warm sector Calm centre versus warm wedge between fronts
Tornado and cyclone Metres wide versus hundreds of kilometres wide

Memory Hook

Tropical: warm sea, an eye, east to west; temperate: fronts, bigger, west to east.

Mains Angle

Questions ask for a clear comparison. These points add depth.

Energy Latent heat versus gradient
Structure Eye versus fronts
Link Extratropical transition

A Question You May Face

An original practice question, not a past paper question.

“Compare the origin, structure and effects of tropical and temperate cyclones with reference to India.”

How to Answer

Define Both are lows.
Compare Table of features.
India Coastal cyclones and western disturbances.
Change Climate and storm tracks.

GS Relevance

Prelims and Mains: comparison table of tropical and temperate cyclones, tornado and cyclone differences. GS Paper 1: climatology.

Frequently Asked Questions

What is the main difference between tropical and temperate cyclones?

A tropical cyclone forms over warm tropical oceans, has an eye and gets its energy from latent heat, whereas a temperate cyclone forms along fronts in the middle latitudes, has no eye and gets its energy from the temperature difference between air masses.

Which cyclone is larger, tropical or temperate?

The temperate cyclone is larger, usually 1,000 to 2,000 kilometres across and sometimes 3,000 kilometres, whereas a tropical cyclone is usually 300 to 1,500 kilometres across. However, the tropical cyclone has much stronger winds and a more intense rainfall near its centre.

Do temperate cyclones have an eye?

No, temperate cyclones do not have an eye. They have a warm sector between a warm front and a cold front, and their winds are strongest near the fronts. Only mature tropical cyclones have the calm, clear eye surrounded by a ring of intense winds.

In which direction do tropical and temperate cyclones move?

Tropical cyclones first move from east to west with the trade winds, and then often recurve to the poles. Temperate cyclones move from west to east with the westerlies, steered by the jet stream, at a faster speed than tropical ones.

Can a tropical cyclone become a temperate cyclone?

Yes. When a tropical cyclone moves into the middle latitudes, it can lose its warm core and acquire fronts, which is known as extratropical transition. The storm often grows larger and moves faster, and can still bring dangerous winds and rain, as when Pacific typhoons reach Japan.

PYQ Practice — Statement Analysis

1 A tropical cyclone has an eye, but a temperate cyclone does not.

True

Temperate cyclones have a warm sector instead.

2 Temperate cyclones draw their energy from latent heat of the warm sea.

False

They draw energy from temperature contrast.

3 Temperate cyclones are larger in area than tropical cyclones.