Knowledge Nugget | Hurricane Polo: What it tells us about tropical cyclones

Key Takeaways:

1. Tropical cyclones are known as hurricanes in the Caribbean Sea, the Gulf of Mexico, the North Atlantic Ocean and the eastern and central North Pacific Ocean.

2. A cyclone is a large-scale system of air that rotates around the centre of a low-pressure area. It is usually accompanied by violent storms and bad weather. As per National Disaster Management Authority (NDMA), a cyclone is characterised by inward spiralling winds that rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.  The NDMA classifies cyclones broadly into two categories: extratropical cyclones and tropical cyclones. 

Tropical cyclones (Hurricanes )

3. Tropical cyclones are those which develop in the regions between the Tropics of Capricorn and Cancer. They are the most devastating storms on Earth. Such cyclones develop when “thunderstorm activity starts building close to the centre of circulation, and the strongest winds and rain are no longer in a band far from the centre,” US National Oceanic and Atmospheric Administration (NOAA) noted.

4. The core of the storm turns warm, and the cyclone gets most of its energy from the “latent heat” released when water vapour that has evaporated from warm ocean waters condenses into liquid water, the agency added. Moreover, warm fronts or cold fronts aren’t associated with tropical cyclones.

5. Tropical cyclones have different names depending on their location and strength. For instance, they are known as hurricanes in the Caribbean Sea, the Gulf of Mexico, the North Atlantic Ocean and the eastern and central North Pacific Ocean. In the western North Pacific, they are called typhoons.

Extratropical cyclones

6. Also known as mid-latitude cyclones, extratropical cyclones occur outside of the tropic. They have “cold air at their core, and derive their energy from the release of potential energy when cold and warm air masses interact”, according to the US NOAA. 

7. Such cyclones always have one or more fronts — a weather system that is the boundary between two different types of air masses. One is represented by warm air and the other by cold air — connected to them, and can occur over land or ocean. 

Why did Polo intensify so quickly?

8. One factor scientists are examining is El Niño, the naturally occurring climate pattern marked by unusually warm surface waters in the central and eastern tropical Pacific. This year’s El Niño is unusually strong and is expected to strengthen further.

9. The World Meteorological Organization said in its September update that there is an almost 100 per cent likelihood that El Niño will persist through February 2027. It expects the event to intensify to a very strong level in the coming months, with its peak towards the end of 2026.

10. AP quoted Philip Klotzbach, a research scientist at Colorado State University, as saying El Niño had provided favourable conditions for Polo’s rapid intensification, with warmer Pacific waters and wind patterns creating many of the ingredients needed for a powerful storm.

11. But El Niño should not be presented as the sole cause of Polo. Tropical cyclones depend on multiple oceanic and atmospheric conditions, and the precise contribution of individual factors to one storm can be difficult to establish.

Why Polo’s development is important?

12. Polo’s development is particularly important because the Atlantic hurricane season has had the opposite experience. According to AP, no Atlantic hurricane had formed by Tuesday, making 2026 the slowest start to an Atlantic hurricane season on record. El Niño can increase wind shear over the Atlantic, making it harder for tropical systems to strengthen.

13. The bigger concern is what the unusually strong El Niño could mean for global temperatures, rainfall, drought and food and water security.

14. The WMO says a very strong El Niño can significantly alter rainfall and temperature patterns across many regions, increasing the likelihood of extreme weather. It cautions, however, that the strength of El Niño alone does not determine how severe the effects will be in any individual country. Other climate drivers, including conditions in the Indian and Atlantic oceans, can modify its impact.

BEYOND THE NUGGET: What is ‘Landfall’ of a cyclone?

1. Simply put, landfall is the event of a tropical cyclone coming onto land after being over water. As per the India Meteorological Department (IMD), a tropical cyclone is said to have made landfall when the centre of the storm – or its eye – moves over the coast.

2. Crucially, a landfall should not be confused with a ‘direct hit’, which refers to a situation where the core of high winds (or eyewall) comes ashore but the centre of the storm may remain offshore. As per the US NOAA, because the strongest winds in a tropical cyclone are not located precisely at the centre, it is possible for a cyclone’s strongest winds to be experienced over land even if landfall does not occur.

3. The damage caused by the landfall depends on the severity of the cyclone, marked by the speed of its winds. If the cyclonic storm is “very severe”, the impact may include extensive damage to kutcha houses, partial disruption of power and communication lines, minor disruption of rail and road traffic, potential threat from flying debris and flooding of escape routes. The factors behind this kind of damage include extremely strong winds, heavy rainfall and storm surges, which cause devastating floods on the coast.

4. Landfalls can last for a few hours, with their exact duration depending on the speed of the winds and the size of the storm system. Notably, cyclones lose their intensity once they move over land because of a sharp reduction in moisture supply and an increase in surface friction. This means that while landfalls are often the most devastating moments of cyclones, they also mark the beginning of their end.

Post Read Question

Which of the following are the consequences of the higher ocean temperatures?

1. Ocean stratification

2. Marine heat waves

3. Intense storms like hurricanes and cyclones

4. Higher rate of evaporation

Select the correct answer using the codes given below:

(a) 1 and 2 only

(b) 2, 3 and 4

(c) 2 and 4 only

(d) 1, 2, 3 and 4

Answer Key

(d)

(Sources: UPSC Issue at a Glance | Decoding Cyclones: Formation, Naming and Climate Change Linkages,  Visual graphics: Hurricane Polo turns Category 5. Why the world is watching El Niño)

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