But what exactly caused it?

Scientists studying the event identified several important factors that helped the system develop and intensify.

1. It Started as a Weather Disturbance

The story began with a tropical atmospheric disturbance.

According to IMD research, a disturbance moved westward from the South China Sea region, crossed the Malay Peninsula and reached the Andaman Sea.

There, the system developed into a low-pressure area and subsequently intensified into a depression.

It then continued strengthening as it moved towards the southern Indian region.

So the cyclone did not suddenly form over Dhanushkodi.

It had already begun developing over the ocean several days earlier.

2. Why Did It Become Stronger?

One of the most interesting features of the 1964 storm was its rapid intensification at an unusually low latitude.

The IMD’s historical analysis found that the system intensified while located close to 5°N latitude.

Cyclone formation at such a low latitude is unusual because the Coriolis effect—which helps tropical cyclones develop their rotating circulation—is weaker near the equator.

This made the 1964 event particularly interesting to meteorologists.

3. The Warm Ocean Supplied Energy

A tropical cyclone needs a source of energy.

That energy largely comes from a warm tropical ocean.

Warm seawater increases evaporation, putting more water vapour into the atmosphere.

As moist air rises inside a developing storm, water vapour condenses into clouds and releases latent heat.

That heat warms the surrounding air and helps maintain the storm’s circulation.

The basic process can be simplified as:

Warm ocean → evaporation → moist air → rising air → condensation → heat release → stronger storm

This is one of the fundamental physical mechanisms behind tropical cyclone development.

4. Atmospheric Conditions Also Helped

Ocean temperature alone does not create a powerful cyclone.

The atmosphere must also provide suitable conditions.

The IMD’s study of the December 1964 storm identified upper-level divergence and an easterly trough as important features associated with its development.

In simple terms, air was able to move outward at higher levels of the atmosphere.

This helped air continue rising from the lower atmosphere.

As more air rose near the storm’s centre, the surface circulation could strengthen further.

Therefore, the cyclone developed because several favourable atmospheric and oceanic conditions occurred together.

5. Why Was the Sea So Dangerous?

The cyclone’s danger was not caused only by its wind.

A major threat came from the storm surge and extreme storm waves.

A storm surge occurs when strong winds and low atmospheric pressure associated with a cyclone cause seawater to pile up towards the coast.

Dhanushkodi was especially vulnerable because it was situated on a very low-lying and exposed coastal strip.

The IMD’s historical study estimated storm waves of approximately 5–6 metres above sea level in parts of the affected region.

This meant that enormous quantities of seawater could move across the narrow land.

The geography of Dhanushkodi therefore turned a powerful cyclone into a catastrophic coastal disaster.

6. Was It a Tsunami?

No.

This distinction is important.

The 1964 Dhanushkodi disaster was caused by a severe tropical cyclone and the associated storm waves and storm surge, not by the type of earthquake-generated tsunami commonly associated with major undersea earthquakes.

The historical IMD research specifically studied the cyclone and the storm waves produced by it.

So describing the event simply as a “giant wave” can be misleading.

The water was part of a much larger cyclone-driven coastal flooding process.

7. Why Did It Seem to Happen Suddenly?

This is perhaps the most interesting question.

The cyclone itself did not develop in a few minutes.

Meteorologically, the system developed over several days.

However, people in 1964 did not have today’s satellite observation, numerical weather prediction and modern warning systems.

A storm developing far over the ocean could therefore become a serious threat before people on the coast fully understood its intensity and trajectory.

Modern meteorologists can continuously monitor tropical systems using satellites, radar, computer models and other observations.

In 1964, those capabilities were far more limited.

So from the perspective of people on the ground, the cyclone could appear frighteningly sudden even though the atmospheric system had been developing for days.

What Scientists Actually Say

The scientific explanation is not that one mysterious factor suddenly created the Dhanushkodi cyclone.

Instead, the evidence points to a combination of conditions:

Atmospheric disturbance
↓
Low-pressure system
↓
Depression
↓
Favourable atmospheric conditions
↓
Warm ocean supplying energy
↓
Rapid intensification
↓
Severe cyclone
↓
Extreme storm waves and storm surge

That combination ultimately produced the catastrophic conditions around Dhanushkodi.

The Most Interesting Scientific Fact

Perhaps the most surprising part of the 1964 event is that the cyclone became very intense at an unusually low latitude.

Scientists studying the storm have therefore considered the event meteorologically unusual, not simply another ordinary tropical cyclone.

The disaster shows how a relatively small atmospheric disturbance can evolve into a major cyclone when the ocean and atmosphere provide the right conditions.

In one sentence:

The Dhanushkodi cyclone happened because an atmospheric disturbance encountered favourable tropical ocean and atmospheric conditions that allowed it to rapidly intensify into a severe cyclone, whose enormous storm waves and surge overwhelmed the low-lying coast.

And that is the scientific answer to the question:

Dhanushkodi was not destroyed by a mysterious wave—the disaster was the final result of a cyclone that had been building over the ocean through a chain of physical processes.

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