EXCLUSIVE| Odisha On Alert: Another September 23-like System Brewing? Winds Signal Monsoon Exit from Oct 1, October Heat to Loom!

Bhubaneswar: The September 23 deep depression came, crossed the coast near Kalingapatnam, curved inland and marched across Odisha towards Chhattisgarh – leaving behind a trail of swollen rivers and flooding from the Vansadhara in the south to the Jalka and Budhabalanga in the north, while Cuttack continues to grapple with the lingering impact of the Mahanadi waters.

The waters from that system are yet to completely recede. But even as Odisha is still dealing with the after-effects, the weather map has begun writing another story over the Bay.

A fresh cyclonic circulation is taking shape over Thailand and is expected to move towards the Andaman Sea, immediately raising the question: could September 23 be replayed in October?

The answer, at least from the present atmospheric configuration, is more nuanced.

The weather is entering one of its most dynamic phases of the year. The monsoon circulation is weakening, continental winds are beginning to push into the Indian subcontinent and the Bay of Bengal is entering the post-monsoon transition zone. At the same time, the Pacific is in a strengthening El Niño phase, with NOAA's September assessment putting the probability of El Niño during the September-November and October-December periods at effectively 100%, while warning of an exceptionally strong event.

That combination is producing a major change in the wind architecture over India, the Arabian Sea and the Bay of Bengal.

And that could determine the fate of the next system – as well as the character of Odisha's October.

Will Odisha record another cyclone genesis?

The new circulation over Thailand and its projected movement towards the Andaman Sea certainly deserves watching, particularly because the previous September system also emerged from the broader Southeast Asia–Andaman Sea corridor before reaching the Bay.

But the present atmospheric setup is markedly different.

The emerging circulation is moving into a changing wind field, with increasingly prominent northerly and northwesterly continental winds spreading south and east from the Indian landmass. These winds are progressively replacing the moisture-laden southwesterly monsoon flow.

That creates a fundamental problem for any developing tropical system.

A system entering the Bay requires a sufficiently moist environment, organised low-level convergence and favourable upper-air conditions to consolidate. If the continental dry-air intrusion and changing wind field remain dominant, the circulation can be sheared, weakened or pushed towards the Myanmar side rather than developing into an organised system moving towards Odisha.

The present model sequence described in the weather maps therefore does not yet indicate a repeat of the September 23 deep depression, let alone establish a fresh Odisha-bound cyclone.

In fact, the projected evolution points towards the circulation becoming increasingly confined to the Myanmar–Andaman–eastern Bay sector and weakening as it encounters the changing large-scale flow.

That, however, does not mean the Bay has become harmless.

October is a classic transition month for the Bay of Bengal. Once the southwest monsoon retreats, the Bay can again become a breeding ground for post-monsoon depressions and cyclones. The crucial difference is that one cannot equate every circulation entering the Andaman Sea with a cyclone threat to Odisha.

For now, the larger atmospheric signal suggests a system that may struggle against the emerging continental flow rather than reproduce the September 23 track.

The wind has changed — and the monsoon song is nearing its end

The bigger weather story may therefore not be the new circulation at all.

It is the wind reversal taking place over the Indian subcontinent.

The monsoon survives on a broad moisture-bearing circulation. But as the season advances, an anticyclonic circulation develops over northwestern and central India, while dry continental air begins travelling southwards and eastwards.

The 850-hPa wind pattern is particularly revealing.

Instead of the familiar monsoon flow carrying moisture from the Arabian Sea and Indian Ocean into the subcontinent, northwesterly and northerly winds begin taking control across the interior.

In simple terms, the atmosphere is beginning to change its direction.

The continental winds are now knocking at India's eastern door.

The Arabian Sea is losing its dominant monsoon connection with the interior, while the Bay of Bengal too is entering a more transitional regime. The result is a gradual weakening of the southwest monsoon circulation across central and eastern India.

The present model signal suggests that this transition could accelerate across the belt from Maharashtra towards Odisha around the beginning of October.

But there is an important technical caveat: IMD does not declare monsoon withdrawal merely from a wind-direction change on one forecast chart. Its operational criteria include sustained cessation of rainfall, establishment of an anticyclone in the lower troposphere, reduction in atmospheric moisture and spatial continuity of these conditions. IMD also notes that complete withdrawal from the country is considered only after October 1 when the circulation changes from the southwest-wind regime.

Therefore, the present forecast should be read as an early signal of the withdrawal phase, rather than an official IMD withdrawal declaration.

The implication is nevertheless significant: the monsoon song is entering its final movement over Odisha.

And when that song stops, Odisha may not immediately hear the sound of cool weather.

Monsoon retreats, but Odisha may sweat through early October

This is where the weather story takes an unexpected turn.

One might assume that the arrival of dry continental winds after the monsoon would immediately make Odisha cooler, drier and more comfortable.

It may not.

The first half of October could instead bring a familiar but uncomfortable combination: sunny skies, high humidity, weak local winds and temperatures remaining elevated – the classic ingredients of Odisha's October heat.

Why?

Because Odisha will be sitting on the eastern edge of the continental transition.

The monsoon may retreat from the region, but the atmosphere and land surface will still be carrying an enormous amount of moisture after months of rainfall. Rivers, wetlands, agricultural fields and saturated soils continue to feed moisture into the lower atmosphere.

If the large-scale winds become weak over Odisha while skies clear, solar heating can become intense.

The result is a peculiar weather equation:

wet ground + strong sunshine + weak winds + trapped moisture = oppressive October afternoons.

This is why temperatures need not immediately fall simply because the southwest monsoon has withdrawn.

Instead, the first part of October could feel muggy, sticky and sweaty, particularly during the afternoon and early evening.

The problem is not simply the thermometer.

It is the combination of temperature and humidity.

When humidity is high, sweat evaporates more slowly. The body therefore loses less heat through evaporation, making an otherwise moderate temperature feel considerably more oppressive.

This is the atmospheric recipe behind Odisha's familiar "October heat".

The real relief may arrive only after mid-October

The weather should become more comfortable only when the continental flow becomes sufficiently established to push dry air deeper into eastern India.

As the northwesterly/northerly circulation strengthens, moisture in the lower atmosphere should gradually decline. Dew points can fall, evening temperatures can become more comfortable and the sticky maritime feel can finally begin to disappear.

That transition is unlikely to be instantaneous.

So Odisha could see a split October:

Early October: monsoon withdrawal, weak winds, sunshine, high humidity and sweaty afternoons.

Around mid-October onward: increasing influence of dry continental air, falling moisture and progressively more comfortable conditions.

But there remains one major wildcard – the Bay of Bengal itself.

Even after the southwest monsoon retreats, October remains a climatologically active month for post-monsoon weather systems. A sufficiently favourable circulation over the Bay can bring moisture back towards the Odisha coast and temporarily interrupt the emerging dry pattern.

So the withdrawal of the monsoon does not mean the Bay has gone silent.

It means the weather rulebook has changed.

The September 23 deep depression demonstrated how quickly a tropical system can turn a moisture-rich monsoon atmosphere into a flood-producing event across Odisha.

The weather maps now show the opposite process beginning: continental winds pushing the monsoon away.

The question for October, therefore, may not simply be whether another cyclone forms.

It may be whether the changing winds can keep the Bay's next disturbance away from Odisha – while leaving the state trapped between departing monsoon moisture and incoming continental heat.
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