Monsoon Exit Meets Resistance: Bay Storm Targets Andhra Coast by 25 September

The monsoon is finally packing up. IMD expects withdrawal to commence from southwest Rajasthan on 19 September, and this run backs it: pressure rising over the northwest, and ten straight days without a single rain alert anywhere in Rajasthan. But the season is not being allowed to leave quietly. A tropical system takes shape over the Andaman Sea around 20 September, tracks west-northwest across the Bay, and closes on the north Andhra Pradesh–south Odisha coast with landfall expected by 25 September — carrying gusts in the 95–105 km/h range and Extremely Heavy Rain that drives deep inland over the Bastar plateau.

The Quiet Exit: Rajasthan Goes Dry

Mean Sea Level Pressure and anomaly vs 1981–2010 NCEP R2 LTM · GFS IC 17 Sep 2026 00 UTC · Left: 17–21 Sep · Right: 22–26 Sep

The 17–21 September panel shows a positive Mean Sea Level Pressure (MSLP) anomaly of +2 to +5 hPa draped across Rajasthan and the northwest — the monsoon low filling in, exactly as withdrawal requires. The rainfall side agrees emphatically: northwest India stays blank on both five-day panels, and the district data returns not a single rain alert anywhere in Rajasthan across the full ten days. Rising pressure and a rain shadow that simply refuses to break is the signature IMD's withdrawal criteria are built to detect.

First, the Odds: What September Usually Delivers

Before reading too much into one model run, the climatology is worth knowing. The North Indian Ocean produces roughly five Cyclonic Storms a year — about 7% of the global total — with the Bay of Bengal outproducing the Arabian Sea about four to one. But the season is bimodal: the peaks sit in May and again in October–November, on either side of the monsoon.

September falls in the trough between them, for a specific reason: monsoon-season vertical wind shear tears at developing systems and caps their intensity. So September's Bay systems are plentiful but usually modest — most top out as Low Pressure Areas, Depressions or Deep Depressions rather than Cyclonic Storms. What they lack in wind they make up in water: the classic September system crosses the coast and grinds west-northwest inland for days, and the rainfall writes the headlines. That is precisely the shape of this run.

The Loud Arrival: Track, Strength, Landfall

Date	Where	What the model shows
20–22 Sep	Andaman Sea	System takes shape; Isolated Heavy Rain over South Andaman, gusts 50–55 km/h
23 Sep	Central/west Bay	Tracks west-northwest; first Heavy Rain on the Andhra coast, gusts building at Srikakulam
24 Sep	Closing on north Andhra–south Odisha coast	Coastal impacts peak in the model: gusts 95–105 km/h at Srikakulam, 80–95 km/h at Gajapati, Vizianagaram and Ganjam; Isolated Extremely Heavy Rain at Vizianagaram
25 Sep	Coast → Bastar plateau	Landfall by this date (IMD expectation). Scattered Extremely Heavy Rain over Bastar, Dantewada, Narayanpur and Kondagaon; gusts still 85–90 km/h
26 Sep	Telangana → Vidarbha	Weakening inland; Scattered Very Heavy Rain over Chandrapur, Gadchiroli and Bijapur; gusts 80–86 km/h

Model guidance only — verify against latest IMD bulletins.

On timing: IMD expects landfall by 25 September; this run's heaviest coastal signal lands slightly earlier, on 24 September. Read it as a 24–25 September landfall window that will tighten with each new run.

On strength: the model's peak gusts of 95–105 km/h at Srikakulam on 24 September imply, using the standard gust-to-sustained ratio (gust ≈ 1.3–1.5× sustained), sustained winds in the 65–80 km/h range — broadly consistent with Cyclonic Storm criteria (62–87 km/h). IMD has issued no classification as of 17 September, and none is implied here: nothing has formed yet. Treat it as a plausible upper bound from a single 10-day run, against a climatology that says September systems usually land softer.

The Real Story Is the Water

Cumulated Rainfall (mm) and anomaly vs 1991–2020 LTM · GFS IC 17 Sep 2026 00 UTC · Left: 17–21 Sep · Right: 22–26 Sep

The 22–26 September panel is unmistakable: a dense band of cumulative rainfall running inland from the north Andhra coast across Bastar into Vidarbha, carrying one of the largest positive rainfall anomalies of the season. Within it, Bastar draws the run's heaviest daily signal — Extremely Heavy Rain on 25 September. Northwest India stays blank on both panels. Two seasons, one map.

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