India Monsoon 12 June 2026 — Sub-seasonal Outlook: Arabian Sea Stalls, Bay of Bengal Surges
Eight days after Kerala onset, the Southwest Monsoon has declared over Goa (7 June), coastal Karnataka (11 June), and Maharashtra (10–11 June). The next 10 days present a diverging two-branch picture: a weakening, anticyclonically disrupted Arabian Sea current is expected to slow West Coast advance, while the Bay of Bengal branch remains robust, sustaining active-to-vigorous conditions across the Northeast, Bengal, and progressively East-Central India.
Arabian Sea Branch
Bay of Bengal Branch
Peak Rain Activity
IMD Position — 12 June 2026
IMD has declared monsoon onset over all West Coast states through Maharashtra, and advance into West Bengal and Bihar by 11–12 June. Warnings of heavy to very heavy rainfall at isolated places have been issued over Northeast India, Sub-Himalayan West Bengal, and Odisha through 14 June. Conditions remain favourable for further advance into Odisha, Chhattisgarh, and Jharkhand over the next 2–3 days. Rajasthan has recorded 154% excess pre-monsoon rainfall — attributed to successive western disturbances, not monsoon advance.
VayuMet-GFS Sub-seasonal Analysis
The following maps are generated from VayuMet's GFS model run initialized 12 June 2026 at 00 UTC, using forecast fields through 21 June (10-day window). Rainfall is derived from accumulations over the days; 850 hPa wind from isobaric pressure level output. Anomalies are computed against the 1991–2020 long-term mean (LTM) for corresponding calendar days.
Fig. 1 — Cumulated Rainfall (top) and Anomaly vs 1991–2020 Long Term Mean (bottom) · Day 1–5 left, Day 6–10 right · GFS IC: 12 Jun 2026 00 UTC
Fig. 2 — Mean 850 hPa Wind Speed (top) and Wind Anomaly vs Long Term Mean (bottom) · Day 1–5 left, Day 6–10 right · GFS IC: 12 Jun 2026 00 UTC
Region-wise Analysis
Arabian Sea & West Coast — Onset Stalling
The Day 1–5 wind anomaly (Fig. 2, bottom-left) shows a strong negative wind speed anomaly over the central and north Arabian Sea, combined with an anticyclonic anomalous flow. The low-level southwesterly jet is disorganised and well below the speed needed for sustained northward advance — pointing to a stall at the current monsoon limit (Konkan Maharashtra) through ~16 June. This is consistent with below-Long Term Mean rainfall over the West Coast interior and peninsular interior (red anomaly patch in Fig. 1, bottom-left).
In Day 6–10 the negative Arabian Sea anomaly weakens but does not fully reverse (Fig. 2, bottom-right). Some recovery of southwesterly flow is evident, and the possibility of a renewed West Coast push — toward Gujarat and coastal Madhya Pradesh — opens toward the end of this window. The 21–25 June period is the key reassessment point.
Bay of Bengal, Northeast & East-Central India — Active to Very Active
Day 1–5 cumulated rainfall (Fig. 1, top-left) shows the heaviest accumulations over Northeast India, Sub-Himalayan West Bengal, and the Odisha coast, with anomaly above Long Term Mean across this belt. The positive wind anomaly over the BoB (Fig. 2, bottom-left) confirms enhanced moisture transport northwestward into eastern India.
Heavy to very heavy rainfall at many places is expected over Northeast India and Sub-Himalayan West Bengal through Day 5 (16 June). Rainfall activity escalates sharply from 17 June onward — extremely heavy to exceptionally heavy rainfall at isolated places over Assam, Meghalaya, Arunachal Pradesh, and Sub-Himalayan West Bengal marks the peak intensity phase (Days 6–8, 17–19 June). Widespread heavy to very heavy rain continues across most districts of the Northeast through this period, with a gradual easing expected from 20 June.
Flood watch — Northeast India (17–19 June): Brahmaputra and Barak valley districts of Assam, Meghalaya highlands, and Arunachal Pradesh foothills face elevated flooding and landslide risk during the peak activity phase. Monitor IMD and NDRF advisories.
South Peninsula
Below-Long Term Mean rainfall over the Karnataka, Andhra Pradesh, and Telangana interior in Day 1–5 — a direct consequence of the suppressed Arabian Sea westerly. Tamil Nadu coastal districts see near-normal conditions via BoB easterly moisture. Gradual improvement is expected in Day 6–10 as the Arabian Sea anomaly partially relaxes.
North & Northwest India — Pre-Monsoon Thundershowers
North and Northwest India remain firmly in pre-monsoon territory through both periods. Rajasthan — especially eastern districts and the Shekhawati belt — will continue to see thunderstorm activity with squalls (50–60 km/h), lightning, and isolated heavy rainfall driven by western disturbance-trough interaction. This pre-monsoon convective activity will persist through mid-June and is not indicative of monsoon advance.
VayuMet Outlook — 12 to 21 June
The 10-day picture is a split-branch monsoon regime. The Arabian Sea branch is suppressed — anticyclonic wind anomaly disrupts the westerly jet, West Coast advance stalls, and West Coast and peninsular interior rainfall will remain below Long Term Mean through ~16 June. The Bay of Bengal branch is vigorous and stable — active-to-very active monsoon over Northeast India and East-Central India, peaking to extremely heavy rain activity over most of the northeastern states during 17–19 June. Rajasthan and NW India will see continuing pre-monsoon thundershowers. Post 17 June, the Arabian Sea anomaly begins to weaken — if recovery is sufficient, resumption of West Coast advance toward Gujarat may become possible toward 20–21 June, but this remains conditional and will be assessed in the next update.
Watch points: (1) Arabian Sea westerly recovery after 17 June — determines West Coast advance timeline. (2) Peak BoB rain activity 17–19 June — flooding risk over Northeast India. (3) Pre-monsoon thunderstorm frequency over Rajasthan — monitor for severe squall events.
⚠ Disclaimer — VayuMet-GFS vs IMD
VayuMet's analysis is based on NOAA GFS model output and represents independent meteorological assessment — it is not an official IMD product. Where VayuMet's analysis on monsoon advance timing, Arabian Sea branch intensity, or regional rainfall outlook differs from IMD's official position, IMD should be treated as authoritative for all official purposes including government advisories, agricultural decisions, and disaster preparedness. GFS sub-seasonal forecasts beyond 5 days carry increasing uncertainty. Always cross-reference with IMD's latest bulletins at mausam.imd.gov.in.